To see the other types of publications on this topic, follow the link: CFRP structure.
Dissertations / Theses on the topic 'CFRP structure'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'CFRP structure.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Nguyen, Phi Long. "Experimental and numerical study on thermo-mechanical behaviour of carbon fibre reinforced polymer and structures reinforced with CFRP." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1130/document.
Full textAbstract:
Le polymère renforcé de fibres de carbone (CFRP) est l'une des solutions courantes pour réparer/renforcer/ fortifier/ rétrofiter les structures en génie civil en raison de ses avantages dans les propriétésmécaniques, la durabilité et la maniabilité. Cependant, des problèmes d'incendie récents ont soulevédes inquiétudes quant à la performance au feu du CFRP et des structures renforcées par CFRP. Dansla littérature, il existe plusieurs études sur l'évolution de la performance mécanique de CFRP et desstructures renforcées par CFRP pendant ou après l'exposition à différents niveaux de température quisont proches des températures obtenus durant un feu. Cependant, les résultats sont dispersés en raisonde la diversité des matériaux utilisés, de la différence dans les protocoles d'essai et de la limitation del'installation d'essai pour une utilisation à température élevée. Des études analytiques et numériquessont également menées avec une étude paramétrique pour observer, améliorer et proposer desrecommandations pour les directives de conception. Cependant, le manque de données expérimentalesa une influence significative sur applicabilité des résultats disponibles.Cette recherche caractérise les comportements des CFRP et de la structure renforcée avec du matériauCFRP dans trois conditions distinctes concernant la température élevée et la charge mécanique quisont proches des différents cas d'application au feu. Les méthodes expérimentales et numériques sontutilisées pour mener cette recherche afin d'étudier plus en détail l'état de chaque matériau au cours desétudes de cas. En particulier, l'essai résiduel est utilisé pour étudier la performance mécanique desspécimens refroidis après exposition à température élevée en respectant l'évaluation du comportementrésiduel des structures renforcées en CFRP en situation post-incendie à des fins de réparation /renforcement. Deux essais thermomécaniques sont utilisés pour étudier la performance mécanique deséchantillons à différentes températures élevées et leur performance thermique à différents étatsmécaniques en respectant la situation d'incendie pour la prédiction et la conception. Les deux dernierscas portent sur l'influence de l'ordre de chargement sur les résultats pour confirmer la validité desdonnées mécaniques expérimentales obtenues à différentes températures lors de l'évaluation de laperformance au feu de la structure renforcée par CFRP où les effets mécaniques et puis les effetsthermiques sont combinés.Dans la première partie expérimentale, 86 essais sur deux types de CFRP (un préfabriqué en usine etun fabriqué manuellement en laboratoire) ont été étudiés dans la plage de température de 20°C à712°C. La performance du matériau CFRP est généralement réduite lorsque la température augmente.Les résistances thermomécaniques et résiduelles du P-CFRP diminuent graduellement de 20°C à700°C, tandis que le module de Young varie de moins de 10% de 20°C à 400°C et ensuite diminuesignificativement à 600°C. La performance thermomécanique identifiée de CFRP a été inférieure quesa performance résiduelle, en particulier à une température supérieure à 400°C. En outre, latempérature élevée et la charge mécanique sont expérimentalement pertinentes et l'ordre dechargement a donc un faible effet sur les performances du matériau dans des conditionsthermomécaniques. Un nouveau modèle analytique, proposé pour l'évolution de la résistance ultimethermomécanique en fonction de la température, a montré sa capacité à s'adapter à deux CFRP étudiéset à ceux testés dans des conditions thermomécaniques similaires dans la littérature [etc...]<br>Carbon fibre reinforced polymer (CFRP) is one of common solutions in repairing / reinforcing/strengthening/ retrofitting structures in civil engineering due to its advantages in mechanicalproperties, durability and workability. However, recent issues have raised concerns for fireperformance of CFRP and CFRP reinforced structures. Throughout the literature, there are severalinvestigations on the evolution of mechanical performance of CFRP and CFRP reinforced structuresduring or after exposing to different levels of temperature which are close to temperatures obtainedduring a fire. However, the results are scatter due to the diversity of materials used, the difference intest protocols, and limitation in test facility for elevated temperature use. Analytical and numericalstudies are also conducted with parametric investigation to observe, improve, and proposerecommendations for design guideline. Additionally, missing gap in experimental data has asignificant influence on the applicability of the available results.This research characterizes the behaviours of CFRPs and of concrete structure reinforced with CFRPmaterial under three separated conditions concerning elevated temperature and mechanical loadingthat are close to different cases of fire application. The experimental and numerical methods used inthis research are to further investigate the status of each material during the case studies. Particularly,residual test is used to study the mechanical performance of specimens cooled after exposing toelevated temperature respecting the evaluation of the remained behaviour of CFRP reinforcedstructures at post-fire situation for repairing/ retrofitting purpose. Two thermo-mechanical tests areused to study the mechanical performance of specimens at different elevated temperatures and theirthermal performance at different mechanical statuses respecting the fire situation for predicting anddesigning purpose. The two final cases focus on the influence of loading order on the results toconfirm the validity of experimental mechanical data obtained at different temperatures whenapplying for evaluating the fire performance of CFRP reinforced structure where mechanical effectsand then temperature effects are combined.In the first experimental part, 86 tests on two types of CFRP (one pre-fabricated in factory and onemanually fabricated in laboratory) were studied in the temperature range from 20°C to 712°C. Theperformance of CFRP material is generally reduced as the temperature increases. The thermomechanicaland residual ultimate strengths of P-CFRP gradually decrease from 20°C to 700°C, whileits Young’s modulus varies less than 10% from 20°C to 400°C and then significantly decreases at600°C. The identified thermo-mechanical performance of CFRP was lower than its residualperformance, especially at temperature beyond 400°C. Furthermore, the elevated temperature andmechanical load are experimentally shown to be relevant and thus the loading order has a small effecton the material performance under thermo-mechanical conditions. A new analytical model, proposedfor the evolution of thermo-mechanical ultimate strength in function of temperature, has shown theability to fit with two studied CFRPs and with those tested under similar thermo-mechanical conditionin the literature [etc...]
2
Grilli, Sofia. "Bond behavior between CFRP and masonry substrate determined by double-lap shear tests." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Find full textAbstract:
Twenty double-lap shear tests are set up to evaluate the bond properties of interfaces uniaxial Carbon Fiber Reinforced Polymer (CFRP) strips as overlays on unreinforced masonry wall prisms. The efficient use of the material significantly depends on the bond between the externally bonded sheet and the substrate material since a premature debonding of the objects involved may lead to a premature failure of the system and, thus, to a low degree of exploitation of the fibrous structure.
In the test both the length and the width of the CFRP sheets are considered in order to analyse the mechanical behaviour of the specimens changing those parameters. In the first part of the research the background of the test and the materials used for the experimental campaign are presented while the second part is more focused on the technical procedure of the double-lap shear tests setting up. The results obtained with these experiments are then plotted to have a full understanding of the behaviour of the materials used in this specific scenario.
3
Yuan, Chen. "Crushing Responses and Design of CF/EP Composite Structures." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/20581.
Full textAbstract:
By virtue of their excellent properties of specific strength-to-mass and stiffness-to-mass ratios, carbon fibre reinforced epoxy (CF/EP) structures are becoming increasingly important in various transportation tools and industrial machines. Many studies have investigated the damage responses of CF/EP composite structures. However, there are still outstanding issues associated with failure-mechanism investigation and design for CF/EP composite structures under crushing loading. First, specific experimental approaches and advantageous models remain inadequate. Second, systematic study of the crushing responses of CF/EP composite structures is necessary. Third, the structural design of CF/EP materials are meaningful but seldom. Transverse impact is a common and important crushing scenario for CF/EP composite sandwich panels (CSPs). This study developed a specific FEA model addressing intralaminar damage, interlaminar and adhesive delamination, and honeycomb core (HC) failure of CF/EP CSPs, and designed an optimal structure under both transverse normal and oblique impact. Next, in-plane crushing responses of the CF/EP CSPs were investigated. Both in-plane localised and globalised crushing tests were conducted to characterise the failure responses and mechanisms of CSPs. CF/EP composite tubes are very promising for crushing energy absorption. This study investigated the failure mechanism and energy absorption of CF/EP tubes under three triggering initiators subjected to both quasi-static and dynamic crushing. This study characterised the failure responses and mechanisms of CF/EP composite structures under different crushing scenarios, and numerical techniques were applied. Optimisation theories with mathematic algorithms were utilised to improve the models’ comprehensive performance. The findings provide a series of valuable data for potential engineering applications.
4
Boháčová, Marie. "Návrh sondy vířivých proudů a její aplikace pro zkoušení kompozitních leteckých konstrukcí." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-364595.
Full textAbstract:
This thesis deals with design of an eddy current transducer which enables non-destructive inspection of composite aircraft structures primarily carbon fiber reinforced plastic (CFRP) in areas of manufacture and maintenance. The design of the transducer is based on analytical-experimental approach and its electrical and mechanical parameters were optimized to ensure a good signal to noise ratio at the six composite samples. These samples contain artificial discontinuities in the form of various types of defects. These defects are simulating the various types of damage created in the aircraft structure, especially delamination or thickness changes of composite materials. The experimental measurements, data collection and non-destructive evaluation were performed during the period. The result of this work is functional eddy current probe, which is reliably able to detect some damage of the carbon composite structures to the depth of 3,9 mm.
5
Yee, Jeffrey Cheze Hui. "Thin CFRP composite deployable structures." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614308.
Full text
6
Karlsson, Marlene. "CFRP strengthening of existing building structures." Thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-96306.
Full textAbstract:
Most of the building structures needed in twenty years from now is already built. Building structures are ageing and they deteriorate and often the demands on the structure changes over time. It is often needed to reinforce the structure, especially when reconstructing, repairing or renovating a building. The traditional strengthening methods that are used today are strengthening the structure with beams and columns of steel. The beams and columns often require much space and problems might occur if there are a lot of installations. There is another more modern technique where a composite plate, sheet, grid or bar of relatively small thickness is bonded with an epoxy adhesive to the structure. These reinforcements don’t change the cross-section of the structure. The most common type of fibre reinforcement that is used for strengthening in the building industry is carbon fibre. The carbon fibre products are much more expensive when comparing to steel. Therefore the object of this report is to show when it is economically motivated to use carbon fibre instead of the more traditional material steel. To do this I have studied five real cases brought to me by WSP Construction in Linköping, Sweden. The study shows that in the cases where it’s possible to use composites strengthening the building structure it is also economically motivated to do so. Even if the material is more expensive than the more traditional materials the total cost is in the same price class as the traditional ones because of the short time of construction. But there is still a problem with only a few consultants and entrepreneurs that have the knowledge and the experience to work with composites when strengthening a structure. If the knowledge will be spread to the consultants I will say that carbon fibre composites are the materials of tomorrow even in the building industry.<br>En stor del av det byggnadsbestånd som kommer att behövas inom en tjugoårsperiod är redan uppfört idag. Byggnadskonstruktioner åldras och försämras, och ofta förändras förutsättningarna för byggnaderna med tiden. Ett ständigt återkommande moment är behovet av att förstärka den bärande konstruktionen, framför allt i samband med ombyggnation, reparation och renovering. De traditionella metoder man använder sig av idag innebär att stålbalkar och pelare monteras för att förstärka konstruktionen. Dessa tar utrymme i anspråk och problem kan uppstå med t ex installationer i tak. En nyare metod innebär att man fäster kolfiberkompositer på ytan av konstruktionen i tunna lager i form av laminat, väv, nät eller stavar som fräses ner i ytan. För att fästa kompositen på ytan använder man sig av epoxi. De tunna lagren gör att konstruktionens tvärsnitt och egenvikt inte förändras märkbart. Då kolfiber är ett dyrare material än stål är syftet med denna rapport att ta fram konkreta praktikfall där det är ekonomiskt motiverat att använda sig av kolfiberkompositer istället för de traditionella metoder som används idag. Fem praktikfall tillhandahållna av WSP Byggprojektering i Linköping har studerats. Det visade sig att i de fall det var tillämpligt att använda sig av kolfiber för förstärkning var det även ekonomiskt hållbart. Trots det dyrare materialet innebär den korta monteringstiden att totalkostnaden för förstärkningsjobbet ligger i ungefär samma prisklass som en förstärkning med stål. Problem kvarstår dock med alltför några kunniga konstruktörer och entreprenörer – men annars är kolfiberkompositen morgondagens material.
7
David-West, Opukuro Sunday. "Low velocity impact studies on CFRP composite structures." Thesis, University of Strathclyde, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428854.
Full text
8
James, Valontino Ruwhellon. "Fatigue Behaviour of CFRP Strengthened Reinforced Concrete Beams." Master's thesis, Faculty of Engineering and the Built Environment, 2020. http://hdl.handle.net/11427/32274.
Full textAbstract:
The performance of reinforced concrete (RC) structures, such as bridges in the heavy haul industry, may be severely impacted by fatigue when subjected to repeated cyclic loading. Fatigue not only reduces load carrying capacity and serviceability limit states (SLS), but it can cause structural failure even when the components are subjected to low stress range cyclic loading. Corrosion damage exacerbates fatigue related problems as chloride induced pitting corrosion facilitates the formation and gradual propagation of cracks under cyclic loading. A common rehabilitation and retrofitting approach that involves patch repairing and fibre reinforced polymer (FRP) strengthening has proven effective to not only restore structural capacity, but also to enhance infrastructure service life. The structural repair process involves the replacement of deteriorated cover concrete with a less permeable patch repair mortar. The patch repair only restores durability of the structure; to restore or enhance structural capacity the repair process further involves bonding of FRP laminates. Particularly in the case of FRP's with a low elastic modulus, the design is often guided by serviceability limit states as opposed to ultimate limit states (ULS), resulting in an over-reinforced structural member. In addition, the reinforcement area of commercially available FRP strengthening may exceed the design requirements, especially at low levels of corrosion damage. In both the abovementioned considerations the design may result in an over-reinforced section. At the time when this researched was proposed, the effect of increasing damage extent on fatigue behaviour of over-reinforced RC beams was not clear and merited further investigation. A scientific experimental approach was developed to investigate the long-term performance of fifteen (15) full-scale 40MPa RC beams with dimensions 155x254x2000mm and ultimate capacity of 62.3kNm. Accelerated corrosion damage was induced in varied extents which included 450mm, 800mm, 1300mm and 1800mm length to a constant degree of 10% on all specimens. Specimens from each damage extent were patch repaired using SikaCrete214 and subsequently strengthened with externally bonded with SikaCarboDurS512 carbon fibre reinforced polymer (CFRP) laminates. Four-point bending monotonic loading tests were conducted on one (1) specimen from each damage extent. The results obtained from the quasi-static tests were used to determine two (2) cyclic loading stress ranges at which the remaining 2 specimens from each damage extent would be tested under. Under the 40% and 60% stress ranges four-point bending cyclic loading tests were carried out at a test frequency of 4Hz. Information was acquired on key performance indicators that included fatigue life, crack development, failure mode and stiffness degradation, where stiffness was assessed in terms of midspan deflection, composite material strains and neutral axis shift. Information on these parameters were collected using strain gauges, linear variable differential transducers (LVDT), DEMEC strain targets and digital image correlation (DIC). Ultimate failure loads under monotonic loading showed that despite having the highest degree of corrosion, the 450mm damage extent specimen had the highest failure load of 325kN. The failure load gradually reduced to 290kN as the damage extent was increased to 1800mm and the 0mm (control) specimen failed at the lowest load of 274kN. In contrast to the static behaviour, the specimen fatigue life enhanced by 106.3% as the damage extent was increased from 450mm to 1800mm. As expected, the 40% stress range tests yielded much longer fatigue lives than their 60% stress range counterparts. Furthermore, the experimentally obtained fatigue lives were compared to three fatigue life prediction models and the Helgason and Hanson model yielded the closest correlation with the experimental results. IV ABSTRACT Crack densities were found to increase with a longer fatigue life. An increase in damage extent was found to positively affect crack development and overall stiffness of the specimen during longterm fatigue testing. This finding was further substantiated by an assessment of midspan deflection, compression concrete strain and carbon fibre strain results, which all suggested a lower neutral axis and a lower stiffness reduction rate under fatigue loading as the damage extent was increased from 450mm to 1800mm. Furthermore, the tension concrete cracks propagated gradually during longer fatigue tests periods, while the tension steel and carbon fibre were comparably less affected by the resultant internal forces. Unfortunately, the neutral axis strain measurements using DEMEC targets were unable to assess the relative effect of an increase in damage extent as well as the compression concrete and carbon fibre strains were able to. During this experimental period, it was established that the laboratory layout was not conducive for carrying out the DIC process of long-term cyclic loading tests. The area in which testing took place did not adequately protect the camera against the environment and therefore required daily storage of the equipment. Regular movement of the camera for storage purposes introduced measurement inaccuracies which accumulated over longer test periods of up 20 days. However, for the short-term tests that did not require movement of the camera, the DIC process yielded favourable results. It was possible to capture the crack patterns early in the test period when the crack growth rate and development of new cracks was high using DIC. It was found that the high strain cracks coincided with the points of maximum vertical deflection (obtained through DIC) and eventual failure location of the specimen. The points of maximum deflection obtained from the DIC process were often not at midspan, which in the absence of the DIC process, would not have been possible to predict accurately. The results have shown that the specimens with the longer damage extents exhibit improved fatigue performance than their shorter counterparts. This revealed a stark contrast to their monotonic loading performance which favoured shorter damage extents. Furthermore, DIC holds potential to predict failure location more accurately than conventional approaches used for structural health monitoring (SHS).
9
Khechen, Aris. "Study of adhesively bonded repairs in aircraft CFRP primary structures." Master's thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/31585.
Full textAbstract:
Afin de développer un protocole d’essai standardisé et des outils analytiques facilitant la conception de réparations collées en biseau pour des structures composites aéronautiques primaires, le présent mémoire se concentre sur la caractérisation et la modélisation des performances de joints collés en composite de type lisse-escalier soumis à un effort de traction uni-axiale. Dans un premier temps, deux matériaux composites tissés, une toile (PW) et un satin (8-HS) pré-imprégnés de type plastique à renfort de fibre de carbone ont été testés en traction uni-axiale à température ambiante sec (TAS) et à température élevée sec (TES). Les données issues de cette caractérisation ont permis la modélisation numérique des réparations. Dans un deuxième temps, des réparations de type lisse-escalier ont été fabriquées sur des stratifiés en utilisant les matériaux composites PW et 8-HS en suivant la même séquence de plis quasi-isotrope ([+45°/0°/-45°/90°]2s) pour le parent et pour la réparation. Le film adhésif utilisé est le Cytec FM300-2M. L’effet des conditions environnementales et de l’angle de biseau (3°, 5.5° et 7.5°) sur les performances des réparations a été étudié. Les résultats des essais de traction ont révélé que l’angle de biseau a un impact significatif sur le mode de rupture de la structure réparée. Alors que la rupture s’est produite dans le composite pour les réparations avec un angle de biseau de 3°, une rupture en cisaillement de type cohésive a été observée pour les réparations pour les biseaux à 5.5° et 7.5°. Ce changement de mode de rupture a été retrouvé pour les deux conditions environnementales (TAS et TES). Comparativement au stratifié intact, une baisse non-significative de la rigidité a été notée pour tous les angles de biseau. Toutefois, l’augmentation de l’angle de biseau a conduit à une baisse significative de la restitution de la contrainte à la rupture comparativement à celle du stratifié d’origine, indiquant l’importance de l’angle de biseau sur l’intégrité de la structure des réparations adhésives de type lisse-escalier. Les essais de tractions à TES suggèrent qu’il n’y a qu’une très faible diminution de la rigidité et de la contrainte à la rupture pour les réparations à TES comparativement à TAS. Finalement, des analyses par éléments finis 2D dans l’épaisseur ont été conduites en utilisant ABAQUS Standard et Explicit. Une analyse élastique a tout d’abord été menée afin de prédire les distributions des contraintes de pelage et de cisaillement normalisées au milieu de l’adhésif, le long de la ligne adhésive, pour trois différentes configurations géométriques de jointure (lisse-lisse, lisse-escalier, escalier-escalier). Contrairement aux distributions de contraintes uniformes observées le long de la ligne adhésive de la configuration lisse-lisse, de forts et fréquents pics de contraintes de pelage et de cisaillement ont été observés pour les deux autres configurations. Ces observations ont mené à conclure que la modélisation d’un joint de réparation collé en biseau doit être conduite avec précaution. Émettre l’hypothèse que la surface adhésive du stratifié patch est lisse (i.e.: configuration lisse-lisse) alors qu’elle est en fait de type lisse-escalier implique de ne pas prendre en compte les pics de contraintes causés par les irrégularités géométriques de la surface adhésive du stratifié. Cela peut mener à la surestimation de la contrainte à la rupture de la réparation. Pour finir, une analyse élastique-plastique a été conduite en utilisant les modèles de plasticité et d’endommagement par cisaillement déjà implémentés dans ABAQUS. Ces modèles de plasticité et d’endommagement ont été utilisés pour le film adhésif seulement. Le matériau composite a été supposé linéaire élastique jusqu’à la rupture. Le critère des déformations maximales a été utilisé pour prédire la rupture du premier pli dans le composite. Les prédictions obtenues avec le modèle et les résultats expérimentaux ont montré de très bonnes corrélations.<br>This master’s degree thesis focuses on testing and modeling the bonded scarf-stepped composite joint performance under uniaxial tensile loading as part of the effort to develop testing protocols and analytical tools for the design of scarf bonded repair for primary aeronautical composite structures. First, plain weave (PW) and 8-harness satin (8-HS) carbon fiber-reinforced plastic (CFRP) pre-preg composite materials were tested under uniaxial tensile loading at room temperature dry (RTD) and elevated temperature dry (ETD) conditions. The gathered characterization data was later used for the numerical modeling of the repairs. Furthermore, smoothed parent laminate bonding surface and stepped patch laminate bonding surface (scarf-stepped repairs were performed using both PW and 8-HS composite materials with matching quasi-isotropic ([+45°/0°/-45°/90°]2s) ply stacking sequence between the parent and the patch. The adhesive film that was used is the Cytec FM300-2M. The effects of environmental conditions and the influence of the scarf angle (i.e. 3˚, 5.5° and 7.5˚) on the performance of the bonded repairs were investigated. The tensile test results revealed that the scarf angle has a significant impact on the failure mode of the repaired composite part. While substrate failure occurred with a 3˚ scarf angle, cohesive shear failure was observed for the 5.5° and 7.5˚ angles. This change in failure mode is consistent both at RTD and ETD. When compared with the pristine laminate, an insignificant drop in stiffness was found regardless of the scarf angle. Although, increasing the scarf angle led to a significant drop in strength restitution in comparison with the pristine laminate. This indicates the importance of the scarf angle on the structural integrity of a scarf-step bonded repair. The tensile test results in ETD conditions suggest a slight decrease in stiffness and strength for both materials at ETD. Eventually, 2D through-thickness finiteelement analyses were also conducted using both ABAQUS Standard and Explicit. An elastic analysis was first performed to predict the distribution of normalized shear and peel stresses in the middle of the adhesive along the bondline for three different joint geometries (scarf-scarf, scarf-step and step-step). As opposed to the uniform stress distributions found along the bondline of the scarf-scarf configuration, high and frequent peaks of peal and shear stresses were found for both scarf-step and step-step configurations. These observations led to the conclusion that one must be particularly cautious when modeling a scarf joint bonded repair. Assuming that the patch laminate bonding surface is smoothed (i.e., scarf-scarf configuration) while it is actually stepped (i.e., scarf-step configuration) can lead to overestimating the overall repair strength since the high stress peaks caused by the geometric irregularities of the stepped patch laminate bonding surface would then be ignored. Furthermore, an elastic-plastic analysis was conducted using the already implemented plasticity and shear damage models in ABAQUS. These plasticity and damage models were used for the adhesive film only. The composite material was supposed to behave linear-elastically up to failure. The maximum strain criterion was used to predict the first ply failure in the composite. The predictions obtained with the model correlated very well with the experimental results.
10
Chan, Yui Bun. "Investigation of cracked reinforced concrete framed structures repaired with CFRP /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202002%20CHAN.
Full textAbstract:
Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.<br>Includes bibliographical references (leaves 209-210). Also available in electronic version. Access restricted to campus users.
11
Marín, Hernández Lorena. "Hygrothermal effects on CFRP: testing, analysis and structural optimization." Doctoral thesis, Universitat de Girona, 2015. http://hdl.handle.net/10803/398412.
Full textAbstract:
In the common design and certification process, a large number of experimental tests, going from small specimens to the full structure, are performed. In these tests, the environmental conditions, especially temperature and humidity, which the structural component will be submitted are considered. This multiplies the number of tests to be performed. With the aim of reducing the economic cost and the time needed for the design and the certification of components, numerical tools that allow a reduction of experimental tests and help in the analysis of results, are developed. In this framework, the present thesis tackles the topic of hygrothermal effects in composite materials in both fields: experimental tests and numerical tools. Specifically, the thesis focuses its attention on two analysis levels which are seldom present in the scientific literature: the optimization of structural components and the experimental characterization of the translaminar failure of the material, both considering environmental changes<br>En el proceso habitual de diseño y certificación de componentes aeronáuticos se realiza un elevado número de ensayos experimentales que van desde pequeñas probetas hasta la estructura final. La consideración de las condiciones ambientales, especialmente temperatura y humedad, a las que el componente se verá sometido, incrementará el número de ensayos a realizar. Para disminuir el elevado coste y el tiempo de diseño y certificación, se desarrollan herramientas numéricas que permiten sustituir parte de los ensayos experimentales y facilitan el análisis de resultados. En este ámbito, la presente tesis enfoca la problemática de la consideración de los efectos ambientales tanto en los ensayos experimentales como en el desarrollo de herramientas numéricas. Concretamente, se centra en dos niveles de análisis con escasa o nula presencia en la literatura científica sobre efectos higrotérmicos: optimización de elementos estructurales considerando cambios ambientales y la caracterización experimental del fallo translaminar del material con variaciones higrotérmicas
12
Valdez, S. H. D. "Structural integrity monitoring of CFRP laminates using piezoelectric devices." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511369.
Full text
13
Suliga, Agnieszka. "Resistance of CFRP structures to environmental degradation in low earth orbit." Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/845096/.
Full textAbstract:
Within this study, a development of a protection strategy for ultra-thin CFRP structures from degrading effects of low Earth orbit (LEO) is presented. The proposed strategy involves an application of a modified epoxy resin system on outer layers of the structure, which is cycloaliphatic in its chemical character and reinforced with POSS nanoparticles. The core of the CFRP structure is manufactured using a highly aromatic epoxy resin system which provides excellent mechanical properties, however, its long-term ageing performance in space is not satisfactory, and hence a surface treatment is required to improve its longevity. The developed resin system presented in this thesis is a hybrid material, designed in such a way that its individual constituents each contribute to combating the detrimental effects of radiation, atomic oxygen (AO), temperature extremes and vacuum induced outgassing of exposed material surfaces while operating in LEO. The cycloaliphatic nature of the outer epoxy increases UV resistance and the embedded silicon nanoparticles improve AO and thermal stability. During the study, a material characterization of the developed cycloaliphatic epoxy resins was performed including the effects of nanoparticles on morphology, curing behaviour, thermal-mechanical properties and surface chemistry. Following on that, the efficacy of the modified resin system on space-like resistance was studied. It was found that when the ultra-thin CFRP structures are covered with the developed resin system, their AO resistance is approximately doubled, UV susceptibility decreased by 80\% and thermal stability improved by 20\%. Following on the successful launch of the InflateSail mission earlier this year, which demonstrated a sail deployment and a controlled de-orbiting, the findings of this study are of importance for the future generation of similar, but significantly longer missions. Ensuring resistance of CFRP structures in a highly corrosive LEO environment is a critical requirement to make their use in space applications truly feasible.
14
Hmidan, Amer. "Crack-Dependent Response of Structural Steel Members Repaired with CFRP." Diss., North Dakota State University, 2014. https://hdl.handle.net/10365/27562.
Full textAbstract:
Cracking of the lower flange in steel-girder bridges is a critical consideration because it will influence flexural behavior such as load-carrying capacity. Timely rehabilitation will save long-term repair costs and warrant sustainable performance. Carbon-fiber-reinforced polymer (CFRP) is a promising material to repair damaged steel members. This non-metallic reinforcement provides a number of benefits when compared to traditional repair materials (e.g., welded steel plates) for deteriorated steel girders: for example, a favorable strength-to-weight ratio, resistance to corrosion and fatigue, rapid installation in practice, and reduced long-term maintenance expenses. Although applying CFRP to steel members has recently attracted the rehabilitation community, its contribution to the behavior of repaired members is not fully understood. Very limited information about the interaction between the level of initial damage in steel girders and CFRP-repair is available, and also, scant research about the long-term performance and environmental durability for such repaired members has been done. This study addresses these identified research gaps based on a two-phase experimental program. The first phase focuses on CFRP-repaired steel beams having various levels of initial damage (representing multiple stages of fatigue crack propagation). The second phase is focused on testing the repaired beams when subjected to various levels of sustained intensity and cold temperature. A three-dimensional non-linear finite element (FE) model is developed to predict the flexural behavior of CFRP-repaired beams, including CFRP debonding and crack propagation across the critical section of the repaired beams. Also, the FE method is used and regression equations are proposed to predict the static strength of standard steel W Shapes repaired with CFRP, taking into consideration the material and geometric properties.
15
Kadhim, Majid. "Dynamic response of structural steel elements post-strengthened with CFRP." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/dynamic-response-of-structural-steel-elements-poststrengthened-with-cfrp(6e71c4d5-0bc5-4274-bd84-f99b0c966bb1).html.
Full textAbstract:
Structural elements in buildings and civil engineering infrastructure can often be vulnerable to various kinds of impact actions during their service life. These actions could result from various sources e.g. collision of vehicles, ships and vessels or falling masses in industrial buildings. Since, for various reasons, such accidental actions have not always been considered in the existing engineering design of buildings and civil engineering structures such as bridges etc., investigation of effective structural strengthening techniques is justified. As fibre reinforced polymer (FRP) composites have commonly been employed efficiently to strengthen steel members against static and fatigue loads, examining the FRP strengthening technique to enhance structural steelwork in impact situations is the main focus of this study. The research aims to experimentally investigate the dynamic behavioural response of axially loaded steel columns and steel beams strengthened with various carbon fibre reinforced polymer (CFRP) configurations. To achieve this goal, a series of experimental tests was implemented including testing a number of CFRP strengthened and unstrengthened steel beams and columns under static and impact loads. The experimental results show that CFRP can improve the global and local behaviour of steel members subjected to impact loads. This improvement varied depending on the CFRP configuration, the amount of CFRP and the pre-existing axial load value in the member. In order to examine all the parameters that can affect the dynamic behaviour of CFRP strengthened steel members in addition to those not included in the experimental programme, a comprehensive numerical simulation of the experimental work was carried out using a validated finite element model. Afterwards, an extensive parametric study was conducted to provide a comprehensive understanding of the behaviour of CFRP strengthened steel members subjected to impact load. The simulation results illustrate that the effectiveness of CFRP increases with high impact energies. The parametric study results have also revealed that the configurations and distributions of CFRP have a major influence on the effectiveness of the reinforcement. A detailed numerical assessment has also been performed to find the CFRP effectiveness when applied to full-scale steel columns. It has been found that strengthening with CFRP in practical quantities and configurations could prevent steel columns from failure under transverse impact loading. The strengthening effectiveness was found to be dependent on boundary conditions, impact velocity, impact mass, impact location, preloading level, impact direction, CFRP configuration, and the length and thickness of the CFRP. Based on the results obtained from the full-scale simulation, it has been found that the CFRP strengthening technique can be used efficiently and effectively at the scale of elements common in everyday building and infrastructure. This study also provides a useful database for different kinds of strengthening configurations, impact velocities and masses, boundary conditions, etc.
16
Tasligedik, Ali Sahin. "Lap Splice Behavior And Strength Of Cfrp Rolls." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609694/index.pdf.
Full textAbstract:
Behavior of lap splices formed by CFRP rolls has been studied. CFRP rolls have been prepared by using CFRP sheets of a certain width. Strengthening methods that use CFRP rolls as reinforcement may require an epoxy anchored lap splice due to the conditions at the strengthening regions. It may not always be possible to strengthen the region by using only one roll fan anchored at both ends, but using two rolls from opposite faces of the member and lap splicing them at the middle so that they act as a single roll. Lap splice behavior can be studied best by using flexural beam bond specimens if the reinforcing material is steel. Therefore, it has initially been suggested that flexural beam specimens reinforced for flexure with CFRP rolls as tension reinforcement can be used in studying the lap splice behavior. However, due to the difficulties encountered in the beam tests, another type of test specimen was introduced, which was a direct pull-out specimen. In this type of test specimen, lap spliced CFRP rolls have been tested under direct tension, in which the tension has been applied by making use of concrete end blocks that transfer the tension to the rolls. Eleven tests have been made in total. Full material capacity of the rolls could not be achieved due to premature failures. However, important conclusions and recommendations have been made for future studies.
17
Saeed, Yasir Matloob. "Behavior of Prestressed Concrete Beams with CFRP Strands." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/2726.
Full textAbstract:
The high cost of repairing reinforced or prestressed concrete structures due to steel corrosion has driven engineers to look for solutions. Much research has been conducted over the last two decades to evaluate the use of Fiber Reinforced Polymers (FRPs) in concrete structures. Structural engineering researchers have been testing FRP to determine their usability instead of steel for strengthening existing reinforced concrete structures, reinforcing new concrete members, and for prestressed concrete applications. The high strength-to-weight ratio of FRP materials, especially Carbon FRP (CFRP), and their non-corrosive nature are probably the most attractive features of FRPs.
In this study, an experimental program was conducted to investigate the flexural behavior of prestressed concrete beams pre-tensioned with CFRP strands. The bond characteristics were examined by means of experimentally measuring transfer length, flexural bond length, and bond stress profiles. A total of four rectangular beams pre-tensioned with one 0.5-in. diameter CFRP strand were fabricated and tested under cyclic loading for five cycles, followed by a monotonically increasing load until failure. In investigating bond properties, the experimental results were compared to the equations available in the literature.
The results from the four flexural tests showed that the main problem of CFRP strands, in addition to their liner-elastic tensile behavior, was lack of adequate bonding between FRP and concrete. Poor bonding resulted in early failure due to slippage between FRPs and concrete. As a result, a new technique was developed in order to solve the bonding issues and improve the flexural response of CFRP prestressed concrete beams. The new technique involved anchoring the CFRP strands at the ends of the concrete beams using a new "steel tube" anchorage system. It was concluded that the new technique solved the bond problem and improved the flexural capacity by about 46%.
A computer model was created to predict the behavior of prestressed beams pre-tensioned with CFRP. The predicted behavior was compared to the experimental results. Finally, the experimental results were compared to the behavior of prestressed concrete beams pre-tensioned with steel strands as generated by the computer model. The CFRP beams showed higher strength but lower ductility.
18
Carolin, Anders. "Strengthening of concrete structures with CFRP : shear strengthening and full scale applications." Licentiate thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17937.
Full textAbstract:
Structures can be in need of strengtheing due to many reasons, which are presented in this thesis. A literature review gives the existing methods for enhancing a structures load bearing capacity. In this thesis focus will be set at external bonding with carbon fibre reinforced polymers. A theory for shear strengthing is presented and compared to laboratory test. Full-scale applications with measurements are evaluated and presented. Finally, some topics for further research are given.<br><p>Godkänd; 2001; 20070316 (ysko)</p>
19
Gogisetty, Sai Chand. "Structural behaviour of CFRP due to impact load under hygroscopic conditions." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Find full textAbstract:
The selection of adhesively bonded composite materials to strengthen the existing concrete structures has increased due to fiber composites. The material we use in this here is Carbon Fiber Reinforced Polymer (CFRP), is an extremely strong and light fibre reinforced polymer which contains carbon fiber as primary structural component. When these materials are used in long term applications there are effects due to loads and environmental effects like effects exposed to heat, moisture etc this leads to lose of strength and stiffness causes propagation of cracks and ultimately failure. Moisture-induced ageing is recognized as one of the main causes of the long-term failure of composites.
There is a reduce in stress transfer efficiency and leads to a decrease in the mechanical properties of the composite material.
In this study we analyse how the behaviour of a carbon fiber reinforced polymer changes at impact loads (3J) at different specimen locations (central impact and near edge impact) and with no impact conditions under different hygroscopic ageing conditions (3 days and 7 days ageing). 13 specimens were used for each ageing condition in this test. The mechanical characterisation of the material is carried out through the compression tests in ENEA laboratories located in Faenza. Numerical simulations are also done using simulation software by modifying properties of the material and compared with the standard one.
20
Rafeeq, Ranj. "Torsional Strengthening of Reinforced Concrete Beams Using CFRP Composites." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/3125.
Full textAbstract:
Few decades ago, there were no guidelines for torsion design of reinforced concrete (RC) beams. Hence, many existing beams in older buildings have a lack of adequate torsional strength since they were not properly designed for torsion. One way to regain/rehabilitate adequate torsional strength is through application of externally bonded carbon fiber reinforced polymers (CFRP). To date, American Concrete Institute (ACI) code, as well as other building codes, do not have recommendations or provisions for strengthening RC beams for torsion using fiber-reinforced polymer (FRP) composites due to the inexistence of conclusive experimental and analytical data. Of the very limited works on this behavior, the majority of the focus has been devoted to experimental works. Realistic spandrel beams in a building that lack torsional strength were modelled in this research, and strengthened to examine various behaviors such as load capacity, deflection, torque, twist, crack propagation, ductility, and failure modes. For this purpose, six RC beams were tested: four reference beams and two strengthened beams were used to observe additional capacity through the use of carbon fiber-reinforced polymer (CFRP) sheets. To strengthen the beams, one layer of sheets was completely wrapped around them. Results show an additional torsional capacity of 63% and 178% relative to their respective reference beams. Through strengthening, modes of failure of the beams changed from brittle torsion-dominated failure to shear-flexure failure in both beams. The study also included crack pattern and ductility of test beams. Cracks became smaller in width and more evenly distributed across the torsion-loaded area, and torsional ductility was enhanced by 266% and 165% respectively. Flexural ductility was also greatly enhanced by more than five folds. Finally, using ACI 318-14, ACI 440.2R-02, and available formulae in the literature, the beams were analyzed and the respective values were compared.
21
Schnerch, David. "Strengthening of Steel Structures with High Modulus Carbon Fiber Reinforced Polymer (CFRP) Materials." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-06152005-090112/.
Full textAbstract:
Transportation departments and the telecommunications industry are currently demanding cost-effective rehabilitation and/or strengthening techniques for steel structures, including bridges and monopole towers. Rehabilitation is often required due to cross-section losses resulting from corrosion damage and strengthening may be required due to changes in the use of a structure. Current strengthening techniques, have several disadvantages including their cost, need to match the surface configuration of the existing structure, poor fatigue performance and the need for ongoing maintenance due to continued corrosion attack. The current research program makes use of new high modulus types of carbon fiber for strengthening steel structures. The experimental program was developed in four phases. These phases included the selection of suitable resins and adhesives for bonding the CFRP sheets and strips to the steel, characterization the bond to the steel through testing of the development length, performing large-scale tests on strengthened steel monopole towers and also determining the behavior of strengthened steel-concrete composite beams that are typical of bridge structures. The result of the experimental program was the demonstration of sizeable strength and stiffness increases for the steel structures, strengthened with the developed system. Analytical work has also been completed to predict these strength and stiffness increases as well as to determine the bond stresses to ensure the avoidance of a debonding failure, which is detrimental to the effective use of the high modulus CFRP material.
22
Badenhorst, Adriaan Jakobus. "Debonding of external CFRP plates from RC structures caused by cyclic loading effects." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20308.
Full textAbstract:
Thesis (MScEng)--Stellenbosch University, 2012.<br>ENGLISH ABSTRACT: This study set out to determine the debonding of externally applied Carbon Fibre Reinforced
Polymer (CFRP) plates from RC structures under cyclic loading. Triplet shear tests and finite
element (FE) analyses were done on the epoxy to determine the bond stress between the
CFRP plate and a reinforced concrete specimen. From these tests and analyses the
average shear strength of the bond between the epoxy and concrete substrate was
determined and the shear strength of the epoxy specified by the supplier could be confirmed.
A case study of a statically loaded beam was performed to verify the bond strength.
Finally a reinforced concrete (RC) T-section was designed and pre-cracked to simulate a
damaged beam in practice. These sections were then externally reinforced by bonding
CFRP plates onto the face of the web. The sections were subjected to static and cyclic
loading at different force amplitudes. Along with the experimental tests, FE models were
developed and analysed which had the same geometrical and material properties as the
experimental specimens. Due to time constraint a FE mesh objectivity study was not done,
but the chosen element size is believed to be sufficiently small to replicate the experimental
tests objectively.
The FE analyses and the experimental tests yielded results that were close to each other on
both the global scale and in terms of localised behaviour, thus it was decided that the
computational approach could be used for the final design of a model of the debonding of
CFRP plates bonded onto RC beams under cyclic loading because the data can be
analysed more easily and a large variation of tests can be done.
For the T-section 3 tests were conducted; a pull-off (static) test where the bonded CFRP
plate was pulled from a specimen to get the ultimate failure envelope of the test specimens.
The static test was followed by cyclic tests with force amplitude of 85% and 65% of the
ultimate pull-off strength. Different measurements were taken to get the global and local
displacement behaviour of the section. The global displacement was measured by means of
a linear variable displacement transducer (LVDT, displacement meter) clamped onto the
CFRP plate that pushed on the top of the concrete and the local displacement was
measured with the help of the Aramis system. The displacement was then compared to the
same displacements of nodes and elements in the FE models. The result was a
confirmation that the results from the FE models were sufficient to design a model for cyclic
debonding of CFRP plates from RC structures. From the FE models the relative displacement between the CFRP plate and concrete was
obtained in the vicinity of a crack. This relative displacement was then normalised by the
respective stress range of the different tests, from which the normalised relative
displacement was plotted against the number of cycles to get an equation limiting the
number of cycles for a specific stress range.
From the results, it appears that for cyclic load levels up to 65% of the peak static resistance,
a threshold number of load cycles are required for delamination initiation. Subsequently, a
near constant delamination rate is reached. The delamination rate is significantly lower for
lower cyclic load levels. Finally, an unstable delamination stage is reached at a level of
about 65 μm for all the analyses, after which CFRP pull-off is imminent.
Service life design of CFRP reinforcement of RC beams should take into consideration the
delamination initiation threshold, the subsequent delamination rate and finally the initiation of
unstable delamination.<br>AFRIKAANSE OPSOMMING: Die projek is uitgevoer om die delaminasie van ekstern aangewende Koolstof Vesel
Versterkte Polimeer (KVVP) stroke op gewapende beton strukture te bepaal onder sikliese
belasting. Triplet skuif toetse is gedoen op die gebruikte epoksie om die verband-sterkte te
bepaaltussen die KVVP stroke en die beton proefstuk. Die skuif toetse is ook met behulp
van die eindige element (EE) metode geanaliseer. Die resultaat van die toetse en analises
het gewys dat die verband sterkte tussen die KVVP stroke en beton gelyk is aan die skuif
sterkte van die epoksie wat verskaf is. `n Gevalle studie van `n monotonies belaste balk is
gedoen om die verband-sterkte te verifieër.
`n Gewapende beton T-snit is ontwerp en voor-af gekraak om `n beskadigde balk in die
praktyk voor te stel. Die beskadigde proefstukke is vervolgens ekstern versterk met KVVP
stroke wat aan die web van die T-snit vas geplak is. Die versterkte T-snitte is getoets onder
statiese en sikliese belasting. Die sikliese toetse is ook onder verskillende
spanningsamplitudes getoets. Om die eksperimentele toetse te verifieër is EE modelle
gebou en geanaliseer wat dieselfde geometriese en materiaal eienskappe as die
eksperimentele proefstukke gehad het, maar as gevolg van `n tydsbeperking is `n
sensitiwiteit studie oor die element grootte nie gedoen nie. Die element grootte is klein
genoeg gekies en word beskou as voldoende om die gedrag objektief te simuleer.
Die EE analises en eksperimentele resultate was na genoeg aan mekaar op beide globale
en lokale vlak. Dus is `n analitiese benadering tot die toetse vervolgens gebruik vir die
ontwerp van `n model vir delaminasie van KVVP stroke van gewapende beton strukture
onder sikliese belasting. Die EE metode stel die analis in staat om `n verskeidenheid van
toetse relatief vinnig uit te voer en om die data van die toetse vinniger te interpreteer as deur
fisiese eksperimentele toetse.
Drie eksperimente is uitgevoer op die T-snitte, `n aftrek-toets (staties) waar die KVVP strook
van `n proefstuk afgetrek is om die falingsomhullende diagram te kry en dan ook twee
sikliese toetse teen 85% en 65% van die krag amplitude van die falingskrag.
Verplasingsmeters is gebruik om die globale verplasing te kry, deur dit vas te klamp op die
KVVP strook en dan die verplasing te meet relatief tot die bokant van die beton. Die lokale
veplasing is met behulp van die Aramis sisteem verkry. Die eksperimentele verplasings is
dan vergelyk met verplasings van die ooreenstemmende nodes en elemente in die EE
modelle. Deur die vergelyking van die resultate is dit bevestig dat die eindige element modelle voldoende is om die model vir sikliese delaminasie van KVVP stroke van
gewapende beton strukture te gebruik vir die ontwerp.
Uit die EE modelle is die relatiewe verplasing tussen die KVVP strook en die beton gekry in
die omgewing van `n kraak. Die relatiewe verplasing is genormaliseer deur elkeen se
spanningsamplitude. Die genormaliseerde relatiewe verplasing is dan teenoor die aantal
siklusse geteken waarvan `n vergelyking vir die maksimum verplasing afgelei is om die
aantal siklusse vir `n gegewe spanning amplitude te beperk.
Uit die resultate blyk dit dat vir sikliese laste tot en met 65% van die piek statiese weerstand
`n aantal siklusse moontlik is voordat delaminasie begin waarna `n konstante delaminasie
tempo bereik word. Die delaminasie tempo is stadiger vir sikliese laste teen `n laer
belastings amplitude. Laastens word `n onstabiele delaminasie fase bereik by `n vlak van
ongeveer 65 μm, na die oorgang delamineer die KVVP strook binne enkele siklusse.
Die beginpunt van delaminasie, die delaminasie tempo en laastens die begin van onstabiele
delaminasie moet in gedagte gehou word by die ontwerp diens leeftyd van KVVP versterkte
gewapende beton balke.
23
Kabir, MD H. "Environmental durability study of CFRP strengthened steel tubular structures under four-point bending." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/91853/1/MD_Kabir_Thesis.pdf.
Full textAbstract:
This research has studied the environmental durability of CFRP strengthened steel circular hollow section (CHS) member under cold weather and a marine environment at different temperatures experimentally and numerically under bending. A significant reduction of tensile strength was found for adhesives material in both environments. The cold weather and a marine environment adversely affected the durability by reducing strength and stiffness of CFRP strengthened CHS members. An embedded GFRP layer together with CFRP layers enhanced durability in marine environment. A suitable durability design factor has been proposed under both environments.
24
Narducci, Federico. "Bio-inspired micro-structural design for CFRP : exploring damage mechanisms of nacre." Thesis, Imperial College London, 2018. http://hdl.handle.net/10044/1/60585.
Full textAbstract:
Carbon-Fibre Reinforced Polymers (CFRP) are widely regarded as the material of choice for many aerospace and automotive applications, where high specific strength and stiffness are required. However, one of the main limitations to further extending the use of such materials is their inherent brittleness, which results in the difficulty to design damage-tolerant lightweight structures. Among the innovative solutions recently proposed to improve the damage tolerance of CFRP, biomimetics provides a valuable source of inspiration. In particular, of the many biological composites, nacre is one that provides a remarkably tough behaviour, due to its discontinuous tiled micro-structure leading to damage-diffusion and crack-deflection mechanisms acting at the micro-scale. In this work, a carbon-fibre/epoxy composite with nacre-inspired tiled micro-structure is firstly designed and synthesised. Analytical and numerical models are developed to identify suitable configurations for the tile geometry with interlocks, leading to tiles of about 600 μm which are then laser-engraved in the laminate plies. In-situ bending tests show how the nacre-like interlocking micro-structure succeeds in diverting cracks and avoiding localised failure, while toughness and heterogeneity of the interface between tiles are identified as key elements to promote further spreading of damage. In order to improve the ductility of the interface, a film-casting technique is developed to deposit extremely thin layers (~13 μm) of poly(lactic acid) (PLA) onto the interface of carbon/epoxy prepregs. Different patterns of PLA texture (including fractals) are explored, with DCB and 4ENF tests showing an increase in interlaminar toughness of about 80% for Mode I and 12% for Mode II. The film-casting method mentioned above is then used to modify the interfaces of the nacre-inspired laminate, by depositing thin PLA patches with fractal shape in between plies. This results in a thin texture of thermoplastic material that toughens the interface without significantly increasing the overall thickness of the laminate. Results show that damage diffusion is considerably enhanced by the tougher and more heterogeneous interface, which succeeds in creating more extensive pull-out of the interlocking tiles. Finally, the interaction between nacre-inspired discontinuous micro-structures and continuous fibre-reinforced layers is analysed. It is shown how continuous layers can be used to trigger unstable failure in the nacre-like material, to act as a crack-propagation barrier, or to change the morphology of damage by promoting a transition from brittle failure to energy-dissipating tile pull-out.
25
Mohamamdpour, Lima Mehdi. "Experimental and Numerical Study of RC Walls with Opening Strengthened by CFRP." Thesis, Griffith University, 2016. http://hdl.handle.net/10072/367903.
Full textAbstract:
Concrete structures regularly require strengthening due to various reasons. These structures include bridges, buildings and infrastructure, across numerous sectors and industries. Based on the load-carrying capacity of structures and proposed future applications, a vast array of strengthening methods may be utilised. Due to rapid advancements in construction materials, technology has led to the achievement of being able to secure safer, more economical and functional buildings. Of the innovative materials, Fibre Reinforced Polymer (FRP) appears to be an encouraging solution for the retrofitting and strengthening of Reinforced Concrete (RC) structures because of its unique properties. These properties include: high strength-to-weight ratio; high fatigue endurance; environmental degradation and corrosion resistance. FRP is also durable and very flexible for application to the various shapes of structural members. Further, it is easy to install, with a negligible increase in structural size and weight. The application of FRP is dependent upon the type of structural member plus its behaviour. It can be used to enhance the load capacities (axial, flexural, or shear), ductility, rigidity, the remaining fatigue life as well as the durability against harsh environments.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>Griffith School of Engineering<br>Science, Environment, Engineering and Technology<br>Full Text
26
Gamino, André Luís. "Modelagem física e computacional de estruturas de concreto reforçadas com CFRP." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3144/tde-27062007-181359/.
Full textAbstract:
A proposta central desta tese é o desenvolvimento de estratégias de modelagem computacional de estruturas de concreto reforçadas com CFRP (Carbon Fiber Reinforced Polymer). Foram utilizados neste estudo os programas computacionais DIANA (plataforma comercial), QUEBRA2D e FEMOOP (plataformas acadêmicas de desenvolvimento). Em cada um dos programas foram implementados ou utilizados modelos constitutivos existentes apropriados para cada fase do sistema estrutural. Implementaram-se modelos constitutivos apropriados para o concreto, para as armaduras de aço, para os polímeros FRP e suas interfaces, a fim de representar o sistema estrutural reforçado com os compósitos. Elementos finitos de interface e de barras de treliça foram implementados (formulações discreta e incorporada) para a representação numérica das armaduras e dos compósitos, bem como de suas interfaces com o concreto. Em complementação às análises numéricas desenvolveram-se ensaios experimentais de vigas de concreto armado reforçadas com fibras de carbono - flexão e cisalhamento - de seção transversal retangular e \"T\". Esses ensaios, assim como outros disponíveis na literatura, são essenciais para uma melhor interpretação sobre a eficiência do reforço e também para a validação da capacidade de modelagem numérica desenvolvida. Foram avaliadas as eficiências dos sistemas de compósitos de fibra de carbono aplicados em reforços de vigas submetidas à flexão e ao cisalhamento, bem como os seus mecanismos de colapso mediante a aplicação de carregamentos monotônicos. Complementarmente, efetuaram-se análises comparativas com os modelos de dimensionamento sugeridos por diferentes normas técnicas ou disponíveis na literatura técnica.<br>The purpose of this thesis is the development of strategies for computational modeling of reinforced concrete structures strengthened with CFRP (Carbon Fiber Reinforced Polymer). The software systems DIANA (commercial system), QUEBRA2D and FEMOOP (academic systems) have been utilized. In each program appropriate constitutive models have been implemented or existing ones used for representing each phase of the structural system. Appropriate constitutive models for concrete, rebars, CFRP reinforcement and bond-slip interfaces have been implemented and adjusted to represent the behavior of the composite system. Interface and truss finite elements have been implemented (discrete and embedded approaches) to represent rebars and CFRP\'s, as well their interfaces with concrete. An experimental study of reinforced concrete beams with rectangular and \"T\" cross sections strengthened with CFRP - under bending and shear - have been realized to complement the numerical study. These tests, as well as others available in the literature, are very useful for a better understanding of the strengthening capacity of the CFRP\'s and also for the validation of the proposed computational modeling. The efficiency of CFRP systems for bending and shear strengthening has been evaluated, as well as the collapse mechanisms observed under monotonic loads. In addition comparative analyses with design models prescribed by different codes of practice and others proposed in the literature have been carried out.
27
Ryan, Shannon, and shannon ryan@studentems rmit edu au. "Hypervelocity Impact Induced Disturbances on Composite Sandwich Panel Spacecraft Structures." RMIT University. Aerospace, Mechanical & Manufacturing Engineering, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080808.092240.
Full textAbstract:
The next generation of European scientific satellites will carry extremely sensitive measurement devices that require platform stability orders of magnitude higher than current missions. It is considered that the meteoroid and space debris (M/SD) environment poses a risk to the success of these missions as disturbances induced by the impact of these particles at hypervelocity may degrade the platform stability below operational requirements. In this thesis, disturbances induced by the impact of M/SD particles at hypervelocity on a representative scientific satellite platform have been investigated. An extensive experimental impact test program has been performed, from which an empirical ballistic limit equation (BLE) which defines the conditions of structural perforation for composite sandwich panel structures with CFRP facesheets and aluminium honeycomb cores (CFRP/Al HC SP) has been defined. The BLE is used to predict impact conditions capable of inducing the different excitation modes relevant for a SP sandwich panel structure, enabling a significant reduction in the time and expense usually required for calibrating the protective capability of a new structural configuration. As experimental acceleration facilities are unable to cover the complete range of possible in-orbit impact conditions relevant for M/SD impact risk assessment, a Hydrocode model of the representative CFRP/Al HC SP has been constructed. A series of impact simulations have been performed during which the local impact-induced disturbance has been measured. The numerical disturbance signals have been validated via comparison with experimental disturbance measurements, and subsequently subject to a characterisation campaign to define the local elastic excitation of the SP structure equivalent to that induced by impact of a M/SD particle at hypervelocity. The disturbance characterisation is made such that it is applicable as an excitation force on a global satellite Finite Element (FE) model, allowing propagation of impact-induced disturbances throughout the complete satellite body to regions of critical stability (i.e. measurement devices). The disturbance induced upon measurement devices by M/SD impacts at both near- and far-body locations can then be made, allowing the threat to mission objectives to be assessed.
28
Squires, Charlene. "Development of CFRP Class A body panels and structural components for automotive applications." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/68692/.
Full textAbstract:
Investigations were completed in two areas of research. Firstly mechanical compression test coupons of unidirectional carbon fibre composite were optimised to produce repeatable and reproducible data to support automotive structural applications. The compressive strength was determined through ASTM D 695 M testing, and the results were correlated with test variations implemented. Various preparation methods were evaluated in the determination of the cause of variation found in unidirectional carbon fibre test specimens. Analytical tools were implemented, including microscopical techniques, Scanning Electron Microscope, Talyscan and X-Ray Tomography to determine initiation of failure and to quantify the damage encountered by the compressive test specimen. The findings correlated well with the mechanical test results, which indicate that the higher quality laminates in terms of surface and edge finishes will have better mechanical properties compared to lower quality composites. Secondly, the characterisation of the surface of a material designed for automotive body applications. The CBS 95 is manufactured by Gurit UK and has been designed to be the first carbon fibre material to be cured using vacuum bagging and have no evidence of print through at the surface. Various characterisation tools, including Proscan 2000, microscopical techniques, and Dynamic Mechanical Analysis, were used to evaluate anomalies found at the surface of the components manufactured from CBS 95. The origin and formation mechanisms of the anomalies was sought and explained with use of models and the analytical equipment, two main origins were found: porosity and kitting defects. Additionally, the sustainability of CBS 95 exposed to harsh environments was investigated. The CBS 95 was exposed for 20 weeks in three different environments (hot/dry, hot/wet and chemical). Analytical techniques such as MINOLTA Spectrophotometer CM-500 Series, Gloss analyser and microscopical techniques were used to quantify the environmental degradation of the CBS 95. The CBS 95 performed consistently in each of the three environments. The work has also made many recommendations for improved manufacturing routes for both the compressive test specimen and the CBS 95, reducing processing time and improving quality. These suggestions, when considered together, contribute significantly to carbon fibre manufacturing.
29
Le, Duy Tan. "Structural Response of Precast Segmental Concrete Beams Prestressed with Unbonded Steel/CFRP tendons." Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/79286.
Full textAbstract:
This study investigates the use of Carbon fibre-reinforced polymer (CFRP) tendons on precast segmental concrete bridge beams (PSBs). Experimental and numerical results have approved the feasibility of applying CFRP tendons on this type of structure in construction practice for corrosion control that allows to reduce lifecycle maintenance costs of the structure. A new analytical procedure for predicting deflections and closed-form equations to estimate the balanced reinforcement ratio of PSBs with unbonded tendons are also developed.
30
Cassino, Christopher Daniel. "Detection of fiber fracture in Unidirectional Fiber Reinforced Composites using an In-Plane Fiber Optic Sensor." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/32419.
Full textAbstract:
Fiber reinforced polymers (FRP) are an efficient and inexpensive method of repairing deteriorating infrastructure. FRP sheets can be applied to spalling bridge sections and columns to prevent further deterioration and increase stiffness. However, the effect of the environment on the long-term durability of FRP and how the various damage mechanisms initiate and develop are not known. Systems for structural health monitoring are being sought as a means of managing important components in transportation systems as assets in light of modern life cycle cost concepts. This study characterizes a fiber optic sensor for use in detecting acoustic emissions (AE) in FRP. The results of AE analysis (signal amplitude, frequency spectra, MARSE, and in-plane displacement) caused by simulated fiber fracture experiments and other types of mechanical loading in FRP test coupons are reported. The applications to the development of FRP structural health monitoring systems are also discussed.<br>Master of Science
31
Lanzoni, Maicol. "Applicazione di reticoli di Bragg "chirped" per il monitoraggio strutturale di laminati CFRP." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8512/.
Full textAbstract:
L’uso dei materiali compositi è andato aumentando negli ultimi decenni per la loro elevata rigidezza, la resistenza specifica e il possibile risparmio, notevole in termini di peso dell’intera struttura.
Tali materiali introducono però nuove problematiche riguardanti le modalità di danneggiamento e il comportamento a fatica. Mentre questi fenomeni sono relativamente ben compresi nei materiali metallici, per una struttura in composito non esistono ancora modelli in grado di predire con sufficiente affidabilità l’evoluzione del danneggiamento.
Negli ultimi anni la ricerca si è focalizzata sullo sviluppo di sistemi in grado di rilevare la presenza e l’evoluzione del danno, definiti Structural Health Monitoring Systems, ovvero sistemi di monitoraggio strutturale.
Il danneggiamento strutturale può così essere individuato e identificato per mezzo di sensori distribuiti integrati nella struttura stessa, aventi la possibilità di trasmettere queste informazioni a un sistema di analisi esterno permettendo di valutare lo stato di degrado della struttura in tempo reale.
In questo contesto si inseriscono le attività di ricerca sulle strutture intelligenti che, inglobando al loro interno opportune tipologie di sensori e attuatori, sono in grado di monitorare l’ambiente fisico operativo, raccoglierne e interpretarne le informazioni per poi rispondere ai cambiamenti della struttura in modo appropriato attraverso gli attuatori.
L’impiego di sensori e attuatori inglobati nelle strutture offre molteplici vantaggi rispetto ai sistemi di trasduzione e attuazione convenzionali.
L’attività di ricerca condotta in questa tesi è rivolta all’indagine di tecniche di SHM per mezzo di sensori a fibra ottica. Essi presentano molteplici peculiarità che li rendono i candidati ideali per queste applicazioni.
Esistono diversi tipi di sensori che utilizzano le fibre ottiche. Nel presente lavoro si sono utilizzati sensori di deformazione basati sui reticoli di Bragg (FBG) chirped. Questi sensori sono costituiti da un reticolo inscritto all’interno della fibra, che ha l’effetto di riflettere solo alcune lunghezze d’onda della luce incidente. Se le proprietà geometriche del reticolo cambiano per effetto di una deformazione, cambia anche la forma dello spettro riflesso. Inoltre, con il tipo di sensore usato, è possibile correlare lo spettro con la posizione di eventuali danneggiamenti interni al materiale.
Gli obbiettivi di questa ricerca sono di verificare gli effetti della presenza di una fibra ottica sulle caratteristiche meccaniche di un laminato e di trovare un legame tra la risposta in frequenza del sensore FBG e lo stato tensionale e il grado di danneggiamento di un componente in composito.
32
Oliveira, Clayton Reis de. "Sistemas de proteção para concreto reforçado com CFRP em situação de incêndio." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258466.
Full textAbstract:
Orientador: Armando Lopes Moreno Junior<br>Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo<br>Made available in DSpace on 2018-08-20T12:44:06Z (GMT). No. of bitstreams: 1
Oliveira_ClaytonReisde_D.pdf: 8877102 bytes, checksum: d8520eb5d1f0d3af309830281acd7dfc (MD5)
Previous issue date: 2012<br>Resumo: A técnica de polímeros reforçados com fibras (FRP) vem sendo cada vez mais utilizada como alternativa de reforço estrutural, com o objetivo de aumentar a resistência e a ductilidade das estruturas de concreto armado. Entretanto, o desempenho desses sistemas em situação de incêndio é uma séria preocupação devido ao fato dos materiais de FRPs serem combustíveis. Informações a esse respeito ainda estão restritas à literatura internacional e, mesmo assim, ainda são escassas e limitadas. Assim, antes de serem utilizados, com segurança, em reforços estruturais no interior de edifícios, os FRPs devem ter seu comportamento avaliado em situação de incêndio, verificando tanto o cumprimento dos critérios de resistência ao fogo, especificados em códigos normativos nacionais, quanto procedimentos de dimensionamento dessas estruturas contra a ação do fogo. Este trabalho, inicialmente, reuniu informações disponíveis na literatura internacional sobre os principais efeitos da exposição à altas temperaturas de cada material componente do compósito e, na mesma linha, sobre o comportamento de elementos estruturais reforçados com fibra de carbono em situação de incêndio. A parte experimental do trabalho consistiu na avaliação em laboratório do comportamento de corpos de prova de concreto reforçados com fibra de carbono. As variáveis em análise foram a temperatura limite de exposição do reforço e o tipo de revestimento de proteção ao fogo desses elementos reforçados. Os resultados mostraram que o reforço perde sua eficiência já nos primeiros minutos de exposição ao fogo e que os materiais de proteção, usuais na proteção de elementos de aço, são ineficazes em manter a segurança do sistema FRP em situação de incêndio. Uma simulação computacional via Elementos Finitos, utilizando o software TCD foi feita. Ao final, os resultados deste trabalho confirmaram procedimentos normativos internacionais vigentes que, por unanimidade, enfatizam que durante o incêndio a resistência proporcionada pelo reforço de compósito FRP deve ser desprezada<br>Abstract: The fiber technique reinforced polymer (FRP) has been used as alternative of structural reinforcement, with the objective to increase the resistance and ductilidade of the reinforcement concrete structures. However, the performance of these systems in fire situation is a serious concern due to the fact of the FRP materials to be combustible. Information to this respect still remain restricted to international literature and, eventhose, still scarced and limited. Thus, before being used, with safety, in structural reinforcements in the interior of buildings, the FRPs must have its behaviour evaluated in fire situation. This paper analyzed the main effects of exposure to high temperatures in FRP systems and investigated this material at laboratory. The main parameter evaluated were the critical temperature of fire exposed and the type of fire coating. The results showed that the reinforcement has lost its efficacy in the first minutes of exposure to fire and protection materials evaluated were ineffective in maintaining the security of the system under fire. Using the software TCD, a computer simulation was generated. At the end, the study confirmed that current code procedures unanimously emphasize: the additional resistance provided by the FRP can not be considered on fire safety design concrete structures<br>Doutorado<br>Estruturas<br>Doutor em Engenharia Civil
33
Batuwitage, Chamila Rajeev Jayanath. "Evaluation of environmental durability and bond characteristics of carbon fibre reinforced polymer (CFRP) strengthened steel structures." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/106775/1/Chamila%20Rajeev%20Jayanath_Batuwitage_Thesis.pdf.
Full textAbstract:
This thesis evaluates the environmental durability and bond characteristics of carbon fibre reinforced polymer (CFRP)-strengthened steel structures. The findings of this research provide a valuable contribution to the knowledge of CFRP-steel strengthening systems which can be used to evaluate the durability performance of CFRP-steel strengthening systems. Various parameters which related to the durability of CFRP-steel strengthening systems were investigated and evaluated. The outcomes of this research will be beneficial to the structural engineers when designing and assessing CFRP-steel systems.
34
Smith, Jeffrey L. "LIFE-CYCLE COST ANALYSIS OF REINFORCED CONCRETE BRIDGES REHABILITATED WITH CFRP." UKnowledge, 2015. http://uknowledge.uky.edu/ce_etds/33.
Full textAbstract:
The deterioration of highway bridges and structures and the cost of repairing, rehabilitating, or replacing deteriorated structures is a major issue for bridge owners. An aging infrastructure as well as the need to upgrade structural capacity for heavier trucks adds to problem. Life-cycle cost analysis (LCCA) is a useful tool for determining when the deployment of fiber-reinforced polymer (FRP) composite components is an economically viable alternative for rehabilitating deteriorated concrete bridges.
The use of LCCA in bridge design and rehabilitation has been limited. The use of LCCA for bridges on a project level basis has often been limited to the non-routine design of major bridges where the life-cycle cost model is customized.
LCCA has historically been deterministic. The deterministic analysis uses discrete values for inputs and is fairly simple and easy to do. It does not give any indication of risk, i.e. the probability that the input values used in the analysis and the resulting life-cycle cost will actually occur.
Probabilistic analysis accounts for uncertainty and variability in input variables. It requires more effort than a deterministic analysis because probability distribution functions are required, random sampling is used, and a large number of iterations of the life-cycle cost calculations are carried out. The data needed is often not available.
The significance of this study lies in its identification of the parameters that had the most influence on life-cycle costs of concrete bridge and how those parameters interacted. The parameters are: (1) Time to construct the new bridge; (2) traffic volume under bridge (when applicable); (3) value of time for cars; and (4) delay time under the bridge during new bridge construction (when applicable). Using these parameters the analyst can now “simulate” a probabilistic analysis by using the deterministic approach and reducing the number of iterations. This study also extended the use of LCCA to bridge rehabilitations and to bridges with low traffic volumes. A large number of bridges in the United States have low traffic volumes. For the highway bridge considered in the parametric study, rehabilitation using FRP had a lower life-cycle cost when compared to the new bridge alternative.
35
Al-Obaidi, Salam. "Behavior of Reinforced Concrete Beams Retrofitted in Flexure Using CFRP-NSM Technique." PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2294.
Full textAbstract:
A variety of retrofitting methods are used to upgrade existing structures. For example, steel plates and Fiber Reinforced Polymer (FRP) jackets are externally bonded to members to increase their capacity in flexure and shear. However, due to the issue of corrosion these strengthening systems may lose their efficiency with time. FRP materials have been used to strengthen many structural components of different shapes and types. FRP jackets, FRP Strips, and FRP rods have commonly been used to rehabilitate existing structural components. The many advantages of using FRP as strengthening materials have made this material an attractive alternative: advantages such as lightweight, high strength, and ease of setting up. Among the many applications using FRP, Near Surface Mounted -- Fiber Reinforced polymer (NSM-FRP) is a promising technique used to strengthen concrete members. However, de-bonding issues have to be overcome to make this technique efficient and reliable. The NSM-FRP technique consists of making a groove along the surface of the concrete member to be retrofitted with depth less than the cover of the member. After cleaning the groove, epoxy paste is used to fill two-thirds of the groove's depth. The FRP element is then mounted in the groove. Finally, the groove is filled with epoxy and the excessive epoxy is leveled with surface of the concrete. This technique makes the FRP material completely covered by epoxy in the cover of the concrete. This method can be used for strengthening both the positive and negative moment regions of girders and slabs. Groove size, paste, concrete, and rods properties are the main variables that control the efficiency of the NSM-FRP rods. The main objective of this research project is to determine the behavior of reinforced concrete beams that are strengthened with NSM-CFRP reinforcement bars. In this research project, the bond characteristics of NSM-CFRP reinforcement bars are first determined from pullout tests. Then, NSM-CFRP rods are installed in reinforced concrete beams and the beams are tested. Loads, strains, and deflections are measured and theoretical and measured capacities are compared. Finally, the reliability and efficiency of using NSM-CFRP rods technique in retrofitting existing structures is observed.
36
Akin, Emre. "Strengthening Of Brick Infilled Rc Frames With Cfrp Reinforcement-general Principles." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613172/index.pdf.
Full textAbstract:
There is an excessive demand for the rehabilitation of frame type reinforced concrete (RC) buildings which do not satisfy current earthquake code provisions. Therefore, it is imperative to develop user-friendly seismic strengthening methodologies which do not necessitate the evacuation of building during rehabilitation period.
In this study, it was aimed to strengthen the brick infill walls by means of diagonal Carbon Fiber-Reinforced Polymer (CFRP) fabrics and to integrate them with the existing structural frame in order to form a new lateral load resisting system. The possible effects of height to width (aspect) ratio of the infill walls and scale of the frame test specimens on the overall behavior attained by the developed rehabilitation methodology were investigated.
The experimental part of the study was carried out in two steps. In the first step, ten individual panel specimens were tested in order to understand the behavior of strengthened/non-strengthened masonry walls under diagonal earthquake loads. And in the second step, the tests of eight 1/3 and four 1/2 scaled one-bay, two-story RC frames having two different aspect ratios were performed to determine design details. The experimental results were revealed in terms of lateral stiffness, strength, drift and energy dissipation characteristics of the specimens.
In the analytical part, an equivalent strut and tie approach was used for modeling the strengthened/non-strengthened infill walls of the frames. The predicted pushover responses of the frame models were compared with the test results. The design criteria required for the aforementioned strengthening methodology was developed referring these analytical results.
37
Harder, Sergej [Verfasser]. "Near-infrared laser surface treatment of milled CFRP aircraft structures for bonded repair applications / Sergej Harder." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2020. http://d-nb.info/1222589230/34.
Full text
38
Mohammed, Bizuayehu Y. "Damage characterisation in twill-weave CFRP composite aircraft structures using modal analysis of acoustic emission signals." Thesis, University of South Wales, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.702330.
Full textAbstract:
The aim of this research work is to propose a damage characterisation method using acoustic emission technology. The research is broadly categorised in structural health monitoring (SHM) of CFRP composite structures. A number of tests were performed on twill-weave CFRP composite material in correlating the various damage types to their associated signal features. Recent developments in aircraft structural material lead to an increase use of CFRP composite structures. However, these materials are susceptible to different modes of failures such as matrix cracking, delamination, stringer debonding, and fibre fracture which affect the integrity of the structure. Determining the type of failure during service life of an aircraft structure is an important input in the SHM of materials. This can potentially reduce inspection time, and increases knowledge of the damage type propagating within the said structure. Acoustic emission (AE) is a phenomenon where a stress wave is generated due to stresses in a material. AE sensors can be placed on the surface of the structure to detect these waves while the material is in service. These waves have possess distinct signal features which can be attributed to a particular damage type. Therefore, AE based technology is potentially suitable for the SHM of composite structures. This thesis proposes an improved damage characterisation method for twill weave CFRP composite when subjected to various modes of failure. These failure modes were achieved using a variety of test setups namely cantilever bending, three point bending, stringer debonding, and tensile testing. The proposed method uses live digital microscope video recording of events along with AE events. Distinct signal features were identified for delamination initiation and propagation, matrix cracking, fibre fracture and skin-stringer debonding.
39
Argelli, Michael. "Monitoraggio strutturale (structural health monitoring) di laminati CFRP tramite reticoli di Bragg in fibra ottica." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/6729/.
Full textAbstract:
Lo studio si propone di valutare la capacità dei reticoli di Bragg in fibra ottica, di individuare e monitorare danneggiamenti presenti all'interno di laminati in composito, tramite l'analisi degli spettri riflessi dai reticoli stessi. Sono stati utilizzati due tipi diversi di stratificazione dei laminati, per valutare il diverso comportamento dei reticoli di Bragg inseriti all'interno dei laminati.
Le proprietà dei materiali e degli spettri riflessi dai reticoli, sono state messe in relazione qualitativamente e quantitativamente, al fine di sviluppare un valido metodo di Structural Health Monitoring.
40
Darvell, Magnus. "Randomized CFRTP tape piece laminates in structural automotive applications." Thesis, KTH, Lättkonstruktioner, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185019.
Full textAbstract:
The automotive industry is facing big challenges in meeting the future environmental demands. To be able to meet these demands reduced vehicle weight is an important part. A thorough investigation was made to better get an idea of which demands the automotive industry makes in the question of lightweight materials and how far they have come in the matter. This thesis work has been performed on behalf of Oxeon AB to investigate the future for carbon fiber thermoplastics in big scale production of structural details in the automotive industry. And also to see how the material can be improved and make implementation easier by changing the materials good properties in one direction to equal and good properties in two dimensions. This is made by randomly spreading small and thin tape pieces made from carbon fiber reinforced thermoplastics to form an "organo sheet". The idea is that Oxeon AB shall make these "organo sheets" and then forward them to the automotive industry for pressing to final parts by adding heat and pressure. The most important part for this thesis work was to develop a method to spread out the pieces of carbon fiber reinforced thermoplastic tape to get a material with good two dimensional properties. Different methods to achieve this were carried out and the results were then compared with simulations for randomized tape pieces. The randomized tape pieces were then consolidated in a belt press to form an "organo sheet" and then plate pressed to form a material that simulated the end product, this to enable further evaluation of the mechanical properties. The results of both tests and simulations show that the randomization doesn’t solve the problem entirely because there will remain a slight difference between the two dimensions. The results of mechanical tests that were carried out shows that the plate pressed material have good prospects but enhancements are to be needed.<br>Fordonsindustrin står inför stora utmaningar för att möta framtida miljökrav. För att nå dessa så är minskad fordonsvikt en viktig del. En grundlig undersökning gjordes därför för att få en bättre uppfattning om vilka krav fordonsindustrin ställer på dessa lättviktsmaterial och hur långt de kommit i frågan. Det här examensarbetet har utförts på uppdrag av Oxeon AB för att undersöka framtiden för kolfiberarmerad termoplast för storskalig produktion av strukturella detaljer inom fordonsindustrin. Samt att se hur detta materials förutsättningar kan förenklas/förbättras genom att omvandla materialets goda endimensionella egenskaper till så bra tvådimensionella egenskaper som möjligt. Detta genom att slumpmässigt fördela små tunna tejpbitar av termoplastarmerad kolfiber över en yta för att bilda ett så kallat "organo sheet". Tanken är att Oxeon AB ska tillverka detta "organo sheet" och därefter skicka detta vidare till fordonsindustrin som pressar "organo sheetet" till önskad detalj genom att tillföra värme och tryck. För det här projektet var den viktigare delen att ta fram en metod för att sprida de tunna kolfiberarmerade bitarna över en yta för att åstadkomma ett material med goda egenskaper i två dimensioner. Olika metoder för detta testades och resultaten jämfördes med simuleringar för slumpmässigt fördelade tunna bitar. De randomiserade tejpbitarna konsoliderades sedan i en bandpress till ett "organo sheet och plattpressades sedan för att tillverka ett material som ska likna slutprodukten för vidare utvärdering av mekaniska egenskaper. Resultatet utifrån tester och simuleringar visade att slumpmässighet av tejpbitar inte löser problemet helt och hållet eftersom en viss skillnad av egenskaperna i de två dimensionerna kommer att kvarstå. Resultat av mekaniska prover som utförts visar att det plattpressade materalet har goda förutsättningar men förbättringar kommer att krävas.
41
Jawdhari, Akram Rasheed. "BEHAVIOR OF RC BEAMS STRENGTHENED IN FLEXURE WITH SPLICED CFRP ROD PANELS." UKnowledge, 2016. http://uknowledge.uky.edu/ce_etds/37.
Full textAbstract:
FRP laminates and fabrics, used as an externally bonded reinforcement (EBR) to strengthen or repair concrete members, have proven to be an economical retrofitting method. However, when used to strengthen long-span members or members with limited access, the labor and equipment demands may negate the benefits of using continuous EBR FRP. Recently, CFRP rod panels (CRPs) have been developed and deployed to overcome the aforementioned limitations. Each CRP is made of several small diameter CFRP rods placed at discrete spacing. To fulfill the strengthening length, CRP’s are spliced together and made continuous by means of overlaps (or finger joints).
In this doctoral dissertation, the effectiveness of spliced CRPs as flexural strengthening reinforcement for RC members was investigated by experimental, analytical and numerical methods. The experimental research includes laboratory tests on (1) RC beams under four-point bending and (2) double-lap shear concrete specimens. The first set of tests examines the behavior of concrete members strengthened with spliced CRPs. Several beams were fabricated and tested, including: (a) unstrengthened, (b) strengthened with spliced CRPs, (c) strengthened with full-length CRPs, and (d) strengthened with full-length and spliced CFRP laminates. The double-lap shear tests serve to characterize the development length and bond strength of two commonly used CRPs. Several small-scale CRPs, with variable bond lengths, were tested to arrive to an accurate estimation of development length and bond strength. Several other specimens were additionally tested to preliminarily examine the effects of bond width and rod spacing.
A 3D nonlinear finite element simulation was utilized to further study the response of CRP strengthened RC beams, by extracting essential data, that couldn’t be measured in the experimental tests. Additionally, analytical tools were added to investigate the behavior of tested bond and beam specimens. The first tool complements the double-lap shear tests, and provides mathematical terms for important characteristics of the CRP/concrete bond interface. The second tool investigates concrete cover separation failure, which was observed in the beam testing, for RC beams strengthened with full-length and spliced CRPs.
42
Matt, Howard M. "Structural diagnostics of CFRP composite aircraft components by ultrasonic guided waves and built-in piezoelectric transducers." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3238426.
Full textAbstract:
Thesis (Ph. D.)--University of California, San Diego, 2007.<br>Title from first page of PDF file (viewed January 4, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 203-216).
43
Tostain, Floran. "Apports de l'analyse comparée des processus de fragmentation et de création de débris dans la compréhension du comportement à l'écrasement de structures composites aéronautiques." Thesis, Toulouse, ISAE, 2016. http://www.theses.fr/2016ESAE0034/document.
Full textAbstract:
La certification des aéronefs au crash ou à l’atterrissage dur nécessite de concevoir et dimensionner des structureslégères vérifiant les exigences d’absorption d’énergie. Le critère de performance est l’énergie d’absorptionspécifique (Specific Energy Absorption, SEA). Nos travaux expérimentaux et numériques visent une meilleurecompréhension de la contribution favorable ou défavorable des modes de ruine à la stabilité et à l’amplitude del’énergie consommée. Le travail expérimental, réalisé sur des échantillons plaques stratifiées en T700/M21 faible grammage et interlock 55% ou 100%, compare les niveaux et les évolutions des forces d’écrasement avec l’apparition et le maintien desmodes de ruine majeurs que sont l’évasement, les fragmentations en coeur de plis et localisée en bout de pli.L’observation et la mesure des processus dynamiques de fragmentation représentent un verrou contourné ici parune analyse point à point de la synchronisation entre les films des essais et les courbes force-déplacement, et parl’observation post-mortem des échantillons, des débris et des fragments. Les plaques ont une performance àl’écrasement sensible à l’épaisseur des plis et aux vitesses de déformation. Pour les interlocks, c’est le sens detissage qui a le plus d’effet sur l’amplitude et la stabilité de la SEA, et génère un évasement global plus instable.La simulation numérique dynamique transitoire non-linéaire est utilisée comme outil complémentaire de mesureet d’analyse des essais sur plaques T700/M21 [0°/90°]. La morphologie d’écrasement est bien reproduite.L’analyse des processus de ruine à l’échelle du pli fait apparaître l’interaction entre la résistance mécanique encompression transverse du matériau (Yc) et la résistance à la déchirure en cisaillement de la structure (GIIc), etl’articulation et/ou la compétition entre évasement et fragmentation en cœur de pli qui en découlent. La mesurede la contribution des trois modes de ruine dans l’énergie consommée effectuée au travers de l’évolution desseuils de ruine permet de suivre l’évolution correspondante de l’effort d’écrasement. Une étude a été menée surla robustesse du modèle, et permet d’évaluer plus généralement la sensibilité en amplitude et en stabilité de laSEA aux propriétés de résistance mécanique identifiées comme influentes<br>The certification of aircrafts to hard landing or crash situations needs to design lightweight structures meetingrequirements in term of energy absorption. The Specific Energy Absorption (SEA) is used to compare theperformance of different structures. Experimental and numerical studies led in our work aim to improve theunderstanding of the influence of ruin modes on the crushing stability and the energy absorption capacity.Crushing experimental tests are carried on low-weight T700/M21 CFRP laminated plates and on 55% or 100%Interlock configurations. The crushing force value and its variations are compared to the proportion of inside plyfragmentation, localized fragmentation and splaying mode observed during the crushing process. The observationand the measure of the dynamic process of fragmentation are lock problems circumvented by two means. First, astep by step observation of synchronized tests’ pictures and force-displacement points is conducted. Second, apost-mortem observation of the specimen and a collect of debris and fragments is carried out. It is shown thatcomposite laminates behaviour is influenced by the ply thickness and the strain-rate parameters. For the Interlock,the woven directions have the most important effect on the SEA value and stability and can produce a globalfragmented splaying with some instability. Nonlinear transient dynamic numerical simulations are used as an additional tool to measure and analyse the experimental tests on T700/M21 [0°/90°] plates. The crushing morphology is correctly reproduced. The analysis of damage at the mesoscale shows the interaction between the mechanical transverse compressive strength of thematerial (Yc) and the shear strength of interfaces between plies (GIIc), and the link and/or the competition betweensplaying and inside ply fragmentation. The measure of the contribution of the three ruin modes in the dissipatedenergy is performed and linked to the variations of the crushing force. A study is carried out on the robustness ofthe model and allows linking the SEA value and stability to the mechanical strength properties identified asinfluential parameters
44
Stanford, Kirk Alan. "STRENGTHENING OF STEEL STRUCTURES WITH HIGH MODULUS CARBON FIBER REINFORCED POLYMERS (CFRP) MATERIALS: BOND AND DEVELOPMENT LENGTH STUDY." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-12202008-112409/.
Full textAbstract:
Cost-effective solutions for the rehabilitation and strengthening of steel structures, such as steel bridges and steel monopole towers used for cellular phone antennas, are greatly needed by government transportation departments and industry. Rehabilitation is often required due to loss of cross-section from corrosion and/or changes of the demand or use of a structure. Current techniques for strengthening steel structures have several drawbacks including requiring heavy equipment for installation, their fatigue performance, in addition to the need for ongoing maintenance due to continued corrosion attack. The current research program proposed the use of a new high modulus carbon fiber reinforced polymer (CFRP) for strengthening of steel structures. This program includes extensive research to select the resin for wet lay-up of carbon fiber sheets and the adhesives for bonding of pre-cured laminate strips. The bond behavior of FRP materials to steel structures is quite different from that of concrete structures. Preliminary test results showed the occurrence of very high bond stresses for most strengthening applications due to the amount of strengthening required for developing the material for steel structures and bridges.
45
Kaiser, Richard Lawrence. "Analysis and Connection of Lightweight CFRP Sandwich Panels for Use as Floor Diaphragms in Structural Steel Buildings." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/321006.
Full textAbstract:
A lightweight carbon fiber reinforced polymer (CFRP) sandwich panel has been developed for floor use in commercial office building construction. CFRP laminate skins were combined with low-density rigid polyurethane foam to create a composite sandwich panel suitable for floor use. The CFRP sandwich panel was optimized to withstand code prescribed office-building live loads using a 3D finite element computer program called SolidWorks. The thickness of the polyurethane foam was optimized to meet both strength and serviceability requirements for gravity loading. Deflection ultimately was the controlling factor in the design, as the stresses in the composite materials remained relatively low. The CFRP sandwich panel was then subjected to combined gravity and lateral loading, which included seismic loads from a fictitious 5-story office building located in a region of high seismic risk. The results showed that CFRP sandwich panels are a viable option for use with floors, possessing sufficient strength and stiffness for meeting code prescribed design loads, while providing significant benefits over traditional construction materials.
46
Erdogan, Hakan. "Improvement Of Punching Strength Of Flat Plates By Using Carbon Fiber Reinforced Polymer (cfrp) Dowels." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612728/index.pdf.
Full textAbstract:
Due to their practical application, flat-plates have been commonly used slab type in constructions in recent years. According to the investigations that were performed since the beginning of the 20th century, the vicinity of the slab-column connection is found to be susceptible to punching failure that causes serious unrepairable damage leading to the collapse of the structures. The objective of this study is to enhance the punching shear strength of slab-column connections in existing deficient flat plate structures. For this purpose, an economical and easy to install strengthening method was applied to ¾<br>scale flat-slab test specimens. The proposed strengthening scheme employs the use of in house-fabricated Carbon Fiber Reinforced Polymer (CFRP) dowels placed around the column stubs in different numbers and arrangements as vertical shear reinforcement. In addition, the effect of column aspect ratio on strengthening method was also investigated in the scope of this study. Strength increase of at least 30% was obtained for the CFRP retrofitted specimens compared to the companion reference specimen. Three-dimensional finite element analyses of test specimens were conducted by using the general purpose finite element analyses program. 3-D finite element models are successful in providing reasonable estimates of load-deformation behavior and strains. The experimental punching shear capacities and observed failure modes of the specimens were compared with the estimations of strength and failure modes given by punching shear strength provisions of ACI 318-08, Eurocode-2, BS8110-97 and TS500. Necessary modifications were proposed for the existing provisions of punching shear capacity in order to design CFRP upgrading.
47
Carswell, Casey. "The Structural Characterization of Two Prokaryotic Membrane Proteins: CfrA and ELIC." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31214.
Full textAbstract:
This thesis focuses on the structural and functional characterization of two integral membrane proteins; CfrA, an outer membrane TonB-dependent transporter (TBDT) from Campylobacter jejuni, and ELIC, a pentameric ligand-gated ion channel (pLGIC) from Erwinia Chrysanthemi. The spectroscopic characterization of CfrA revealed a fold consistent with the structural and biophysical properties observed for other TBDT. Both a homology model of CfrA and sequence alignments of CfrA with other ferric-enterobactin transporters suggested a unique mode of ligand binding, thus raising the possibility that C. jejuni can be specifically inhibited. To investigate the molecular determinates of binding to CfrA, I set out to crystallize CfrA. Hundreds of crystal trials led to crystals diffracting to 3.6 Å resolution, with a complete data set acquired at 5 Å resolution that led to a structural model of the CfrA β-barrel.
In the second part of this thesis, I reconstituted ELIC into model membranes in order to test the role of intramembrane aromatic interactions in ELIC gating and lipid sensing. ELIC was reconstituted into both asolectin (aso-ELIC) and 1-palmitoyl-2-oleoyl phosphatidylcholine (PC-ELIC), membranes that stabilize the homologous nicotinic acetylcholine receptor (nAChR) in functional coupled versus non-functional uncoupled conformations, respectively. In both membrane environments, ELIC exhibits a mixed α-helical and β-sheet secondary structure, with a thermal denaturation intermediate between those of the nAChR and the close prokaryotic homolog, GLIC, in similar membranes. The data suggest that although ELIC has a decreased propensity to adopt an uncoupled conformation relative to the nAChR, its ability to undergo cysteamine-induced channel gating is sensitive to its lipid environment. The decreased propensity to uncouple may reflect an increased level of aromatics at the interface between the transmembrane α-helices, M1, M3, and M4. To test this hypothesis further, the level or aromatic residues at the M1, M3, and M4 interface in both GLIC and ELIC were varied, and in both cases the levels of intramembrane aromatic interactions correlated with the efficiency of coupling binding to gating. The data provide further evidence for a role of intramembrane aromatics in channel gating and in dictating the propensity of pentameric ligand-gated ion channels to adopt an uncoupled conformation.
48
Maluk, Cristian. "Development and application of a novel test method for studying the fire behaviour of CFRP prestressed concrete structural elements." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/15926.
Full textAbstract:
A novel type of precast, prestressed concrete structural element is being implemented in load-bearing systems in buildings. These structural elements combine the use of high-performance, self-consolidating concrete (HPSCC) and non-corroding carbon fibre reinforced polymer (CFRP) prestressing tendons; this produces highly optimized, slender structural elements with excellent serviceability and (presumed) extended service lives. More widely, the use of new construction techniques, innovative materials, and ground-breaking designs is increasingly commonplace in today's rapidly evolving building construction industry. However, the performance of these and other structural elements in fire is in general not well known and must be understood before these can be used with confidence in load-bearing applications where structural fire resistance is a concern. Structural fire testing has traditionally relied on the use of the standard fire resistance test (i.e. furnace test) for assuring regulatory compliance of structural elements and assemblies, and in many cases also for developing the scientific understanding of structural response to fire. Conceived in the early 1900s and fundamentally unchanged since then, the standard testing procedure is characterized by its high cost and low repeatability. A novel test method, the Heat-Transfer Rate Inducing System (H-TRIS), resulting from a mental shift associated with controlling the thermal exposure not by temperature (e.g. temperature measured by thermocouples) but rather by the time-history of incident heat flux, was conceived, developed, and validated within the scope of the work presented in this thesis. H-TRIS allows for experimental studies to be carried out with high repeatability, imposing rationally quantifiable thermal exposure, all at low economic and temporal cost. The research presented in this thesis fundamentally seeks to examine and understand the behaviour of CFRP prestressed HPSCC structural elements in fire, with emphasis placed on undesired 'premature' failure mechanisms linked to the occurrence of heat-induced concrete spalling and/or loss of bond between the pretensioned CFRP tendons and the concrete. Results from fire resistance tests presented herein show that, although compliant with testing standards, temperature distributions inside furnaces (5 to 10% deviation) appear to influence the occurrence of heat-induced concrete spalling for specimens tested simultaneously during a single test; fair comparison of test results is therefore questionable if thermal exposure variability is not explicitly considered. In line with the aims of the research presented in this thesis, H-TRIS is used to carry out multiple comprehensive studies on the occurrence of concrete spalling and bond behaviour of CFRP tendons; imposing a quantified, reproducible and rational thermal exposure. Test results led to the conclusion that a "one size fits all" approach for mitigating the risk of heat-induced concrete spalling (e.g. prescribed dose of polypropylene (PP) fibres included in fresh concrete), appears to be ineffective and inappropriate in some of the conditions examined. This work demonstrates that PP fibre cross section and individual fibre length can have an influence on the risk of spalling for the HPSCC mixes tested herein. The testing presented herein has convincingly shown, for the first time using multiple repeated tests under tightly controlled thermal and mechanical conditions, that spalling depends not only on the thermal gradients in concrete during heating but also on the size and restraint conditions of the tested specimen. Furthermore, observations from large scale standard fire resistance tests showed that loss of bond strength of pretensioned CFRP tendons occurred at a 'critical' temperature of the tendons in the heated region, irrespective of the temperature of the tendons at the prestress transfer length, in unheated overhangs. This contradicts conventional wisdom for the structural fire safety design of concrete elements pretensioned with CFRP, in which a minimum unheated overhang is generally prescribed. Overall, the research studies presented in this thesis showed that a rational and practical understanding of the behaviour of CFRP prestressed HPSCC structural elements during real fires is unlikely to be achieved only by performing additional standard fire resistance tests. Hence, H-TRIS presents an opportunity to help promote an industry-wide move away from the contemporary pass/fail and costly furnace testing environment. Recommendations for further research to achieve the above goal are provided.
49
Leprêtre, Emilie. "Efficacité du renforcement par composites collés vis-à-vis de la propagation de fissures de fatigue pour une application aux structures rivetées." Thesis, Ecole centrale de Nantes, 2017. http://www.theses.fr/2017ECDN0003/document.
Full textAbstract:
La fatigue représente la deuxième cause d’endommagement des structures métalliques anciennes après la corrosion. Celle-ci se manifeste par l’apparition de fissures, dans les zones fortement sollicitées présentant des concentrations de contraintes importantes, et peut mener à terme à la ruine de l’ouvrage. Dans le cas des structures métalliques anciennes, les fissures de fatigue s’amorcent généralement au droit des trous de rivets rendant difficile leur détection par les techniques de contrôle non destructif conventionnelles. De même, les matériaux métalliques anciens de la construction, et notamment le fer puddlé, limitent l’utilisation de certaines techniques. Dans le cadre de ce travail de thèse, l’objectif principal est d’étudier l’efficacité d’un renforcement par composites collés dans le cas de fissures de fatigue émanant de trous de rivets. Pour cela, des éprouvettes de petites dimensions, présentant un perçage central et une unique fissure de fatigue en bord de perçage, ont été considérées. De même, deux matériaux métalliques, acier doux et fer puddlé, ainsi que deux procédés de renforcement PRFC (polymères renforcés de fibres de carbone), à Module Normal et à Ultra Haut Module, sont étudiés. Pour chaque procédé de renforcement, différentes configurations de renforcement ont été testées et notamment la mise en précontrainte du plat composite MN avant collage. Cela a permis de mettre en évidence l’efficacité de la technique de collage de plats PRFC pour un renforcement à la fatigue de matériaux métalliques anciens. Par ailleurs, les expressions analytiques simples proposées pour le facteur d’intensité de contraintes pourront par la suite être utilisés pour une application aux structures rivetées en tenant compte de la présence du rivet ainsi que celle des plaques assemblées<br>After corrosion, fatigue phenomenon is the main cause of damage in old metallic structures. Fatigue cracks appear in stress concentration area subject to high stresses, and can lead to the ruin of the bridge. In old metallic structures, fatigue cracks mainly occur at the edge of the rivet hole and are thus difficult to detect with the common non-destructive inspection technique (NDI). Moreover, due to the poor quality of the old metallic materials, particularly puddled iron, some of the NDI techniques cannot be used. The main objective of the present work is to study the effectiveness of carbon fibre reinforced polymer (CFRP) laminates in reinforcing fatigue crack emanating from the rivet hole. Thus, investigations on small-scale specimens were done. These specimens consist of metallic plates with center hole from which one single crack emanates. Two metallic materials, puddled iron and mild steel, and two reinforcement processes were used. These reinforcement processes consist of Normal Modulus (NM) and Ultra High Modulus (HHM) CFRP laminates. Furthermore, symmetrical and un-symmetrical reinforcement configurations are considered as well as pre-stressing NM laminates before application. The experimental results showed firstly the efficiency of the different studied reinforcement configurations in slowing down crack propagation. In conclusion of this work, the achieved results, particularly those in terms of Stress Intensity Factor, could be used for reinforcement of riveted structures by CFRP bonding, taking into account the presence of rivets as well as the presence of the others elements of the assembly
50
Pérez, Galmés Magdalena. "Analysis and development of experimental characterization methodologies of mode II fracture toughness on CFRP bonded joints." Doctoral thesis, Universitat de Girona, 2018. http://hdl.handle.net/10803/664508.
Full textAbstract:
Adhesives have been shown to be an excellent solution for joining fibre reinforced polymer (FRP) components thanks to their capacity to redistribute loads, reduces stress concentrations and contribute to overall weight saving in the structure. The most relevant mechanical property in adhesive bonded joints design is the shear (mode II) fracture toughness of the adhesive.
The application of the existing mode II delamination standards to adhesive joints entails some major limitations that result in severe under/over estimations of the adhesive properties and, in many cases, can even prevent results from being obtained from tests.
The main objective of the present thesis is to develop robust tools for the determination of shear (mode II) facture toughness in adhesive joints. This includes studying data reduction methods as well as the test geometries<br>Els adhesius han demostrat ser una magnífica solució per unir components de polímers reforçats amb fibres (FRP) gràcies a la seva capacitat per redistribuir càrregues, reduir les concentracions de tensions i contribuir a l’estalvi general de pes en l’estructura. La propietat mecànica més rellevant en el disseny d’unions adhesives és la tenacitat a la fractura a tallant (mode II) de l’adhesiu.
L’aplicació dels actuals assajos estandaritzats a les unions adhesives pot derivar en estimacions errònies, per sota o per sobre, de les propietats adhesives i, en molts casos, evitar que l’assaig es pugui realitzar satisfactòriament.
L’objectiu principal d’aquesta tesi és el desenvolupament d’eines robustes per a la determinació de la tenacitat a la fractura a tallant (mode II) d’unions adhesives. S’estudia l’aplicabilitat dels mètodes d’assaig de deslaminació en mode II existents a les unions adhesives estructurals. Això inclou l’estudi dels mètodes de reducció de dades i de les geometries d’assaig