Academic literature on the topic 'Shear Lag Model'
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Journal articles on the topic "Shear Lag Model"
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Ma, Yu Pu, Xin Zhi Lin, Qing Fen Li, and Zhen Li. "A Damage Model Containing Delamination in Composite Laminates." Key Engineering Materials 324-325 (November 2006): 43–46. http://dx.doi.org/10.4028/www.scientific.net/kem.324-325.43.
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When stress is high, delaminate damage can be induced by transverse cracks. A complete parabolic shear-lag damage model containing delamination induced by transverse cracks is therefore proposed and applied to predict the stiffness reduction by transverse cracking in cross-ply laminated composite materials. The predictions of the complete parabolic shear-lag analysis model, the incomplete parabolic shear-lag analysis model, and the complete parabolic shear-lag damage model containing delamination proposed in this paper have been compared. Results show that the young’s modulus reduction values obtained by our analysis model are better agreement with the experimental ones than other models.
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Bhalla, Suresh K., and Sumedha Moharana. "Modelling of Piezo-Bond Structure System for Structural Health Monitoring Using EMI Technique." Key Engineering Materials 569-570 (July 2013): 1234–40. http://dx.doi.org/10.4028/www.scientific.net/kem.569-570.1234.
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During the last two decades, active research has gone into the theoretical and the practical aspects of the electro-mechanical impedance (EMI) technique for structural health monitoring (SHM).This paper reviews the theoretical developments in modelling the force transfer mechanism between the piezoelectric-ceramic (PZT) patch and the host structure pertinent to the EMI technique. The review covers the modelling efforts spanning about last one and a half decades. The models reviewed include the shear lag based model, simplified shear lag model, the refined shear lag model and the continuum shear lag model. The first three listed models ignored the inertia term. The last model, that is the continuum based model, takes care of all the piezo, structural and adhesive effects rigorously and simultaneously. Typical comparisons between the outcomes resulting from the models are discussed.
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Nairn, John A., and H. Daniel Wagner. "A Revised Shear-Lag Analysis of an Energy Model for Fiber-Matrix Debonding." Advanced Composites Letters 5, no. 5 (September 1996): 096369359600500. http://dx.doi.org/10.1177/096369359600500501.
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A shear-lag analysis based on energy is used to predict the amount of debonding that occurs when a fiber fragment breaks into two fragments. The shear-lag analysis reproduces all features of more sophisticated analyses. A drawback of the shear-lag analysis, however, is that it depends on an unknown parameter which can be expressed in terms of an effective fiber volume fraction. If the effective fiber volume fraction can be determined (by experiments or by advanced stress analyses), the shear-lag model can be used to interpret debonding experiments.
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Nairn, J. A. "Generalized Shear-Lag Analysis Including Imperfect Interfaces." Advanced Composites Letters 13, no. 6 (November 2004): 096369350401300. http://dx.doi.org/10.1177/096369350401300601.
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Two recent papers showed that shear-lag analysis can be an effective tool for stress analysis of composites when done properly and when applied to problems for which it is appropriate. This paper extends the prior analysis of concentric cylinders to a generalized shear-lag analysis in which the transverse variations of shear stress are described by arbitrary shape functions. The shear-lag analysis and solution can be derived in terms of averages of the new shape functions. The shape functions can be specified after analysis and tailored to suit specific problems. This paper also extends shear-lag analysis of both concentric cylinders and multilayered structures to model imperfect interfaces between the layers. The generalized methods were applied to several issues in fibre/matrix stress transfer modelled as two concentric cylinders. By modifying prior shape functions, it was possible to extend shear-lag analysis to work for any fibre volume fraction. Prior shear-lag models were all unacceptable at low fibre volume fraction. The full shear-lag analysis can model stress transfer for both isotropic and anisotropic fibres. The new imperfect interface capability was used to interpret experimental results for fibre/matrix stress transfer in terms of interface quality.
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Zhao, Pinglao, and Shaocheng Ji. "Refinements of shear-lag model and its applications." Tectonophysics 279, no. 1-4 (September 1997): 37–53. http://dx.doi.org/10.1016/s0040-1951(97)00129-7.
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Luo, Q. Z., Y. M. Wu, Q. S. Li, J. Tang, and G. D. Liu. "A finite segment model for shear lag analysis." Engineering Structures 26, no. 14 (December 2004): 2113–24. http://dx.doi.org/10.1016/j.engstruct.2004.07.010.
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Lu, Hailin, Heng Cai, Zheng Tang, and Zijun Nan. "Experimental study and finite element analysis on shear lag effect of thin-walled curved box beam under vehicle loads." MATEC Web of Conferences 169 (2018): 01040. http://dx.doi.org/10.1051/matecconf/201816901040.
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Shear lag effects of curved box beam under vehicle loads are investigated by using three-dimensional finite element method, where 4 parameters of vehicle loads, load size, vehicle speed, vehicle load position, load types, are considered. The change rules of stress distribution and shear lag coefficients of upper flange at mid-span are obtained when the loads move to the mid-span. The results indicate that under vehicle loads, the peak shear lag coefficients is at the junction between the flange and web, shear lag effect is prominent, shear lag effect is greatly influenced by vehicle speed and vehicle load position, while load size and load types almost don’t affect shear lag coefficients but do affect the stress. The model experiment of a cantilever curved box beam is carried out to compare with finite element analysis, and the error between them is small, which testify the validity and reliability of finite element model.
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Kumar, S., and M. A. Khan. "A shear-lag model for functionally graded adhesive anchors." International Journal of Adhesion and Adhesives 68 (July 2016): 317–25. http://dx.doi.org/10.1016/j.ijadhadh.2016.04.010.
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Yu, J., S. W. Hu, Y. C. Xu, and B. Fan. "Coupled Mechanism on Interfacial Slip and Shear Lag for Twin-Cell Composite Box Beam Under Even Load." Journal of Mechanics 34, no. 5 (September 14, 2017): 601–16. http://dx.doi.org/10.1017/jmech.2017.77.
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AbstractA model of Twin-cell Composite Box Beam (TCCBB), which is composed of concrete plate and thin-walled steel box beam with twin-cell, is proposed in this paper. Combined with structural features, longitudinal interfacial slip mode (LISM) and related shear hysteresis functions (SHFS) of this TCCBB model are defined respectively; analytical formulation describing combination effect between interfacial slip and shear lag is launched for this TCCBB model under even load. Based on established governing differential equations and its relative boundary conditions (calculated with compatible mechanism of interfacial slip and shear lag effect), closed form solutions of normal stress and shear stress are derived for this TCCBB model, as well as effective shear-lag coefficient and effective coupled behavior coefficient. To obtain more accurate computational results of specific coupled mechanism of this TCCBB model, numerical example is carried out to analyze and predict coupled mechanism of interfacial slip and shear lag effect for this type of composite structures.
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Xiong, Xiaoshuang, Shirley Z. Shen, Lin Hua, Xiang Li, Xiaojin Wan, and Menghe Miao. "Predicting tensile behaviors of short flax fiber-reinforced polymer–matrix composites using a modified shear-lag model." Journal of Composite Materials 52, no. 27 (April 6, 2018): 3701–13. http://dx.doi.org/10.1177/0021998318769128.
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Natural fiber-reinforced composites are increasingly being used in the industry. The fiber–matrix interfacial properties of the composites are influenced by many factors, including chemical treatment of the natural fiber, type of polymer matrix, composites fabrication method, and process and the service environment of the composites. In this paper, a modified shear-lag model based on a cohesive fiber/matrix interface is proposed and applied to the analysis of the stress–transfer characteristics and the tensile properties of unidirectional short flax fiber-reinforced composites. The model takes into account of the interfacial shear stiffness, bonding strength between fiber end face and matrix, fiber aspect ratio and fiber volume fraction. 3D finite element models of the composites using a cohesive zone method are used to verify the accuracy of the modified shear-lag model. The fiber tensile strength and the composite tensile elastic modulus are significantly influenced by the interfacial shear stiffness, fiber aspect ratio, and fiber volume fraction. The bonding strength between the fiber end face and the matrix only has an effect when the interfacial shear stiffness is low. The predicted results from the modified shear-lag model show good agreement with the finite element analysis and experimental results in the literature. The modified cohesive shear-lag model provides a simple and effective method for analyzing fiber axial stress, shear stress in the fiber/matrix interface, and tensile elastic modulus of the final composite.
Dissertations / Theses on the topic "Shear Lag Model"
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Rezaei, Mojdehi Ahmad. "Experimental and Theoretical Studies of Friction and Adhesion of Elastomeric Materials." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/79818.
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In this dissertation, four distinct but in some ways related topics, mostly related to experimental and theoretical investigations of friction and adhesion of elastomeric materials, are presented. First, an experimental and theoretical study of the interaction between elastic beams and granular media under compressive loading is performed. Buckling loads of beams with different dimensions and boundary conditions within granular media of different depths and grain sizes are measured, and theoretically approximated using the Ritz energy approach, based on the concept of beam on an elastic foundation. Several nondimensional parameters and a scaling law are derived to characterize different interaction regimes between the beams and granular support. The findings from this work is believed to be helpful for improved understanding of interactions between elastic beams and surrounding elastic foundation with applications to piles, oil pipelines, and robotic needle insertion into soft tissues. Second, the role of axial compliance on the friction of extensible strips is investigated. Significant changes were observed in the static and kinetic friction of strips, when the effective axial compliance was changed. The underlying causes of the changes in the frictional response are explained and quantitatively predicted using an extended shear lag model. We believe that this study provides insights into the effect of axial compliance on the frictional response of materials, paving the way for design and optimization of systems where the static and kinetic friction forces play an important role. Third, the effect of normal force and rate on the kinetic friction of two different elastomers, namely acrylic and silicone-based elastomers is evaluated. A custom-built pendulum test setup was used to perform the friction test in dynamic conditions. Two substantially different responses with respect to the change in normal force were observed and the role of different contributions to the frictional response of viscoelastic materials, i.e. bulk hysteresis friction, adhesion friction, and cohesion friction, are discussed. Different scenarios such as modifying the surface by using graphite powder, reducing test velocity, and also performing drop tests to characterize the surface hysteresis of the elastomers, were considered to further explore the origin of frictional responses of the elastomers. This study could improve insights gained from Dynamic Mechanical Analysis (DMA) data when obtaining and interpreting the effect of normal force on kinetic COF of elastomers with potential applications to
tires, shoes, etc. where friction plays an important role. Last, a generalized scaling law, based on the classical fracture mechanics approach, is developed to predict the bond strength of adhesive systems. The proposed scaling law, which depends on the rate of change of bond area with compliance, is in apparent discrepancy with the previously reported scaling relationship that depends on the ratio of area to compliance. This distinction can have a profound impact on the expected bond strength of systems, particularly when failure mechanism changes or the compliance of the load train is increased. Furthermore, the shear lag model is implemented to derive a closed-form relation for the system compliance and the conditions where the two models deviate from each other are discussed and demonstrated. The results obtained from this approach could lead to a better understanding of the relationship between the bond strength and the geometry and mechanical properties of adhesive systems, with applications to different types of adhesive joints such as bio-inspired adhesive, biomedical adhesive tapes, and structural adhesive joints.Ph. D.
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Dang, Wengang. "Shear behavior of plane joints under CNL and DNL conditions: Lab testing and numerical simulation." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2017. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-227649.
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The aim of this research work is to deepen the understanding of joint shear behavior under different boundary conditions. For this purpose, joint closure tests under quasi-static and dynamic conditions, direct shear and cyclic shear tests under CNL and DNL boundary conditions of plane joints are performed using GS-1000 big shear box device. The dissertation also presents the procedure to simulate the shear box device and simulating the behavior of plane joints at the micro-scale using FLAC3D. Special attention has been given to understand the influencing factors of the normal stress level, direct shear rate, horizontal cyclic shear frequency, normal impact frequency, horizontal cyclic shear displacement amplitude and vertical impact force amplitude.
Lab test and numerical simulation results show that the quasi-static joint stiffness increases with increasing normal force. Dynamic joint stiffness decreases with increasing superimposed normal force amplitudes. Normal impact frequencies have little influence on the joint stiffness. Rotations and stress changes at the plane joint during shearing are proven. Rotations and development of stress gradients can be decreased significantly by increasing the size of the bottom specimen and applying a shear velocity at the upper shear box and normal loading piston. Furthermore, peak shear force increases with increasing normal force. Friction angle of cyclic shear tests is smaller than that of direct shear tests. Moreover, significant time shifts between normal and shear force (shear force delay), normal force and friction coefficient (friction coefficient delay) during direct shear tests under DNL boundary conditions are observed and the reference quantity ‘shear-velocity-normal-impact-frequency’ (SV-NIF) to describe the behavior under DNL boundary conditions is defined. Peak shear force and minimum friction coefficient increase with increasing SV-NIF. Relative time shift between normal force and shear force decreases with increase of SV-NIF. The mechanical behavior of the GS-1000 big shear box device is simulated and the loss of normal force caused by the tilting of the loading plate is quantified.
Finally, the novel direct and cyclic shear strength criterions under DNL conditions are put forward. The shear strength criterions are in close agreement with the measured values, which indicates that the novel shear strength criterions are able to predict the shear strength under DNL conditions.
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Lang, Robert Friedrich [Verfasser], Wolfram [Akademischer Betreuer] Weise, and Nora [Akademischer Betreuer] Brambilla. "Shear Viscosities from Kubo Formalism in a Large-Nc Nambu--Jona-Lasinio Model / Robert Friedrich Lang. Gutachter: Wolfram Weise ; Nora Brambilla. Betreuer: Wolfram Weise." München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1070981508/34.
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Machado, Sandro Lemos. "Aplicação de conceitos de elastoplasticidade a solos não saturados." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-24092018-164904/.
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Neste trabalho são apresentados resultados de ensaios triaxiais convencionais, de compressão confinada e triaxiais com controle de tensão, realizados em amostras saturadas e com controle de sucção, em corpos de prova indeformados coletados ao longo de um perfil típico de solo da cidade de São Carlos - SP. A partir dos dados obtidos, faz-se um estudo do comportamento de deformação e resistência do solo, em condições não saturadas, ao longo de todo perfil amostrado. Para o solo residual de arenito realiza-se também um estudo das suas principais características de elastoplasticidade, para a condição saturada e para o caso dos ensaios realizados com controle de sucção. Mostra-se que as superfícies de plastificação obtidas para o solo podem ser ajustadas de modo razoável pela superfície de escoamento do Cam-Clay modificado, utilizada nos modelos de Alonso et al. (1990) e Balmaceda et al. (1992). Para esta superfície, o uso de uma lei de fluxo associada conduziu a resultados satisfatórios. Um modelo constitutivo é proposto para representação do comportamento do solo em condições não saturadas. Uma nova superfície de plastificação e uma nova lei de fluxo (não associada) são propostas para o solo, conseguindo-se uma melhor previsão dos pontos de escoamento situados à esquerda da projeção da linha de estados críticos e diminuindo-se os valores dos desvios angulares dos vetores de incrementos de deformação plástica. No modelo constitutivo proposto neste trabalho, a superfície de escoamento LC do solo é obtida levando-se em consideração não somente os valores da pressão de pré-adensamento, mas também os valores de γ(s). Os modelos constitutivos proposto e de Balmaceda et al. (1992) são utilizados na simulação dos ensaios de laboratório, obtendo-se bons resultados. Com o uso dos parâmetros adotados para a simulação dos ensaios de laboratório são realizadas previsões do comportamento de estruturas de fundação em campo, obtendo-se resultados satisfatórios.This thesis deals with the application of elasto-plastic concepts to a typical non saturated soil from São Carlos - SP. The soil profile analysed is composed at is upper part of a sandy soil of coluvium origin and of a residual soil from sandstone at depths larger than 8 m. The water level is at a depth of about 10 m. The experimental work included compression triaxial tests following different stress paths and confined compression tests performed both on saturated and on unsaturated specimens. In the case of the residual soil of sandstone, its main elastoplastic characteristics are studied. It is shown that yield points can be fairly fitted by the yield surface proposed by of Alonso et al. (1990) and Balmaceda et al. (1992), which are an extension of modified Cam-Clay yield surface. In this case, an associated flow law also gave reasonable results in reproducing experimental data. In order to get a better adjustment between experimental and theoretical results, a new constitutive model is proposed using a new yield surface and a non associated flow law. It is shown that this new yield surface can better adjust experimental yield points, mainly those located at left of the critical state line (C.S.L.) and the new flow rule leaded to lower deviation of incremental plastic strain vectors. In the proposed model, the yield surface LC is obtained considering both γ(s) and po experimental values. The proposed and Balmaceda et al. (1992) models were utilised to predict the laboratory soil behaviour, showing good results. The parameters already used to reproduce laboratory tests were also used to model foundation structures built in the soil studied and a fair agreement between experimental and predict results was obtained.
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Jawdhari, Akram Rasheed. "BEHAVIOR OF RC BEAMS STRENGTHENED IN FLEXURE WITH SPLICED CFRP ROD PANELS." UKnowledge, 2016. http://uknowledge.uky.edu/ce_etds/37.
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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.
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Rahm, Jens. "Beitrag zur Herstellung langfaserverstärkter Aluminium-Matrix-Verbundwerkstoffe durch Anwendung der Prepregtechnik." Doctoral thesis, Universitätsbibliothek Chemnitz, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200800719.
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In Kenntnis der beschriebenen verfahrenstechnischen Einflussfaktoren auf die Struktur und die Eigenschaften der faserverstärkten MMC geht es darum, ein prepregtechnologisches Verfahren für das Herstellen lang- bzw. endlosfaserverstärkter MMC mit Aluminiummatrix zu erarbeiten und die Machbarkeit im Hinblick auf die Reproduzierbarkeit und das Erreichen der prinzipiell möglichen mechanischen Eigenschaftskennwerte nachzuweisen. Es geht darum, den Einfluss der Prozessparameter auf die Struktur der Prepregs und der verdichteten MMC`s zu erfassen und zu bewerten. In Kenntnis dieser Zusammenhänge sind die qualitätsrelevanten Kennwerte der Werkstoffstruktur denen der mechanischen Eigenschaften gegenüberzustellen. In Weiterführung der o.g. Darstellungen zwischen Struktur- und Eigenschaften der Verbundwerkstoffe geht es darum, die experimentell bestimmten Kennwerte der Festigkeit und des E-Moduls auf Übereinstimmung mit den entsprechenden Korrelationsmodellen (Shear Lag Modell, Grenzwert- und Modellkonzept, EIAS-Methode) zu überprüfen. Ferner geht es darum, die Zusammenhänge zwischen den im Modell definierten idealen Gefügebedingungen mit den realen im Hinblick auf deren Einfluss auf die Eigenschaftskennwerte kritisch zu diskutieren. Aufbauend auf den definierten Zielstellungen kann nach der erfolgten Bewertung aller Untersuchungsergebnisse gezeigt werden, dass die entworfene Technologie zur Herstellung langfaserverstärkter Metallmatrix-Verbundwerkstoffe dazu geeignet ist, Fasern mit geringem Durchmesser und hoher Flexibilität (am Beispiel der hochfesten Kohlenstofffasern vom Typ HTA 5131) mit dem ausgewählten Matrixmetall (am Beispiel der AlSi5-Legierung) zunächst zu Prepregs und weiterhin in verdichtete Verbundstrukturen zusammenzuführen. Das vergleichende Gegenüberstellen von Simulation und Experiment dienen einerseits dem Verifizieren der Prozessmodelle. Die Prozessmodelle stellen andererseits die wertvolle versuchstechnische Grundlage zur Definition und auch der Einengung des Arbeitsfensters für die Prozessparameter und der Anzahl erforderlicher Verifikationsexperimente im Hinblick auf die Probebeschichtungen und deren Auswertung dar. Derartige Modelle leisten eine wichtige Hilfestellung zum weiteren Erhöhen der Prozessstabilität und damit auch dem Nachweis der ReproduzierbarkeitThe aim of this work is a described prepreg-technological method to create aluminium based MMC reinforced with continuous fibres and the verification of reproducibility to achieve relevant mechanical properties. This aim is based on the knowledge of technological influences on structure and properties of fibre reinforced MMC. And so activities are focussed on the evaluation of the influence of process functions on structure and mechanical properties of prepregs and compacted MMC. The comparison between structure and properties is necessary to describe the correlation function of composite material. Furthermore the application of different correlation models (“Shear Lag”, “Grenzwert- Modellkonzept“, “EIAS”) to describe the influence of composite structures on strength and Young`s modulus is necessary to compare theoretical results with those of relevant experiments. The object is a critical quantification of the influence of real structure parameters compared with those of a model defined structure. In view of the described aim it is shown that the described technology to manufacture long fibre reinforced MMC is applicable for preparation of carbon fibres (HTA 5131) with low diameter and high flexibility and metal matrix (AlSi5) to prepregs and compact composites. The comparison of simulated and experimental results is the base for verification of different process models. So it is possible to describe and optimize the process function and moreover to minimize the number of technological experiments. After optimization specified models are a good base to achieve a high level of stability and reproducibility for all steps in prepreg technology
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Slade, Robert Arthur. "Failure Analysis of Impact-Damaged Metallic Poles Repaired With Fiber Reinforced Polymer Composites." Master's thesis, University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5505.
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Metallic utility poles, light poles, and mast arms are intermittently damaged by vehicle collision. In many cases the vehicular impact does not cause immediate failure of the structure, but induces localized damage that may result in failure under extreme service loadings or can promote degradation and corrosion within the damaged region. Replacement of these poles is costly and often involves prolonged lane closures, service interruption, and temporary loss of functionality. Therefore, an in situ repair of these structures is required. This thesis examines the failure modes of damaged metallic poles reinforced with externally-bonded fiber reinforced polymer (FRP) composites. Several FRP repair systems were selected for comparison, and a set of medium and full-scale tests were conducted to identify the critical failure modes. The material properties of each component of the repair were experimentally determined, and then combined into a numerical model capable of predicting global response. Four possible failure modes are discussed: yielding of the unreinforced substrate, tensile rupture of the FRP, compressive buckling of the FRP, and debonding of the FRP from the substrate. It was found that simple linear, bilinear, and trilinear stress-strain relationships accurately describe the response of the composite and substrate components, whereas a more complex bond-slip relationship is required to characterize debonding. These constitutive properties were then incorporated into MSC.Marc, a versatile nonlinear finite element program. The output of the FEM analysis showed good agreement with the results of the experimental bond-slip tests.ID: 031001508; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Adviser: Kevin R. Mackie.; Title from PDF title page (viewed August 5, 2013).; Thesis (M.S.)--University of Central Florida, 2012.; Includes bibliographical references (p. 101-103).
M.S.
Masters
Civil, Environmental, and Construction Engineering
Engineering and Computer Science
Civil Engineering; Structural and Geotechical Engineering
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DiFelice, Ronald Attilio. "An Investigation of Plasma Pretreatments and Plasma Polymerized Thin Films for Titanium/Polyimide Adhesion." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/27348.
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Plasma pretreatments are environmentally benign and energy efficient processes for modifying the surface chemistry of materials. In an effort to improve the strength of the titanium alloy/FM-5 polyimide adhesive joint for aerospace applications, oxygen plasma pretreatments and novel thin plasma polymerized (PP) films were investigated as adhesion promoters. Plasma treatments were carried out using custom-built, low pressure, radio frequency, inductively coupled plasma reactors. Ti-6Al-4V coupons were plasma treated and used to prepare miniature single lap shear (SLS) joints. The effects of plasma pretreatments on surface chemistry were studied using x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), Fourier transform infrared analysis (FTIR), and contact angle measurements. Relationships between composition, mechanical properties, and adhesion of PP films on Ti-6Al-4V and silicon wafers were investigated. The nanomechanical properties (modulus, hardness and adhesion) were studied using atomic force microscopy (AFM) nanoindentation and nanoscratch testing.
A design of experiments (DOE) three factorial model was used to optimize the parameters for oxygen plasma treatments. Oxygen plasma pretreatments enhanced joint strength by cleaning the titanium surface and creating an extended oxide layer. Nanoindentation of oxygen plasma treated substrates showed no change in the surface mechanical properties due to the oxygen plasma treatment. This suggested that the improved SLS strength of the oxygen plasma pretreated substrates was due to the cleaning of the substrate and the removal of carbonaceous contaminants, rather than any changes in the morphology of the oxide layer.
PP acetylene films were predominantly carbon, with oxygen as the other main constituent (incorporated mostly as C-O and C=O). For all SLS specimens tested, the adhesion between PP acetylene and FM-5 adhesive was adequate. However, the strength of SLS joints was limited by the adhesion of the PP acetylene to the Ti-6Al-4V substrate. The effects of a large number of plasma parameters, such as substrate pretreatment, carrier gas, input power, flow rate and film thickness were investigated. All samples failed at the PP film/Ti-6Al-4V interface or within the PP acetylene film, and thicker PP films yielded lower SLS strengths. PP films deposited at lower power exhibited higher hardness and reduced modulus than films deposited at higher power. Overall, thinner films exhibited higher hardness and reduced Young's modulus than thicker films. PP films of higher hardness yielded higher critical loads at debond (thickness normalized) during the nanoscratch test.
Thin films were developed via the vapor plasma polymerization of titanium(IV) isobutoxide (TiiB). XPS results suggested that titanium was incorporated into the film as TiO2 clusters dispersed in an organic matrix. No evidence for Ti-C was obtained from the XPS spectra. PP films of TiiB were much more compliant than PP acetylene films. This behavior was attributed to decreased fragmentation and lower crosslinking that occurred during PP TiiB film deposition. These PP films did not exhibit sol-gel-like qualities, and because of the way titanium was incorporated into the films, a more appropriate name for these films might be "titanium dioxide-doped plasma polymerized films."Ph. D.
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Chaloupka, Martin. "Vliv účinků poddolování na volbu typu nosné konstrukce mostu v km 332,420 trati Dětmarovice - Č. Těšín." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2012. http://www.nusl.cz/ntk/nusl-225534.
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The aim of the master’s thesis was t odevelop alternative solutions supporting steel structure of the railway bridge on the undermined area. The range of single fields were chosen based on the location of existing substructures. Reducing the width of bridge openings were not allowed. Based on the geodetic survey plans were drawn up clear of the current state. On the basis of specifications for developing a detailed process was chosen variant Gerber’s beam reinforced with an arch in mean field. For this variant was performed structural analysis of the main parts of the main structure of the bridge, which was calculated with the effects of undermining. For variant Gerber’s beam were made clear drawings and drawing details of the selected steel bridge construction (new state). Further, detailed analysis of selected structural detail was made. Specifically, connecting rod to the main beam, which was designed optimal shape and thickness of the joints plate with a suitable radius of the firing to avoid plastification of the material in this area. Variant of the continuous beam without joints was prepared to. It has been observed, what is the effect of undermining on the stress in the construction of the bridge - was confronted with the effects on Gerber’s beam. To reduce stress in the construction of the bridge and compliance of ultimate state of applicability of the main beam has been designed bearing adjustment and after considering several options its implementation too. The economic comparison between the two variants was conducted. The assembling procedure was designed for both types of bridge structures. In the technical report we can read about due to the intention of building a new bridge and further we can find there other important technical information. In conclusion of the master’s thesis there has been recommended for the construction specific variant – from the perspective of an investor, and from the static aspect-view of the designer.
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Dang, Wengang. "Shear behavior of plane joints under CNL and DNL conditions: Lab testing and numerical simulation." Doctoral thesis, 2016. https://tubaf.qucosa.de/id/qucosa%3A23133.
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The aim of this research work is to deepen the understanding of joint shear behavior under different boundary conditions. For this purpose, joint closure tests under quasi-static and dynamic conditions, direct shear and cyclic shear tests under CNL and DNL boundary conditions of plane joints are performed using GS-1000 big shear box device. The dissertation also presents the procedure to simulate the shear box device and simulating the behavior of plane joints at the micro-scale using FLAC3D. Special attention has been given to understand the influencing factors of the normal stress level, direct shear rate, horizontal cyclic shear frequency, normal impact frequency, horizontal cyclic shear displacement amplitude and vertical impact force amplitude.
Lab test and numerical simulation results show that the quasi-static joint stiffness increases with increasing normal force. Dynamic joint stiffness decreases with increasing superimposed normal force amplitudes. Normal impact frequencies have little influence on the joint stiffness. Rotations and stress changes at the plane joint during shearing are proven. Rotations and development of stress gradients can be decreased significantly by increasing the size of the bottom specimen and applying a shear velocity at the upper shear box and normal loading piston. Furthermore, peak shear force increases with increasing normal force. Friction angle of cyclic shear tests is smaller than that of direct shear tests. Moreover, significant time shifts between normal and shear force (shear force delay), normal force and friction coefficient (friction coefficient delay) during direct shear tests under DNL boundary conditions are observed and the reference quantity ‘shear-velocity-normal-impact-frequency’ (SV-NIF) to describe the behavior under DNL boundary conditions is defined. Peak shear force and minimum friction coefficient increase with increasing SV-NIF. Relative time shift between normal force and shear force decreases with increase of SV-NIF. The mechanical behavior of the GS-1000 big shear box device is simulated and the loss of normal force caused by the tilting of the loading plate is quantified.
Finally, the novel direct and cyclic shear strength criterions under DNL conditions are put forward. The shear strength criterions are in close agreement with the measured values, which indicates that the novel shear strength criterions are able to predict the shear strength under DNL conditions.
Book chapters on the topic "Shear Lag Model"
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Kimura, Souta, Jun Koyanagi, Takayuki Hama, and Hiroyuki Kawada. "An Improved Shear-Lag Model for a Single Fiber Composite with a Ductile Matrix." In Advances in Composite Materials and Structures, 333–36. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-427-8.333.
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Dupuy, J. S., F. Lachaud, R. Piquet, and J. Huet. "Finite Element Model Matching Based on Optical Measurement Fields on Single Shear Lap Joint." In Application of Imaging Techniques to Mechanics of Materials and Structures, Volume 4, 53–62. New York, NY: Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4419-9796-8_8.
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Wang, Huan. "Non-Steady First Matrix Cracking of Fiber-Reinforced Ceramics." In Safety and Risk Assessment of Civil Aircraft during Operation. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.93060.
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Matrix cracking affects the reliability and safety of fiber-reinforced ceramic-matrix composites during operation. The matrix cracking can be divided into two types, that is, steady state crack and non-steady state cracking. This chapter is about the non-steady stable cracking of fiber-reinforced CMCs. The micro stress field of fiber, matrix, and interface shear stress along the fiber direction is analyzed using the shear-lag model. The relationship between the crack opening displacement and the crack surface closure traction is derived. The experimental first matrix cracking stress of different CMCs are predicted.
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Albattat, Rami, and Hussein Hoteit. "Modeling Lost-Circulation into Fractured Formation in Rock Drilling Operations." In Drilling Technology. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.95805.
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Loss of circulation while drilling is a challenging problem that may interrupt drilling operations, reduce efficiency, and increases cost. When a drilled borehole intercepts conductive faults or fractures, lost circulation manifests as a partial or total escape of drilling, workover, or cementing fluids into the surrounding rock formations. Studying drilling fluid loss into a fractured system has been investigated using laboratory experiments, analytical modeling, and numerical simulations. Analytical modeling of fluid flow is a tool that can be quickly deployed to assess lost circulation and perform diagnostics, including leakage rate decline and fracture conductivity. In this chapter, various analytical methods developed to model the flow of non-Newtonian drilling fluid in a fractured medium are discussed. The solution methods are applicable for yield-power-law, including shear-thinning, shear-thickening, and Bingham plastic fluids. Numerical solutions of the Cauchy equation are used to verify the analytical solutions. Type-curves are also described using dimensionless groups. The solution methods are used to estimate the range of fracture conductivity and time-dependent fluid loss rate, and the ultimate total volume of lost fluid. The applicability of the proposed models is demonstrated for several field cases encountering lost circulations.
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Kuwahara, Hiroyuki, and Chris J. Myers. "Abstraction Methods for Analysis of Gene Regulatory Networks." In Handbook of Research on Computational Methodologies in Gene Regulatory Networks, 352–85. IGI Global, 2010. http://dx.doi.org/10.4018/978-1-60566-685-3.ch015.
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With advances in high throughput methods of data collection for gene regulatory networks, we are now in a position to face the challenge of elucidating how these genes coupled with environmental stimuli orchestrate the regulation of cell-level behaviors. Understanding the behavior of such complex systems is likely impossible to achieve with wet-lab experiments alone due to the amount and complexity of the data being collected. Therefore, it is essential to integrate the experimental work with efficient and accurate computational methods for analysis. Unfortunately, such analysis is complicated not only by the sheer size of the models of interest but also by the fact that gene regulatory networks often involve small molecular counts making discrete and stochastic analysis necessary. To address this problem, this chapter presents a model abstraction methodology which systematically performs various model abstractions to reduce the complexity of computational biochemical models resulting in substantial improvements in analysis time with limited loss in accuracy.
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Filipovic, Nenad, Milos Radovic, Dalibor D. Nikolic, Igor Saveljic, Zarko Milosevic, Themis P. Exarchos, Gualtiero Pelosi, Dimitrios I. Fotiadis, and Oberdan Parodi. "Computer Predictive Model for Plaque Formation and Progression in the Artery." In Coronary and Cardiothoracic Critical Care, 220–45. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-8185-7.ch012.
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In this chapter we described predictive model for plaque formation and progression in the coronary and carotid artery. A full three-dimensional model for plaque formation and progression, coupled with blood flow and LDL concentration is analysed. The Navier-Stokes equations together with the Darcy law for model blood filtration and Kedem-Katchalsky equations are implemented. Additionally, the system of three additional reaction-diffusion equations for simulation of the inflammatory process is coupled with full incremental iterative procedure. We developed hybrid genetic algorithm for fitting parameters of ODE model for oxidized LDL, macrophage, smooth muscle cell and foam cell concentration evolution in time. The animal carotid and coronary artery after 2 month of high fat diet are examined. We compared with CT our computer model of the plaque size for three groups of patients: De-novo, Old-lesions and Control patients. Detailed shear stress distributions for baseline and follow-up for these patients are given. There is a good matching for plaque size and location.
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Filipovic, Nenad, Milos Radovic, Dalibor D. Nikolic, Igor Saveljic, Zarko Milosevic, Themis P. Exarchos, Gualtiero Pelosi, Dimitrios I. Fotiadis, and Oberdan Parodi. "Computer Predictive Model for Plaque Formation and Progression in the Artery." In Handbook of Research on Trends in the Diagnosis and Treatment of Chronic Conditions, 279–300. IGI Global, 2016. http://dx.doi.org/10.4018/978-1-4666-8828-5.ch013.
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In this chapter we described predictive model for plaque formation and progression in the coronary and carotid artery. A full three-dimensional model for plaque formation and progression, coupled with blood flow and LDL concentration is analysed. The Navier-Stokes equations together with the Darcy law for model blood filtration and Kedem-Katchalsky equations are implemented. Additionally, the system of three additional reaction-diffusion equations for simulation of the inflammatory process is coupled with full incremental iterative procedure. We developed hybrid genetic algorithm for fitting parameters of ODE model for oxidized LDL, macrophage, smooth muscle cell and foam cell concentration evolution in time. The animal carotid and coronary artery after 2 month of high fat diet are examined. We compared with CT our computer model of the plaque size for three groups of patients: De-novo, Old-lesions and Control patients. Detailed shear stress distributions for baseline and follow-up for these patients are given. There is a good matching for plaque size and location.
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Kumar, Dhiraj, Sudipta Paitandi, Arunanshu Shekhar Kuar, and Dipankar Bose. "Experimental Investigation on Laser Transmission Welding of Polycarbonate and Acrylic." In Machine Learning Applications in Non-Conventional Machining Processes, 160–80. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-3624-7.ch010.
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This chapter presents the effect of various process parameters, namely laser power, pulse frequency, and welding speed, on the weld shear strength and weld width using a diode laser system. Here, laser transmission welding of transparent polycarbonate and black carbon filled acrylic each of 2.8 mm thickness have been performed to create lap joint by using low power laser. Response surface methodology is applied to develop the mathematical model between the laser welding process parameters and the responses of weld joint. The developed mathematical model is tested for its adequacy using analysis of variance and other adequacy measures. It has been observed that laser power and welding speed are the dominant factor followed by frequency. A confirmation test has also been conducted to validate the experimental results at optimum parameter setting. Results show that weld strength of 34.3173 N/mm and weld width of 2.61547 mm have been achieved at optimum parameter setting using desirability function-based optimization technique.
Conference papers on the topic "Shear Lag Model"
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Deshmukh, D. V., and E. J. Berger. "Shear Lag Based Iwan Model for Interface Friction Contacts." In ASME 2005 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/detc2005-85328.
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Reduced order models for characterizing friction interfaces have been investigated for the last 75 years. Recent work has been focused on microslip formulation of the interface behavior, where continuous contact is approximated with a multi-point contact model. A novel multi-point contact model is presented in this work, which is entirely derived from a shear lag approach to resolve the kinematic state of the friction interface under the presence of tangential loading. Both static and dynamic loading conditions are analyzed and comparisons are drawn between the continuous and discrete models. The series Iwan model presented in this work differentiates between the elastic and friction components of the interface displacement, both parameters being calibrated using material properties and model geometry. Convergence behavior of such models with increasing model order is demonstrated. The response characteristics of the series Iwan model under dynamic loading conditions is also investigated. The series Iwan model is in good agreement with the shear lag approach for results such as propagation of the slip zone with increasing pullout force. The transient response of the the structural mass and the kinematic states of the damping elements are convergent with increasing model order.
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Dong, Yongtao, Qingbin Li, and Farhad Ansari. "Shear Lag Model for Embedded Interferometric Optical Fiber Sensors." In Engineering Mechanics Conference 2000. Reston, VA: American Society of Civil Engineers, 2000. http://dx.doi.org/10.1061/40495(302)5.
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LI, WEI-XUE, JIE ZHU, YUAN HAO, JIAN-FENG DAI, and QING WANG. "A SHEAR-LAG MODEL FOR CARBON NANOTUBE-REINFORCED MAGNESIUM MATRIX COMPOSITES." In Proceedings of the 6th International Conference on ICAMP. WORLD SCIENTIFIC, 2011. http://dx.doi.org/10.1142/9789814322799_0069.
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Salehi-Khojin, Amin, and Nader Jalili. "A Shear-Lag Model for Nanotube-Reinforced Composite Systems Under Transient Heat Transfer." In ASME 2006 Multifunctional Nanocomposites International Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/mn2006-17050.
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Understanding the stress transfer between nanotube reinforcements and matrix is an important factor in determining the overall mechanical properties of nanotube-reinforced composites. The classical shear-lag model in which the fiber and the matrix are equally long can not be applied to nanotube-based composite structures. Recently, a shear-lag model under mechanical loading for a concentric composite cylinder embedded with a capped nanotube has been introduced as the representative volume element (RVE). In this study, using similar approach the shear lag model is extended for a system under both mechanical and thermal loadings. The outer surface of RVE is prescribed to heating and cooling conditions, and transient heat transfer concept is used to find the temperature distribution in the matrix and on the surface of the nanotube. Using constitutive, geometrical and equilibrium equations for a given RVE, new shear-lag model for a nanotube-reinforced composite is then derived. It is demonstrated that the proposed model at room temperature could reduce to the same results obtained previously. These equations can be used to predict the mechanical properties of nanocomposite systems in real applications.
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Chusheng He. "Model experimental study of shear lag effect on the girder of a cable-stayed bridge." In 2011 International Conference on Electric Technology and Civil Engineering (ICETCE). IEEE, 2011. http://dx.doi.org/10.1109/icetce.2011.5774669.
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Yao, L. L., P. F. Li, and S. Wan. "Finite element analysis on shear lag effect of the test model of Chaoyanggou Reservoir Bridge." In The 5th International Conference on Civil Engineering and Urban Planning (CEUP2016). WORLD SCIENTIFIC, 2017. http://dx.doi.org/10.1142/9789813225237_0068.
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Linderman, Stephen W., Ioannis Kormpakis, Richard H. Gelberman, Victor Birman, Ulrike G. K. Wegst, Stavros Thomopoulos, and Guy M. Genin. "Shear Lag Sutures: Improved Suture Repair Through the Use of Adhesives." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-67522.
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Conventional surgical suture is mechanically limited by the ability of the suture to transfer load to tissue at suture anchor points. Sutures coated with adhesives can improve mechanical load transfer beyond the range of performance of existing suture methods, thereby strengthening orthopaedic repairs and decreasing the risk of failure. The mechanical properties of suitable adhesives were identified using a shear lag model. Examination of the design space for an optimal adhesive demonstrated requirements for strong adhesion and low stiffness to maximize strength. As a proof of concept, cyanoacrylate-coated sutures were used to perform a clinically relevant flexor digitorum profundus tendon repair in cadaver tissue. Even with this non-ideal adhesive, the maximum load resisted by repaired cadaveric canine flexor tendon increased by ∼ 17.0% compared to standard repairs without adhesive. To rapidly assess adhesive binding to tendon, we additionally developed a lap shear test method using bovine deep digital flexor tendons as the adherends. Further study is needed to develop a strongly adherent, compliant adhesive within the optimal design space described by the model.
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Salehi-Khojin, Amin, and Nader Jalili. "A Shear-Lag Model for Nanotube Reinforced Piezoelectric Polymeric Composites Subjected to Electro-Thermo-Mechanical Loadings." In ASME 2007 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/detc2007-35411.
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Understanding the stress transfer between nanotube reinforcements and surrounding matrix is an important factor in determining the overall mechanical properties of nanotube-reinforced composites. An efficient load transfer from the polymer matrix to the nanotube through interface is required to take the advantage of very high Young’s modulus and strength of carbon nanotubes in the composites. On the other hand, considerable energy dissipation can be obtained by interfacial slippage in the interface of nanotube and matrix which is beneficial in term of structural damping. In order to obtain a composite structure with tunable properties ranges from stiffer structure to better damper, we propose a semi-active control approach. In this method, applied electrical loading to piezoelectric polymeric matrix such as Polyvinylidene Fluoride (PVDF) reinforced with nanomaterials results in radial displacement of piezoelectric polymer corresponding to the direction and magnitude of electrical load. This leads to control of restriction effect of nanotube on the polymer segments, and consequently results in tunable interfacial adhesion between piezoelectric polymer and nanomaterials with faster response time. According to the concept of semi-active control, a shear lag model is obtained for a nanotube reinforced piezoelectric polymer under electro-thermo-mechanical loadings. As the adhesion in carbon nanotube (CNT) composite is universally present in the form of van der Waals interaction, and is the focus of this study, the shear stress and the axial displacement of nanotube and matrix in the interface zone can not be equal. This makes mathematical modeling of interface region more difficult. To solve this complexity, we propose to obtain the relative axial displacement between nanotube and polymer in the interface according to the Lennard-Jones potential function. Results indicate that as the electrical load increases, the relative displacement between nanotube and polymer increases which mean the possibility for slippage increases. Furthermore, results indicate that stiffer structures have more potential to show more switch stiffness capability.
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Zalamea, Luis, Hyonny Kim, and R. Byron Pipes. "Intershell Coupling in Multiwalled Carbon Nanotubes." In CANEUS 2006: MNT for Aerospace Applications. ASMEDC, 2006. http://dx.doi.org/10.1115/caneus2006-11047.
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The interaction and load transfer between multiple shells of a multi-walled carbon nanotube (MWNT) is the subject of intense research by both analysts and experimentalists. Observations of both lubricated sliding and adhesion between the shells of the MWNT have been observed. While the atomic interactions due to simple separation have been successfully modeled by the Lennard-Jones interaction potential for graphene structures, modeling of the shearing deformation mode has been problematic. In the present work, the authors utilize two approaches in continuum mechanics to examine the shearing transfer between shells in a MWNT subjected to extensional and torsional loading wherein the load is transferred through the outer most shell to interior shells. The first approach follows the earlier developments of the authors wherein imperfect bonding between the shells is governed by a shearing transfer efficiency that varies between perfect bonding and frictionless sliding. The second approach utilizes a classical shear lag model to study the shearing transfer between the shells. A comparison between the shear lag and shear transfer models shows the equivalence of the two approaches for two-shell MWNT and numerical solutions are presented for the shear lag model for multiple layers beyond two. Agreement between the two models for multi-shells is demonstrated by varying an adjustable parameter that depends solely on the MWNT geometry. The simplicity of the shear transfer model as compared to the shear lag model constitutes an important advantage. The fundamental discrepancy between the two models lies in the fact that length dependence is inherent to the shear lag analysis, while according to the shear transfer model, stress transfer does not depend explicitly on length.
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Salavatian, M., and L. V. Smith. "Shear Modulus Degradation in Fiber Reinforced Laminates." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-63035.
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Matrix damage, involving transverse and shear cracks, is a common failure mode for composite structures, yet little is known concerning their interaction. A modified Iosipescu coupon is proposed to study the evolution of the shear and transverse damage and their mutual effects. The layup and coupon geometry were selected in a way that controls the severity of the damage and allows the measurement of shear and transverse stiffness degradation directly. The results were compared to material degradation models where damage was dominated by matrix failure. While positive agreement was generally observed in the transverse direction, no model was able to predict the observed shear damage. A new elasticity solution was, therefore, proposed for the shear stress-strain field of a transversely cracked laminate. The approach used a classical shear lag theory with friction applied to the crack surfaces. Using the constitutive relations, the shear modulus reduction was found as a function of crack density, and showed good agreement with experimental measures.