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1
Palla, Leela Prasad. "Blast Response of Composite Sandwich Panels." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1227216480.
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SerraniÌa-Soto, Florencia. "Low velocity impact of composite sandwich panels." Thesis, Queen Mary, University of London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398305.
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Zangani, D. "Modelling of z-Core composite sandwich panels." Thesis, University of Newcastle Upon Tyne, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533691.
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Cowan, Andre James. "Sound Transmission Loss of Composite Sandwich Panels." Thesis, University of Canterbury. Mechanical Engineering, 2013. http://hdl.handle.net/10092/7879.
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This thesis examines the sound transmission loss (STL) through composite sandwich panel systems commonly used in the marine industry. Experimental, predictive and optimisation methods are used to evaluate the acoustic performance of these systems and to improve their acoustic performance with noise treatment.
The complex nature of the material properties of composite sandwich panels was found to be dependent not only on the physical properties but also the frequency of incident noise. Young’s modulus was found to reduce with increasing frequency as has been predicted in the literature which is due to the shear stiffness dominating over the bending stiffness. Two methods for measuring these properties were investigated; ‘fixed-free’ and ‘free-free’ beam boundary condition modal analyses. The disagreement between these methods was identified as the clamping fixed nature that increased flexibility of the beam.
Composite sandwich panels can be modelled as homogeneous isotopic materials when predicting their acoustic performance provided the dilatational resonance is above the frequency range of interest. Two such panels were modelled using this simple sound insulation prediction method, but the agreement between theory and experimental results was poor. A variable Young’s modulus was included in the model but agreement remained relatively poor especially in the coincidence frequency region due to variation of Young’s modulus with frequency.
A statistical method of optimisation of the parameter settings by fractional factorial design proved successful at identifying the important parameters that affect the sound transmission class (STC) of a noise treatment material applied to a panel. The decouple foam layer and attachment method were the most significant factors. The same method, with higher resolution was then used to identify the important parameters that affected the noise reduction class (NRC) finding that the outer foam thickness without a face sheet were the most significant factors. The independent optimisation studies performed for each of the STC and NRC produced conflicting results meaning that both could not be achieved simultaneously.
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Vogler, Tracy J. (Tracy John). "Compressive behavior and failure of composite sandwich panels." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11677.
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Toribio, Michael Garcia-Lopez 1975. "Compressive response of notched composite-honeycomb sandwich panels." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/50540.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1999.Includes bibliographical references (leaves 237-250).
Experimental and numerical work was conducted to understand better the compressive response of notched composite sandwich panels. The quasi-static uniaxial compressive response of notched (circular through hole) E-glass/epoxy- NomexTM sandwich panels were studied experimentally. Two different woven fabric architectures were examined. The key failure mechanism was observed to be linear damage zones (LDZs) emanating from the notch tip (in both materials). LDZ's behaved in a macroscopically similar manner to a bridged crack under tensile loading, and were characterized by semi-stable propagation. Crosssectioning studies revealed the key damage mechanisms operating within the LDZ. Progressive cross-sections indicated that individual fiber microbuckling led to out-of-plane warp tow kinking. The LDZ wake was characterized by kinking in all warp tows and transverse tow splitting. Strain gages were used to measure the in situ damage zone tractions as the LDZ propagated across the width of the specimen; a softening trend was observed. Consistent with observations, a two parameter linear strain softening traction law was used to model the LDZ constitutive behavior. The traction law was treated as a material property. The damage zone modeling (DZM) framework was investigated to determine its validity, specifically its ability to predict three experimentally observed phenomena: the notched strength, local strain distribution, and LDZ growth characteristics. A self-consistent physically-based model should be able to predict all three phenomena. Two models were created in order to interrogate the DZM. The damage growth model was used to determine the ability of the DZM to predict the LDZ growth behavior and notched strength. A finite element model that used discrete nonlinear springs in the wake of the LDZ to model the LDZ as a continuous spring, was implemented to determine if the DZM could predict the local strain distribution. Results showed that the current traction law provided excellent agreement with the phenomenon used to calibrate the traction law, for all specimen sizes. Extension of predictive power to other phenomena resulted in weaker correlations. The modeling framework and methodology established provide a robust tool for investigating the potential of adding physical bases to the DZM.
by Michael Garcia-Lopez Toribio.
S.M.
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Wennhage, Per. "Structural-Acoustic Optimization of Sandwich Panels." Doctoral thesis, Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3161.
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Bambal, Ashish S. "Mechanical evaluation and FE modeling of composite sandwich panels." Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5379.
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Thesis (M.S.)--West Virginia University, 2007.Title from document title page. Document formatted into pages; contains xviii, 141 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 140-141).
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Hanafi, Wemphy. "Flexural performance of glass fiber reinforced composite sandwich panels /." Available to subscribers only, 2007. http://proquest.umi.com/pqdweb?did=1328053201&sid=33&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Tsang, Pui Ho Wilson. "Impact resistance and damage tolerance of composite sandwich panels." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11925.
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Glenn, Christopher Edward. "Fabrication and Structural Performance of Random Wetlay Composite Sandwich Panels." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/43208.
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The random wetlay process is used to make fiber-reinforced thermoplastic sheets that can be compression molded into composite panels at little cost. By utilizing these composite panels as the facesheets of honeycomb sandwich structures, it is possible to greatly increase the bending stiffness of the composite without adding significant weight. The random wetlay composite facesheets used in this research consisted of 25% E-glass fibers and 75% PET by weight. The thickness uniformity of the facesheets was difficult to control. The core of the sandwich structure was HexWeb&174; EM. Three low-cost adhesives were examined for secondarily bonding the facesheets to the core: polyurethane glue; epoxy paste; and 3M Scotch-Grip&174; plastic adhesive. The polyurethane glue mixed with Cab-O-Sil filler was easiest to apply and provided the largest flatwise tensile strength. Mathematical models were developed to predict the static behavior of sandwich beams and plates in bending. Three-point bend tests were performed on a sandwich beam in accordance with ASTM C 393. A sandwich plate simply supported along two opposite edges and free along the other two edges was subjected to a line-load using weights and a wiffle tree arrangement. An effective facesheet modulus and Poissonâ s ratio were found by comparing the measured displacements to the sandwich plate theory. The shadow moiré technique was used to visualize the displacement of the line-loaded sandwich plate. The overall shape of the displacement was very similar to the shape predicted by the sandwich plate theory.Master of Science
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Sirivolu, Dushyanth. "Marine Composite Panels under Blast Loading." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1467993101.
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Kavianiboroujeni, Azam. "Mechanical characterization of wood plastic composite sandwich panels with foam core." Master's thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/26391.
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Tableau d'honneur de la Faculté des études supérieures et postdorales, 2015-2016Le but de ce travail est de produire et de caractériser des structures sandwich à trois couches asymétriques avec ou sans cœur moussé. Pour ce faire, le travail est divisé en deux sections. Dans la première partie, l'effet de la variation des quantités d'agent de couplage et de fibres sont étudiés. La microscopie et la caractérisation mécanique sont utilisées pour évaluer l'effet du polyéthylène greffé d’anhydride maléique (MAPE) sur l'amélioration de la compatibilité entre les fibres de chanvre et le polyéthylène de haute densité (HDPE). Les résultats montrent que les propriétés mécaniques optimales (tension, flexion, torsion et impact) sont obtenues à 9% en poids de MAPE. Dans la deuxième partie, des structures sandwich asymétriques à trois couches, avec ou sans cœur moussé, sont produites par extrusion suivi par un moulage en compression. Les effets de paramètres tels que la densité du cœur, la concentration en chanvre dans les peaux, les épaisseurs des couches et la séquence d'empilage sur leurs comportements en flexion et en impact sont étudiés. Les effets combinés de tous les paramètres mènent à contrôler les propriétés mécaniques (traction, torsion, flexion et impact) des structures sandwich asymétriques.
The aim of this work is to produce and characterize asymmetric three-layer sandwich structures with and without foam core. In order to do so, the work is divided in two sections. In the first part, the effect of coupling agent and fiber content is investigated. Micrographs and mechanical characterizations are used to show that the addition of maleic anhydride polyethylene (MAPE) improved the compatibility between hemp and high density polyethylene (HDPE). It is found that the optimum mechanical properties (tension, flexion, torsion and impact) are obtained with 9% wt. of MAPE in the composite. In the second part, asymmetric three-layer sandwich structures with and without foam core were produced using extrusion followed by compression molding. The effect of different parameters such as core density, skin hemp content, layer thickness, and stacking sequence on their flexural and impact behaviors are studied. The combined effect of all the parameters was found to control the mechanical properties (tension, torsion, flexion and impact) of asymmetric sandwich structures.
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Sirivolu, Dushyanth. "An Analytical Model for High-Velocity Impact of Composite Sandwich Panels." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1227548412.
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Cox, Brandon L. "Full Scale Experimental Testing of Partially Composite Precast Concrete Sandwich Panels." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/6982.
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Precast concrete sandwich panels are a structural system consisting of concrete layers with insulation layers in between. The concrete layers are connected through the insulation with specially designed connectors. For engineers to properly design and analyze the strength characteristics of sandwich panels and their connectors, the engineers need to obtain recommendations from the individual connector manufacturers, which can be a very rigorous process. This project tested eight full scale precast concrete sandwich panels with two concrete layers on either side of an insulation layer with connectors concentrated at either end of each panel. The objectives of this project were to evaluate the interaction between the two concrete layers and how well the connectors transferred forces between the layers (percent of composite action) and to validate simplified methods of predicting properties of the panels by comparing the predicted panel properties to the results of the testing series. Additionally, this study evaluated the panel’s different thicknesses and lengths and compared their results.
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Voth, Christopher Ray. "Lightweight sandwich panels using small-diameter timber wood-strands and recycled newsprint cores." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Fall2009/c_voth_120609.pdf.
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Thesis (M.S. in civil engineering)--Washington State University, December 2009.Title from PDF title page (viewed on Jan. 26, 2010). "Department of Civil and Environmental Engineering." Includes bibliographical references.
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Mano, Jalen Christopher. "Effects of Bio-Composites in Corrugated Sandwich Panels Under Edgewise Compression Loading." DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/2023.
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Present day composite sandwich panels provide incredible strength. Their largest problem, however, is early bonding failure between the core and the skin. This is due to the low bonding surface area of present cores like honeycomb. Corrugated structures could provide a remedy for this with their much larger bonding surface area. Corrugated structures have extreme mechanical properties deeming them particularly useful in aerospace and automotive applications. However, previous research has shown that the stiffness of carbon fiber causes debonding and drastic failure when used as both a core and a skin. Bio-composites have properties that could strengthen the corrugated sandwich panel against such debonding and increase the strength of the structure while making it cheaper and more environmentally friendly.
This thesis presents the optimum design, manufacturing, and testing of corrugated sandwich panel structures with integrated bio-composites under edgewise compression loading. To do this, optimum corrugation geometry was identified using theoretical analysis of the moment and bonding area of the shape. Control tests with carbon fiber and hemp were conducted. The bio-composite was integrated in both the core and the skin individually in corrugated sandwich panels. The cases tested were all-carbon fiber, hemp skin with carbon fiber core, carbon fiber skin with hemp core, and all-hemp. These corrugated structures were analyzed by conducting compression loading tests on varying lengths of single-ligament panels utilizing trapezoidal corrugation as the core and a flat plate as the skin. The lengths tested were 1, 2, 3, and 4 inches. As many samples as possible were manufactured out of limited material with heavier focus on creating the shorter samples. The goal of this testing was, first, to determine if hemp fibers were viable as a substitute for certain sections of the traditional composite structure, and second, to see if integrating hemp fibers would solve the problems of debonding seen in the all-carbon fiber samples seen in previous research. To determine mechanical property viability, the ultimate load and stiffness were investigated for each sample, as well as investigation of the failure modes seen in the test. Secondary goals were to see at what length buckling behavior became an issue and to see if this corrugated structure and all its failure modes could be simulated in finite element analysis.
At the 1-inch and 2-inch lengths where minimal buckling was encountered, the hemp core-carbon skin samples showed better results than both the all-carbon fiber and the all-hemp samples with a 4% and 6% increase in average ultimate load and a 11% and 47% increase in stiffness, respectively. From these results, it was concluded that hybrid bio-composite structures can have comparable mechanical properties to traditional composites and can solve bonding failure.
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Chapagain, Pradeep. "Dynamic Response of Foam-Core Composite Sandwich Panels Under Pressure Pulse Loading." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1311707991.
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Ramroth, William T. "Thermo-mechanical structural modelling of FRP composite sandwich panels exposed to fire." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3232967.
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Thesis (Ph. D.)--University of California, San Diego, 2006.Title from first page of PDF file (viewed December 1, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 155-161).
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Barreiro, Jose. "Blast Resistance of Non-Composite Tilt-Up Sandwich Panels and their Connections"." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34291.
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Blast risk associated with terrorist threats and accidental explosions has become an international concern over the past decade and has provoked structural engineers to implement protective design measures. Recent advances in this area of research has seen tremendous improvements in mitigating this risk through the installation of retrofits, advanced structural design, or pre-emptive protective measures. Tilt-up and precast panel walls are constructed using a unique approach in which the walls are cast horizontally and lifted, or tilted, into their final vertical position. These unique structures are cost effective, energy efficient, and can be rapidly constructed. This approach is commonly applied to the construction of large industrial facilities and the construction of schools which are categorized as high importance structures in the National Building Code of Canada. These panels are inherently flexible and have a surplus of mass making them desirable for protective design applications, however their behaviour under blast induced loads is not well defined.
This experimental research project investigates the behaviour of non-composite tilt-up sandwich (NCTS) panels and solid reinforced concrete (SRC) panels with realistic support conditions subjected to blast-induced shockwaves. Previous research shows that NCTS panels, identifiable by their large structural wythe, exhibit some degree of composite behaviour and require between 5% to 10% composite action for successful erection.
Five scaled specimens were constructed following common procedures used in practice, equipped with identical data acquisition instruments, and tested at the University of Ottawa shock tube testing facility under similar blast pressure-impulse combinations. Test results for the NCTS and SRC panels are compared graphically in terms of displacement–time histories and sectional strain distributions. The data is evaluated to approximate the composite behaviour at mid-span of the NCTS panel. Analytical results generated, using “RC Blast,” single-degree-of-freedom analysis software developed at the University of Ottawa, were validated with empirical data and are presented graphically.
Each specimen was equipped with connections similar to those commonly used in the construction of NCTS panels. These connections were experimentally studied under simulated blast pressures and analysed using CSA A23.3-04 guidelines for punching shear capacity. Modified support
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reinforcement layouts and surface bonded FRP laminates were evaluated as strengthening and retrofit techniques to prevent support failure. Dynamic support reactions and predicted support resistances are tabulated for each shot of every panel.
The results indicate that it is possible to accurately predict the flexural behaviour and support resistance of a NCTS panel using RC Blast and CSA A23.3-04 guidelines. Several factors considered in this analysis include boundary conditions, dynamic material properties, and shear tie degradation. This analysis of flexural behaviour is highly dependent on shear stiffness, which is directly related to the composite action within NCTS panels. Support resistance was increased significantly through application of the strengthening techniques outlined in this thesis.
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Zhao, Huyue. "Stress Analysis of Tapered Sandwich Panels with Isotropic or Laminated Composite Facings." Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/ZhaoH2002.pdf.
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Evans, Thomas H. "Design of composite sandwich panels for lightweight applications in heavy vehicle systems." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4745.
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Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains ix, 125 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 124-125).
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Thomas, Anton F. (Anton Felipe) 1977. "Anomaly edge effects in thermographic nondestructive testing of polymeric composite sandwich panels." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/89365.
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Motipalli, V. V. Satish K. "Reduction of vibration transmission and flexural wave propagation in composite sandwich panels." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/18973.
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Doctor of PhilosophyDepartment of Mechanical and Nuclear Engineering
Liang-Wu Cai
X. J. Xin
Thin walled structures such as plates and shells have application in many fields of engineering because these structures are light weight and can support large loads when designed suitably. In real world, loads may cause these structures to vibrate which can be undesirable causing fatigue and failure of the structure. Such undesirable vibrations need to be reduced or eliminated. In this work, analytical studies of flexural wave propagation for idealized geometries are conducted and finite element method (FEM) is used to explore the effects of composite panel designs of finite size for the reduction of vibration transmission. In the analytical studies, the influence of the material properties on the reflection and transmission characteristics are explored for an infinite bi-material plate, and infinite plate with a strip inhomogeneity. In the analytical study of an infinite thin plate with a solid circular inclusion, the far and near field scattering characteristics are explored for different frequencies and material properties. All the analytical studies presented here and reported in the literature consider infinite plates to characterize the flexural wave propagation. Obtaining closed form solutions to characterize the flexural wave propagation in a finite plate with inclusions is mathematically difficult process. So, FEM is used to explore the composite panel designs. The understanding gained about the material properties influence on the flexural wave propagation from analytical studies helped with the choice of materials for FEM simulations. The concept of phononic crystals is applied to define the design variations that are effective in suppressing vibration transmission. Various design configurations are explored to study the effects of various parameters like scatterer’s material properties, geometry and spatial pattern. Based on the knowledge gained through a systematic parametric study, a final design of the composite sandwich panel is proposed with an optimum set of parameters to achieve the best vibration reduction. This is the first study focused on reducing vibration and wave transmission in composite rotorcraft fuselage panels incorporating the concept of phononic crystals. The optimum sandwich panel design achieved 98% vibration transmission reduction at the frequency of interest of 3000 Hz.
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James, Chris T. "Numerical modelling of the compression-after-impact behaviour of composite sandwich panels." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/17994.
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Sandwich panels using fibre-reinforced composite skins and low-density cores are being increasingly used in the aerospace industry due to their superior specific strength and stiffness, and increased design flexibility over traditional metallic and composite structures. However, it is well-known that sandwich panels are highly vulnerable to the effects of impact damage, with even low-energy impacts potentially causing very severe reductions in the in-plane compressive strength of these structures. The objective of this project was to produce a faithful and reliable numerical model for the simulation of the compression-after-impact strength of composite sandwich panels. An in-depth literature review revealed that delamination within the skins of a sandwich panel is a damage mechanism that has gone almost entirely neglected in previous efforts at modelling this problem, despite the proven significance of this mechanism in the failure of impact damaged sandwich panels in compression. Consequently, the use of the cohesive zone model for delamination initiation and propagation is the key unique feature of this model, with Hashin s criteria being used for intra-laminar damage formation, and a simple plasticity response capturing core crushing. An experimental study is performed to produce a thorough dataset for model validation, featuring differing levels of damage induced via quasi-static indentation, and novel asymmetric panels with skins of unequal thickness (the thinner skin being on the unimpacted side). The experimental study revealed that the use of a thinner distal (undamaged) skin could improve the strength of mildly damaged sandwich panels over undamaged sandwich panels using the same asymmetric configuration. It is believed that this effect is due to the movement of the neutral plane of the sandwich panel caused by the reduction in the stability of the damaged skin through stiffness reduction and geometric imperfections. This removes the eccentricity of the compressive loading that exists in the undamaged asymmetric panels, which has mismatched axial stiffness between the indented skin and the thinner distal skin, and thus a noticeably lower ultimate strength than the undamaged symmetric panels. The sandwich model is developed using pre-existing experimental and material data, and trialled for a variety of different skin lay-ups, core thicknesses and indenter sizes. The numerical model generally agreed well with the ultimate stress found in the experiments for these different configurations, but is quite poor at estimating the magnitude of the damage induced by the indentation. When used to model the experimental study, the model gave generally good, conservative estimates for the residual compressive strength of both the symmetric and asymmetric panels. The tendency of the asymmetric panels to become stronger with mild damage was not captured by the model per se, with the numerical results instead showing an insensitivity to damage in the asymmetric panels, which was not shared by the symmetric panels. However, the numerical model did exhibit erroneous strain-stress responses for both panel configurations, particularly for the undamaged and mildly damaged cases. Investigations revealed that this erroneous behaviour was caused by inconsistency in the material data, which had been collected partially via experimentation and partly from literature sources. Overall, the model developed here represents a promising advancement over previous efforts, but further development is required to provide accurate damage states.
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Sandoval, Robee Ybañez. "Comparative analysis of single-wythe, non-composite double-wythe, and composite double-wythe tilt-up panels." Kansas State University, 2017. http://hdl.handle.net/2097/35460.
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Master of ScienceDepartment of Architectural Engineering and Construction Science
Kimberly Waggle Kramer
Insulated precast concrete sandwich panels are commonly used for exterior cladding on a building. In recent years, insulated tilt-up concrete sandwich panels are being used for the exterior load-bearing walls on a building. The insulation is sandwiched between exterior and interior concrete layers to reduce the heating and cooling costs for the structure. The panels can be designed as composite, partially composite, or non-composite. The shear ties are used to achieve these varying degrees of composite action between the concrete layers. A parametric study analyzing the standard, solid single-wythe tilt-up concrete wall panel and solid sandwich (double-wythe separated by rigid insulation) tilt-up concrete wall panels subjected to eccentric axial loads and out-of-plane seismic loads is presented. The sandwich tilt-up panel is divided into two categories – non-composite and composite wall panels. The height and width of the different types of tilt-up wall panel is 23 feet (21 feet plus 2-foot parapet) and 16 feet, respectively. The solid standard panel (non-sandwich) is 5.5 inches in thickness; the non-composite sandwich panel is composed of 3.5-inch architectural wythe, 2.5-inch rigid insulation, and 5.5-inch interior load bearing concrete wythe; and the composite sandwich panel is composed of 3.5-inch exterior, load bearing concrete wythe, 2.5-inch insulation, and 5.5-inch interior, load bearing concrete wythe. The procedure used to design the tilt-up wall panels is the Alternative Method for Out-of-Plane Slender Wall Analysis per Section 11.8 of ACI 318-14 Building Code Requirements for Structural Concrete and Commentary. The results indicated that for the given panels, the applied ultimate moment and design moment strength is the greatest for the composite sandwich tilt-up concrete panel. The standard tilt-up concrete panel exhibits the greatest service load deflection. The non-composite sandwich tilt-up concrete panel induced the greatest vertical stress. Additionally, the additional requirements regarding forming materials, casting, and crane capacity is covered in this report. Lastly, the energy efficiency due to the heat loss and heat gain of sandwich panels is briefly discussed in this report. The sandwich tilt-up panels exhibit greater energy efficiency than standard tilt-up panels with or without insulation.
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Melrose, Paul Thomas. "Elastic Properties of Sandwich Composite Panels Using 3-D Digital Image Correlation with the Hydromat Test System." Fogler Library, University of Maine, 2004. http://www.library.umaine.edu/theses/pdf/MelrosePT2004.pdf.
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Helmstetter, Dennis J. "Analysis procedures for optimizing the core of composite sandwich panels for blast resistance." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 165 p, 2009. http://proquest.umi.com/pqdweb?did=1885754601&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Worrall, Christopher Michael. "The behaviour of composite sandwich beams and panels under low velocity impact conditions." Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333578.
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Grigg, William Reid. "Post-Injection Welded Joint Fatigue Tests of Sandwich Plate System Panels." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/44900.
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The Sandwich Plate System (SPS) is created by bonding two steel plates together with an elastomer core that is injected into a cavity formed by the steel plates and perimeter bars. The result is a stiffer and lighter panel that can be used for plate-like structures such as bridge decks, stadium risers or ship decks. For more versatility, the effects of welding post-injection to the SPS panels were investigated.
Three post-injection welded joints were tested to determine fatigue resistance and the effects of cyclic loading on the localized debonding of the heat affected zone at the post-injection welded joint of a SPS bridge deck. Seven panels containing one of three post-injection weld configurations were investigated. Each panel was fatigue tested to ten million cycles or until failure, by applying remote bending to the post-injection welded joint.
Experimental deflections and strains were compared to finite element analyses. Fatigue-life predictions were made using code based S-N curves, and a relatively new mesh-insensitive structural stress method with a master S-N curve approach.
The post-injection welded joint demonstrated good fatigue resistance to recommended AASHTO loading when shims were used under the middle support to offset the camber in the SPS panels. It was also found that stresses caused by draw down of the camber had an adverse affect on the post-injection welded joint and greatly reduced its fatigue resistance.Master of Science
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Gao, Yifei. "Response of Curved Composite Panels under External Blast." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1404084105.
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Nash, Peter. "Experimental impact damage resistance and tolerance study of symmetrical and unsymmetrical composite sandwich panels." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/21748.
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This thesis presents the work of an experimental investigation into the impact damage resistance and damage tolerance for symmetrical and unsymmetrical composite honeycomb sandwich panels through in-plane compression. The primary aim of this research is to examine the impact damage resistance of various types of primarily carbon/epoxy skinned sandwich panels with varying skin thickness, skin lay-up, skin material, sandwich asymmetry and core density and investigate the residual in-plane compressive strengths of these panels with a specific focus on how the core of the sandwich contributes to the in-plane compressive behaviour. This aim is supported by four specifically constructed preconditions introduced into panels to provide an additional physical insight into the loading-bearing compression mechanisms. Impact damage was introduced into the panels over a range of IKEs via an instrumented drop-weight impact test rig with a hemi-spherical nosed impactor. The damage resistance in terms of the onset and propagation of various dominant damage mechanisms was characterised using damage extent in both impacted skin and core, absorbed energy and dent depth. Primary damage mechanisms were found to be impacted skin delamination and core crushing, regardless of skin and core combinations and at high energies, the impacted skin was fractured. In rare cases, interfacial skin/core debonding was found to occur. Significant increases in damage resistance were observed when skin thickness and core density were increased. The reduction trends of the residual in-plane compressive strengths of all the panels were evaluated using IKE, delamination and crushed core extents and dent depth. The majority of impact damaged panels were found to fail in the mid-section and suffered an initial decline in their residual compressive strengths. Thicker skinned and higher density core panels maintained their residual strength over a larger impact energy range. Final CAI strength reductions were observed in all panels when fibre fracture in the impacted skin was present after impact. Thinner skinned panels had a greater compressive strength over the thicker skinned panels, and panel asymmetry in thin symmetrical panels appeared to result in an improving damage tolerance trend as IKE was increased due to that the impact damage balanced the in-plane compressive resistance in the skins with respect to the pre-existing neutral plane shift due to the uneven skin thickness.
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Taylor, Matthew Claire. "Damage tolerance of composite honeycomb sandwich panels under quasi-static bending and cyclic compression." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/41237.
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Orlowski, Michal. "Experimental and numerical investigation on the bird impact resistance of novel composite sandwich panels." Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/9573.
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Bird strikes represent a major hazard to the aerospace composite structures, due to their low impact resistance. Accurate selection and lay up of the materials in the composite structure can significantly improve the out of plane properties of the composites. However, application of the complex hybrid sandwich composites into bird strike proof structures was not investigated yet. Therefore, this work was focused on the soft body impact resistance of a novel composite design for aerospace applications. The investigation was divided into experimental and modelling parts. In the beginning of this thesis, the numerical techniques for modelling of bird im¬pact and composite materials were studied. The theoretical background for the corresponding issue was provided, followed by the thorough validation of the exist¬ing numerical approaches. A Smooth Particle Hydrodynamic (SPH) method was chosen for the modelling of the soft body. This modelling technique was validated against experimental data for the rotating fan blade. Three parametric studies of bird impacting fan blades revealed strong influence of the bird impact location and timing on the final deformed shape of the blade. Moreover, it was proved that the SPH is capable of reproducing the exact load on the structure and is appropriate technique for modelling bird strikes.
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Fuller, L. Bryant. "Damage and compressive failure of unbalanced sandwich composite panels subject of a low-velocity impact." Monterey, California. Naval Postgraduate School, 1994. http://hdl.handle.net/10945/30855.
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Woo, Thomas Robert. "Effects of Seawater on the Mechanical Behavior of Composite Sandwich Panels Under Monotonic Shear Loading." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/898.
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Abstract
Salt water environments are very harsh on materials that are used within them. Many issues are caused by either corrosion and/or internal degradation to the materials themselves. Composites are better suited for this environment due to their high strength to weight ratios and their corrosion resistance, but very little is known about the fracture mechanics of composites. The goal of this study is to gain a better understanding for the behavior of a composite boat hull under a shear loading, similar to the force water applies on the hull as the boat moves through the water; then attempt to strengthen the composite sandwich panel against the shear loading.
A parametric study was conducted to investigate monotonic in-plane shear loading for composite sandwich panels used in commercial naval vessels. In order to model a conventional composite boat hull, test specimens were composite sandwich panels made of a Divinycell H100 foam core with four layers of fiberglass on both sides of the core. Specimens were tested under a monotonic loading with a rate of 0.2 in/min, and tested until complete failure using the standard test.
Seawater specimens were manufactured in the same manner as the original test specimens, but then were submersed in either filtered seawater or the ocean. The differences between the filtered pieces and the ocean allowed us to determine if any changes found in the composite sandwich panels were related to environment conditions or if the changes were related to the saltwater interaction itself. To create these different environments the seawater specimens were taken to the Avila pier where 36 specimens were placed in a tub that was fed filtered saltwater, while 30 specimens were placed in a plastic mesh with weights and lowered to a depth of approximately 30 ft. in the ocean. Three specimens were then removed at monthly intervals from both filtered and ocean environments.
Shear Keys were created as a method to strengthen the composite sandwich panels against the shear force that the previous specimens had been tested to. Eight Shear Keys were then placed into groves cut into the foam core (four on each side) and the four fiberglass layers were laid on top.
Testing showed that the seawater did have an initial effect on the composite sandwich panels. The filtered pieces showed a decrease in yield strength and stiffness the longer they were subjected to the seawater. The raw unfiltered pieces placed in the ocean saw an even higher decrease in their yield strength and decrease in stiffness. However, for both the unfiltered and raw specimens there was an increase in the ultimate strength and fracture point of the specimens. The effects of the sea water seemed to taper off after the 3rd month however.
The Shear Key specimens were tested with a 4mm and an 8mm Shear Key. The 8mm Shear Keys showed a decrease in shear strength, which was primarily due to removing too much material from the core and weakening the specimen. It was concluded that the decrease in area created a force concentration at the deepest part of the Shear Key causing the premature failure. The 4mm Shear Key showed an increase in the yield strength, ultimate strength, and fracture point. A finite model was built to simulate the original test specimen along with the 4mm and 8mm Shear Key cases, and the results were compared to the experimental results.
The numerical results showed that it was possible to relate the experimental results to the linear or elastic portion of the plots. There was a difference between the maximum displacement of the model and the actual specimens, but this was attributed to potential inaccurate comparison of the loading on the model compared to the actual specimens. The correlation between the model itself and the experimental data was close enough to conclude that it could be used for predicting baseline trends.
Further investigation of the specimens should include looking into the effects of a cyclic shear loading on the specimens. This combined with the seawater element used in this thesis would provide further insight to the initial degradation seen in the seawater specimens, and could potentially provide a closer relation to current hull failures. In addition to including a cyclic loading another numerical model should be created. A model that could be constrained both locally and globally would provide more accurate results. The FEM should also include the ability to run a crushable foam core model within the solver which would also increase the accuracy of the numerical solution.
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Hill, Michelle Denise. "Damage resistance and tolerance investigation of carbon/epoxy skinned honeycomb sandwich panels." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/10072.
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This thesis documents the findings of a three year experimental investigation into the impact damage resistance and damage tolerance of composite honeycomb sandwich panels. The primary area of work focuses on the performance of sandwich panels under quasi-static and low-velocity impact loading with hemispherical and flat-ended indenters. The damage resistance is characterised in terms of damage mechanisms and energy absorption. The effects of varying the skin and core materials, skin thickness, core density, panel boundary conditions and indenter shape on the transverse strength and energy absorption of a sandwich panel have been examined. Damage mechanisms are found to include delamination of the impacted skin, core crushing, limited skin-core de bonding and top skin fibre fracture at high loads. In terms of panel construction the skin thickness is found to dominate the panel strength and energy absorption with core density having a lesser influence. Of the external factors considered the indenter noseshape has the largest effect on both failure load and associated damage area. An overview of existing analytical prediction methods is also included and the most significant theories applied and compared with the experimental results from this study. The secondary area of work expands the understanding obtained from the damage resistance study and assesses the ability of a sandwich panel to withstand in-plane compressive loading after sustaining low-velocity impact damage. The importance of the core material is investigated by comparing the compression-after-impact strength of both monolithic carbon-fibre laminates and sandwich panels with either an aluminium or nomex honeycomb core. The in-plane compressive strength of an 8 ply skinned honeycomb sandwich panel is found to be double that of a 16 ply monolithic laminate, with the type of honeycomb also influencing the compressive failure mechanisms and residual compressive strength. It is concluded that under in-plane loading the stabilising effect of the core opposes the de-stabilising effect of any impact damage.
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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.
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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.
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Sinclair, Gregory Maurice. "The response of singly curved fibre reinforced sandwich and laminate composite panels subjected to localised blast loads." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13328.
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Includes bibliographical references.This report presents results from a study on the response of singly curved fibre reinforced polymer (FRP) sandwich and laminate panels subjected to localised blast loads. The aim of the project was to investigate and compare the blast mitigation potential of each panel type and the influence of curvature on the response. Three radii of curvature were examined for both panel types, namely infinite (flat), 1000mm and 500mm. The FRP laminate panels were designed to consist of 1-5 layers of Eglass fibre reinforced epoxy sheets. The FRP sandwich panels consisted of a PVC foam core with 6 layers of FRP sheets on either side. Vacuum infusion, with the aid of three moulds, was used to manufacture the panels. The average thicknesses and areal densities of the FRP sandwich and laminate panels were 18.7mm and 4.9mm; and 862-8g/1m2 and 8458-g/m2 respectively. Three point quasi-static flexural tests were conducted on FRP sandwich and laminate specimens where the localised compression failure beneath the central loading bar was evident on both types of structures. The presence of the core reduced the damage observed on the back face of the FRP sandwich specimens. Blast tests were conducted on a horizontal ballistic pendulum at the Blast Impact and Survivability Research Unit (BISRU), University of Cape Town. Localised blasts were generated by detonating circular cylinder PE4 plastic explosives, placed at a constant standoff distance of 10mm. The charge mass ranged from 10g to 32.5g across all the panels. The failure modes of the blast loaded panels were identified by a post-test inspection. The failure mode initiation charts for the F RP sandwich panels revealed that failure modes were initially observed on the front face sheet and core material with slight appearance of delamination on the back face sheet. Increasing the charge mass resulted in the rupture of the front face sheet and penetration of the core. Additional failure of the back face sheet was also evident as the charge mass increased. The failure mode initiation charts of the FRP laminate panels exhibited less severe failure modes across a greater charge mass range that eventually lead to complete fibre rupture at higher charge masses. Delamination of the front face sheet of the flat FRP sandwich panels was initially observed in the centre of the panel and spread into the exterior region for increasing charge mass. The failure of the core material initially reduced the delaminated area of the back face sheet, however once the rupture of the front face sheet occurred, the delaminated area of the front face sheet reduced and the delaminated area of the back face sheet increased. This was similar for the curved FRP sandwich panels except that the delaminated area was predominately parallel to the axis of curvature prior to rupture and perpendicular to the axis of curvature subsequent to rupture. Delamination in the flat FRP laminate panels was initially observed in the centre of the panel and along the clamped boundary. Increasing charge mass resulted in the delaminated region spreading across the panel. As with the FRP sandwich panels, the delaminated area of the curved FRP laminate panels was initially observed parallel to the axis of curvature prior to rupture. Debonding of the FRP sandwich panels was initially observed at both of the front and back interfaces. For the front interface, the debonded lengths were observed in the centre and in exterior test area of the panel, but only in exterior test area for the back interface. With the rupture of the front face sheet, the debonded length of the front interface decreased and the back interface increased and spread across the entire test area. The blast rupture threshold of the two panel types were compared in terms of largest charge mass resisted. For each radii category, the FRP laminate panels outperformed the FRP sandwich panels, namely by 5g for the flat panels (25g vs 20g) and 9g for the 1000mm curved panels (27.5g vs 18.5g). However, for the 500mm curved panels the FRP laminate and sandwich panels ruptured at identical charge masses of 27.5g.
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Ghoor, Ismail B. "The response of concave singly curved fibre reinforced moulded sandwich and laminated composite panels to blast loading." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/27811.
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Composite materials are increasingly being used in a wide range of structural applications. These applications range from bicycle frames and building facades to hulls of marine ships. Their popularity is due to the high specific strength and stiffness properties, corrosion resistance, and the ability to tailor their properties to a required application. With the increasing use of composites, there is a need to better understand the material and damage behaviour of these structures. In recent years, the increased frequency of wars and terror attacks have prompted investigations into composite failure processes resulting from air-blast. Most of the research has been focused on flat panels, whereas there is relatively little on curved structures. This dissertation reports on the effect of air-blast loading on concave, singly curved fibre reinforced sandwich and composite panels. Sandwich panels and equivalent mass glass fibre laminates were manufactured and tested. Three types of curvature namely a flat panel (with infinite curvature), a curvature of 1000 mm radius and a curvature of 500 mm radius were produced, to determine the influence of curvature on panel response. The laminates were made from 16 layers of 400 g/m² plain weave glass fibre infused with Prime 20 LV epoxy resin. The sandwich panels consisted of a 15 mm thick Airex C70:75 core sandwiched between the 12 layers of 400 g/m² plain weave glass fibre and infused with Prime 20 LV epoxy resin. This arrangement produced a balanced sandwich panel with 6 layers of glass fibre on the front and back respectively. For all panels, vacuum infusion was used to manufacture in a single shot process. Mechanical properties of samples were tested for consistency in manufacturing. It was found that mechanical properties of the samples tested were consistent with low standard deviations on tensile and flexural strength. The panels were tested in the blast chamber flat the University of Cape Town. Blast specimens were clamped onto a pendulum to facilitate impulse measurement. Discs of plastic explosive, with charge masses ranging from 10 g to 25 g, were detonated. After blast testing, a post-mortem analysis of the damaged panels was conducted. Post-mortem analysis revealed that the failure progression was the same irrespective of curvature for both the sandwich panels and the laminates. Sandwich panels exhibited the following failure progression: delamination, matrix failure, core crushing, core shear, core fragmentation, core penetration and fibre fracture. The laminates displayed the following progression: delamination, matrix failure and fibre fracture. Curved panels exhibited failure initiation at lower charge masses than the flat panels. As the curvature increased, the failure modes initiated at lower charge masses. For example, as the charge mass was increased to 12.5 g the front face sheets of the flat and the 1000 mm radius sandwich panels exhibited fibre fracture, but the 500 mm radius sandwich panel exhibited fibre fracture and rupture through the thickness of the front face sheet. The 500 mm radius laminate exhibited front face failure earlier (15 g) than the 1000 mm radius (22.5 g) and flat panel (20 g). Curved laminates exhibited a favoured delamination pattern along the curved edges of the panel for both 1000 mm and 500 mm radii laminates. As the curvature increased, more delamination was evident on the curved edges. The curved panels displayed more severe damage than flat panels at identical charge masses. Curved sandwich panels experienced through thickness rupture at 20 g charge mass whereas the curved laminates did not exhibit rupture at 25 g charge mass. The flat laminates were the most blast resistant, showing no through-thickness penetration at 25 g (the highest charge mass tested) and initiated failure modes at higher charge masses when compared to the other configurations.
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Tafoya, Justin A. "Effect of Sustainable and Composite Materials on the Mechanical Behavior of Sandwich Panels under Edgewise Compressive Loading." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1362.
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Over the last three decades, the aerospace industry has gradually shifted from metals to composites in many different applications due to the lightweight properties of composite materials. Some benefits of composites include higher strength-to-weight ratio and corrosion resistance. At this point in time, the composite industry researchers are focusing on renewable and sustainable materials (bio-composites). By understanding the structural capabilities of bio-composites that have been used for centuries, new developments of sustainable materials will spark more interest throughout the industry. Bio-composites include fibers such as hemp, bamboo, flax, etc. The high demand for bio-composites in composite structures can also reduce raw material costs.
This study investigated, through experimental and numerical analysis, the mechanical behavior of sandwich panels under edgewise compressive loading. The first task of the study was to use four different facesheet materials and the same Nomex honeycomb core. The number of facesheet layers consecutively increased from one layer to four layers on each side of the core for each material. The facesheet materials used were Hexply AGP280-5H Carbon Fiber Pre-Preg, B601 Plain Weave Hemp, D118DKBR Split Herringbone Weave Hemp, and NB308T 7725 Texalium Fiberglass Pre-Preg. The sandwich panels were cured using a composite heat press and followed the recommended cure cycle for the material’s resin matrix. The variation of the facesheet materials while keeping the core consistent showed how the edgewise strength and displacement of the composite sandwiches were affected under compressive loading. The second task of the study was to try and create a multifunctional hybrid composite sandwich with two different facesheet materials; using one hemp material and one pre-preg material. The goal of this task was to try and minimize the damage occured upon failure. Being that the pre-preg materials are more brittle than the hemp material, the hybrid composite sandwiches can potentially create a superior composite structure. The sequence of stacking of the facesheet materials was manipulated to study how changing the outer and inner layers affected the results. All the specimen were loaded at a rate of 0.05 in/min in a steel jig specifically made per ASTM C364 standard using an Instron 8801 to determine the mechanical behavior. These experimental results combined with results from theoretical and finite element analysis using Matlab and Abaqus, respectively, were used to compare composite sandwich designs under compressive loadings. Failure mode comparison between the individual material composites and the hybrid composites were also discussed.
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Wennberg, David. "Multi-Functional Composite Design Concepts for Rail Vehicle Car Bodies." Doctoral thesis, KTH, Järnvägsgruppen, JVG, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122391.
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Structures and material combinations, tailored for multiple purposes, are within the reach of vehicle manufacturers. Besides reducing the environmental impact of the transportation sector these multi-functional structures can reduce costs, such as development, manufacturing and maintenance, and at the same time offer improved comfort to the passengers. This thesis sets out to develop multi-functional design algorithms and evaluate concepts for future composite high speed train car bodies with the objective of optimising the amount of mass needed to fulfil all functions of the structure. In a first step complete composite car bodies were developed, optimised and evaluated based on global stiffness requirements and load cases. The knowledge gained in this step was used as requirements for the strength and stiffness of panels during the continued development of the multi-functional optimisation which, besides strength and stiffness, later also considers sound transmission, thermal insulation, geometric restrictions, manufacturability and fire safety. To be able to include fire safety in the analysis, a method for simulating the high temperature response of layered composite structures was needed, and developed. Significant weight reductions are proven when utilising carbon fibre in the load carrying structure of the vehicle, on component level as high as 60%. Structures can be made significantly thinner when using the algorithms developed in this thesis and wall thickness is reduced by 5-6 cm. Analysis carried out and extensive literature surveys also suggest significant cost savings in manufacturing, maintenance and use-phase, even thou the raw material cost can be significantly higher as compared to the conventional steel or aluminium alternatives. Results from drive cycle simulations showed that the benefit, with respect to reduced energy consumption, is in the range of 0.5-0.8% per reduced weight percentage, comparable to both automotive and air applications. The algorithms and methods established in this thesis can be directly applied for the development and analysis of future high speed train car bodies.QC 20130521
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Francis, Philip. "The influence of shear connection strength and stiffness on the resistance of steel-concrete composite sandwich panels to out-of-plane forces." Thesis, University of Surrey, 2018. http://epubs.surrey.ac.uk/848767/.
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Steel-concrete-steel (SCS) sandwich panels are an efficient means of achieving a strong and stable composite wall. Development in the 70's and 80's focussed on tunnelling, with other applications, particularly in the defence and offshore sectors, appearing later. Renewed focus has been placed on the system in recent years due to a proliferation of proposals for new nuclear power stations in Europe. Many new nuclear projects that have been completed in recent years have been significantly delayed by problems with reinforcement congestion. SCS construction offers a potential solution to this, since reinforcement is either significantly reduced or eliminated entirely in most designs. As a result of this renewed interest, industry has sought to develop improved design rules, both for economy and easier regulatory approval. As with any composite system, the strength of the system is derived from the ability of the materials to interface efficiently with each other where they are connected. Review of existing design guides and research showed a gap in understanding of the effects of shear connection on the overall behaviour of the system, particularly when resisting out-of-plane loads. This thesis aims to improve this understanding, leading to improved design provision and a wider range of applications for SCS panels in industry. An extensive literature search found a large body of test results. However, the majority of these tests are for designs where shear connection is over-provisioned, meaning shear connection is not critical. The tests that were conducted with lower degrees of shear connection were found to be insufficient to draw definitive conclusions about changes in behaviour. For this reason, numerical modelling using finite element analysis was used to supplement the test data. A validation and verification exercise was performed, which showed that the model accurately predicted the behaviour seen in testing, for all of the relevant failure modes. This thesis focusses on the three design checks that are required for panels subject to out-of-plane loads; bending resistance, shear resistance and deflection. The effect of reduced shear connection on each of these design checks is explored in turn. For bending resistance, design rules based on first principles cross-section equilibrium are found to accurately predict the point of failure for the majority of cases. However, the existing assumption of a smooth profile of shear connector force is found to be incorrect on the tension plate, with tensile cracking leading to discontinuities in the stud force profile. Further interpretation of this result shows that this can lead to an unconservative prediction of the failure load when a panel with a low degree of shear connection is subject to a uniformly-distributed load (UDL). A new design rule is presented for this situation. Design equations for shear resistance are found to vary considerably between design codes and countries. As with the bending check, the test database is found to be lacking in tests with low enough degrees of shear connection to draw definitive conclusions about any changes in behaviour. A parametric FE study is presented to investigate these effects. The study focusses on varying the degree of shear connection for groups of beams loaded at different shear-span to depth ratios. Different behaviour is observed in each group, with the influence of shear connection varying, depending on which shear transfer action is dominant. The study shows that unconservative predictions are made for a number of the design models, particularly for slender beams with low degrees of shear connection. A new adjustment is presented for the Eurocode shear resistance model that removes the unconservative predictions. The models from the fib Model Code are suggested as a better alternative, again with some adjustment to account for reduced degree of shear connection. Deflection of SCS panels is usually predicted using linear-elastic models. Debate has occurred about whether to base the stiffness used on the contribution of the steel plates only, or whether the concrete stiffness should be included. This work finds that a partial concrete contribution should be assumed. It is also found that simple bending prediction models, based on Euler-Bernoulli principles, tend to overestimate stiffness for beams with low shear-span to depth ratios. In these cases, models that include shear deformation (such as the model by Timoshenko) are found to produce more accurate predictions. Reduced shear connection is found to lead to non-linear load deflection response curves, which cannot be easily approximated with linear-elastic models. A new load-stiffness curve is proposed for simplified non-linear modelling, which could be easily implemented in most current software packages with non-linear solvers. Finally, partial resistance factors for the bending and shear design checks are calculated, using the procedure presented in Annex D of Eurocode 0. This method takes into account the precision and conservativeness of a particular design equation through a systematic comparison with available test data, and penalises studies that are based on limited test data. The procedure is found to be deficient when the design model includes contributions from multiple materials and large numbers of parameters. To overcome this, a novel extension to the existing procedure is proposed, termed the 'matrix method'. In general, it is concluded that lower degrees of shear connection are not immediately detrimental to the performance of the system. This thesis highlights the changes in behaviour that can occur, which designers should account for when calculating the resistance of panels. This thesis also presents new adjustments and design rules to allow resistance to be accurately calculated in such cases.
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Verstappen, André Paul. "Passive damping treatments for controlling vibration in isotropic and orthotropic structural materials." Thesis, University of Canterbury. Mechanical Engineering, 2015. http://hdl.handle.net/10092/10197.
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The structural vibration damping behaviour of plates and beams can be improved by the application of viscoelastic passive damping materials. Unconstrained layer damping treatments applied to metal plate systems were studied experimentally. Design and modelling of novel fibre reinforced constrained layer damping materials was performed, and implementation of these composite damping materials into laminated composite sandwich constructions commonly used as structural elements within large composite marine vessels was explored. These studies established effective methods for examining, designing and applying damping materials to metal and composite marine structures.
Two test fixtures were designed and constructed to facilitate testing of viscoelastic material damping properties to ISO 6721-3 and ASTM E756. Values of material damping made in accordance with ASTM E756 over a range of temperatures were compared to values produced by a Dynamic Mechanical Analyser (DMA). Glass transition temperatures and peak damping values were found to agree well, although results deviated significantly at temperatures above the glass transition temperature.
The relative influence of damping layer thickness, ambient temperature, edge conditions, plate dimensions and substrate material on the system damping performance of metal plates treated with an unconstrained viscoelastic layer was investigated experimentally. This investigation found that substrate material had the greatest influence on system damping performance, followed by damping layer thickness and plate size. Plate edge conditions were found to have little influence on the measured system damping performance. These results were dependent on the values of each variable used in the study.
Modal damping behaviour of a novel fibre reinforced composite constrained layer damping material was investigated using finite element analysis and experimental methods. The material consisted of two carbon fibre reinforced polymer (CFRP) layers surrounding a viscoelastic core. Opposing complex sinusoidal fibre patterns in the CFRP face sheets were used to achieve stress-coupling by way of orthotropic anisotopy about the core. A finite element model was developed in MATLAB to determine the modal damping, displacement, stress, and strain behaviour of these complex patterned fibre constrained layer damping (CPF-CLD) materials. This model was validated using experimental results produced by modal damping measurements on CPF-CLD beam test specimens. Studies of multiple fibre pattern arrangements found that fibre pattern properties and the resulting localised material property distributions influenced modal damping performance.
Inclusion of CPF-CLD materials in laminated composite sandwich geometries commonly used in marine hull and bulkhead constructions was studied experimentally. Composite sandwich beam test specimens were fabricated using materials and techniques frequently used in industry. It was found that the greatest increases in modal damping performance were achieved when the CPF-CLD materials were applied to bulkhead geometries, and were inserted within the sandwich structure, rather than being attached to the surface.
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Surano, Dominic E. "The Effectiveness of Damage Arrestment Devices in Delaying Fastener-Hole Interaction Failures in Carbon Fiber Polyurethane Foam Composite Sandwich Panels Subjected to Static and Dynamic Loading Under Increased Temperatures." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/436.
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A study was conducted to investigate simple, cost-effective manufacturing techniques to delay skin-core delamination, micro-buckling and bearing stress failures resulting from fastener-hole interactions. Composite sandwich panels, with and without damage arrestment devices (DADs), were subjected to monotonic compression at a rate of 5mm per second, and compression-compression fatigue at 50% yield at an amplitude of 65%, under temperatures of 75, 100, 125, 150, 175, and 200 °F.
The sandwiches tested were composed of two-layer cross-weave carbon fiber facesheets, a polyurethane foam core, and an epoxy film adhesive to join the two materials. The most successful method to delay the aforementioned failures involved milling rectangular slots in the foam core perpendicular to the holes and adding three additional layers of carbon fiber cross-weave. For the monotonic cases, the ultimate load increases were 97, 87, 100, 131, 96, and 119% for each of the respective temperatures listed above with a negligible weight increase. For the fatigue cases, the number of cycles for each test case was nearly identical. This still represents a large improvement because the yield used in the loading condition for the specimens with DADs was 97% greater than the specimens without DADs.
The experimental results were compared with a finite element model (FEM) built in Abaqus/CAE. The numeric and experimental results showed a strong correlation. All test specimens were manufactured and tested in the California Polytechnic State University Aerospace/Composites Laboratory.
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Portela, Alexandre Machado Aguiar. "Inspeção por ressonância magnética nuclear de painéis-sanduíche compósitos de grau aeronáutico." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-18012012-145718/.
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O presente trabalho objetivou desenvolver e implementar, em escala laboratorial, uma rotina experimental com base em Imageamento por Ressonância Magnética Nuclear (IRMN) de modo a verificar seu potencial como metodologia não-destrutiva aplicável à inspeção quali- e quantitativa de água e hidrocarbonetos líquidos aprisionados no interior de células de núcleos-colméia utilizados na confecção de painéis-sanduíche compósitos estruturais de grau aeronáutico. Tentativas foram também realizadas no sentido de se observarem e caracterizarem danos por amassamento de núcleos-colméia, assim como de se detectar a presença de resina polimérica na forma sólida, visando, desta feita, verificar o uso do IRMN na inspeção de componentes previamente reparados e/ou contendo excesso de resina por falha do processo de manufatura. Concluiu-se que IRMN é uma poderosa ferramenta para a detecção e a quantificação de líquidos puros e compostos, ricos em hidrogênio, contidos nas células de núcleos de amostras extraídas de painéis-sanduíche compósitos. O potencial do IRMN na identificação, e, portanto, na discriminação entre os diversos fluidos se mostrou bastante promissor, desde que se empreguem ferramentas de processamento e análise computadorizada de imagens a partir de programas computacionais de reconhecimento de padrões via redes neurais artificiais e/ou sistemas com base em conhecimento. A técnica de IRMN utilizada neste estudo não permitiu a captura de imagens de resina polimérica sólida, nem mesmo quando à esta foram adicionadas cargas de elementos intensificadores de sinais de RMN, tais como ferro e gadolíneo. Danos no núcleo-colméia tão pequenos quanto 1,0 mm de profundidade e 1,8 mm de diâmetro foram clara e inequivocamente imageados e delineados pela técnica IRMN, desde que estivessem permeados por fluido hidrogenado (ex. água). A quantificação de líquidos nos núcleos-colméia por intermédio de ferramentas computacionais simples (processadores e analisadores de imagens) foi muito bem sucedida no caso dos líquidos com relativamente alto ponto de fulgor, pois as massas fluidas se mantiveram constantes por períodos de tempo significativamente longos no interior das células analisadas.This work intended to develop and implement in laboratorial scale an experimental routine funded in Nuclear Magnetic Resonance Imaging (NMRI) in order to verify its potential as a non-destructive methodology for quali- and quantitative inspection of liquid water and hydrocarbons entrapped in honeycomb core cells utilized to build up aeronautical grade structural composite sandwich panels. Attempts were also carried out to observe and characterize crush damage of honeycomb core, as well as to detect solid polymer resin towards the use of NMRI to assess previously repaired components and/or containing in excess resin amount due to manufacturing process faults. It has been concluded that NMRI is a powerful tool in detecting and quantifying hydrogen-rich pure and compound liquids contained in core cells of composite sandwich samples. The NMRI potential in identifying and, therefore, discriminating several fluids has shown very promising as long as computed image processing and analysis tools are employed from pattern recognition software via artificial neural networks and/or knowledge-based systems. The utilized NMRI technique failed in imaging solid polymer resin, even when the latter was loaded with NMR-signal intensifier elements such as iron and gadolinium. Honeycomb core damages as small as 1.0 mm in depth and 1.8 mm in diameter were clearly and unambiguously imaged and delineated by the NMRI technique since they were permeated with hydrogenated fluid (ex., water). The quantification of liquids in honeycomb cores by means of simple computational tools (image processor and analyzer) was very successful in case of relatively high flash point fluids, insofar as their masses remained constant within the analyzed cells for significantly long periods of time.
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Weidermann, Frank, Stefanie Zimmermann, and Andrea Pino. "Konstruktion eines Inserts für Faserverbund- Halbzeuge." Thelem Universitätsverlag & Buchhandlung GmbH & Co. KG, 2021. https://tud.qucosa.de/id/qucosa%3A75902.
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Sandwichplatten sind effiziente Leichtbauelemente. Sie werden im Fahrzeugbau, in der Luft- und Raumfahrt, im Werkzeugmaschinenbau und überall dort, wo es auf geringe bewegte Massen ankommt, eingesetzt. Sandwichplatten sind oft Halbzeuge. Sandwichbauteile haben oft einen aufwendigen Herstellungsprozess, der eine Wärmebehandlung, die höhere Genauigkeiten ausschließt, beinhaltet. Aus diesen Gründen ist es oft sinnvoll, Inserts erst im Nachhinein in die fertige Sandwichplatte bzw. in das fertige Sandwichbauteil einzusetzen. Diese Inserts haben unterschiedliche Aufgaben. Sie dienen z.B. der Aufnahme von Schrauben, Bolzen und Lagern. Die vorgestellte Verbindung entspricht durch ihre spezielle Geometrie den hohen Anforderungen für Verbindungselemente in den genannten Gebieten hinsichtlich Genauigkeit und Stabilität. Es wird der Konstruktionsprozess eines Inserts für Sandwichplatten aus CFK- Verbundmaterial beschrieben. Ausgehend von einer patentierten Lösung der Autoren findet eine schrittweise Produktverbesserung bis hin zu einem einsatzfähigen Prototypen statt. Durch die Insertverbindung können für den Maschinenbau erforderliche Genauigkeiten nun mit CFK- Halbzeugen umgesetzt werden. Die Anwendung dieses Leichtbaupotentials führt zur Energieeinsparung und zum Transfer von CFK- Anwendungen in den Maschinenbau.
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Hu, Bo. "Bio-based composite sandwich panel for residential construction." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 5.24 Mb., 265 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3221055.
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Phan, Catherine Ninh. "The extended high-order sandwich panel theory." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43578.
Full textAbstract:
A new high order theory, referred to as the Extended High-Order Sandwich Panel Theory (EHSAPT), was formulated for orthotropic sandwich beams/wide panels with a general layout. This new theory accounts for the axial, transverse normal, and shear rigidity of the core. Validation of the present theory was performed for several structural analysis problems including: static loading, static instability (global buckling and wrinkling), free vibrations (natural frequencies), and dynamic loading (blast and impact). The accuracy of the theory was assessed by comparison with elasticity solutions and with experiment. It is shown that this new theory has superior accuracy over other available computational models, especially for sandwich beams/wide panel configurations with stiffer cores.
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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.