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Yu, Chaoming. "Three-dimensional analysis of composite structural elements at elevated temperatures." Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443508.
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Duchateau, Kristin Anne. "Structural design and performance of composite wall-foundation connector elements." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Thesis/Summer2005/k%5Fduchateau%5F071405.pdf.
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Flor, Felipe Rendeiro. "Damage monitoring in composite structures via vibration based method: metal-composite bonded joints and sandwich structures." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18148/tde-04042016-161659/.
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The present document covers the studies over Structural Health Monitoring systems via vibration based methods. The topic is organized in two parallel studies. The first one analyzes the integrity of metal-composite single lap bonded joints. The second one approaches similar analyses for sandwich structures. The monitoring was made by investigating the dynamic response both computationally and experimentally to verify the reliability of applying vibration based SHM procedures, specifically with the objective of identifying the presence of debonding damage. The dynamic responses were obtained via accelerometers and piezoelectric sensors placed on top of the investigated structures (on the outward surface). The purpose for the accelerometers is to provide reference data for the analyses involving the piezoelectric sensors. Different metrics of damage identification were investigated, all working over a determined frequency range. They quantify the damage by analyzing either the magnitudes or phase angles of the dynamic responses among the undamaged and damage structures. This present work proposed modifications to some methodologies of damage quantification found in the literature and compared the results. The new metrics offered more reliable values for the damage quantification on several of the analyses. It was verified that the metrics are valid for the scenarios observed in the present study. The experimental analyses showed also the influence on the dynamic response due to the position of small elastomeric elements. In regards to the finite element analyses, the computational models showed similar results to the experimental data, the more accurate ones being the models for the bonded joints. For the computational models, improvements can be applied into the piezoelectric sensor (e.g. by using new finite element formulations), as well as the region of debonding (e.g. by using contact algorithms). It is important to highlight that the elastic properties of the skins for the sandwich structure were obtained by the literature, so the model can be improved in the future by applying properties obtained experimentally.Esta dissertação aborda os estudos realizados no campo de Sistemas de Monitoramento da Integridade Estrutural por meio de métodos baseados em vibrações. O tópico abordado é organizado em dois estudos paralelos. O primeiro é relativo ao monitoramento da integridade de juntas coladas metal-compósito. O segundo versa sobre análises semelhantes em estruturas sanduíche. O monitoramento foi executado através das análises das assinaturas dinâmicas das estruturas, tanto computacionalmente quanto experimentalmente, visando avaliar a capacidade de metodologias vibracionais de SHM em detectar dano de descolamento. As respostas dinâmicas foram obtidas por meio de acelerômetros e sensores piezelétricos dispostos sobre a superfície das estruturas avaliadas. Os acelerômetros fornecem dados de referência para as análises realizadas com base nas respostas do sensor piezelétrico. Diferentes métricas de identificação de dano são abordadas, sendo que todas estão baseadas em análise no domínio da frequência, utilizando parâmetros de magnitude ou ângulo de fase das estruturas danificadas e intactas. O presente trabalho propôs alterações em algumas das metodologias encontradas na literatura e comparou os resultados das métricas originais com as modificadas. As métricas modificadas apresentaram resultados mais consistentes em vários cenários de análise. Constatou-se também que as métricas abordadas mostram-se válidas para os casos observados no presente estudo. As análises experimentais também evidenciaram a influência na assinatura dinâmica da estrutura sanduíche causada pelo posicionamento de pequenos elementos elastoméricos. Com relação às análises via elementos finitos, os modelos computacionais apresentaram resultados similares aos obtidos experimentalmente, sendo os da junta colada os mais precisos. Tais modelos computacionais podem ser melhorados no futuro por meio de uma modelagem mais detalhada dos elementos piezelétricos (por exemplo: por meio de novas formulações), como também da região de descolamento (por exemplo: por meio da implementação de algoritmos de contato). Deve-se ressaltar também que as propriedades elásticas das lâminas externas da estrutura sanduíche foram obtidas da literatura, assim sendo, o modelo poderá ser melhorado em estudos futuros por meio do emprego de propriedades obtidas experimentalmente.
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Klinsky, Gelafito Eduardo René Gutiérrez. "Uma contribuição ao estudo das pontes em vigas mistas." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-08122017-110333/.
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Este estudo fundamenta-se na análise numérica, via elementos finitos, de pontes em vigas mistas; considera-se a interação de todos os elementos que compõem a estrutura na transferência dos esforços até os apoios. Inicialmente apresenta-se um estado da arte sobre o projeto, execução e análise de pontes em vigas mistas, identificando as simplificações e deficiências existentes no cálculo destas estruturas. O estudo do comportamento estrutural de tabuleiros mistos foi abordado do ponto de vista tridimensional, sendo para isto modelados e analisados tabuleiros com 8, 10, 12, 14, 16, 18, 20, 22, 24 e 26 m. de vão mediante a utilização do programa ANSYS, versão 5.4. Foi estudada a influência que a presença de contraventamentos, espessura da laje, vão e posição da carga móvel na seção transversal exercem na distribuição de cargas nas vigas, sendo para isto considerado comportamento elástico-linear. Realizou-se também uma abordagem ao estudo da redundância estrutural de tabuleiros mistos considerando as não linearidades física e geométricas do conjunto. Foi verificado que tabuleiros sobre duas e quatro vigas mantêm o equilíbrio estático após que uma das vigas sofre fratura, sem experimentar grandes deslocamentos (inferiores ou ligeiramente superiores ao limite L/500).This work is based in the numerical analysis, by finite elements, of bridge decks with composite beams; in this study the interaction of all the elements that compose the structure is considered in the transference of the efforts to the supports. lnitially, a state of the art on the design, construction and analysis of composite bridge decks is presented, identifying the simplifications adopted, lack of information at the present on the subject and aspects that need further studies on this bridges. The study of the structural behavior of composite bridge decks was approached from a three-dimensional point of view, modeling and analyzing composite decks with 8, 10, 12, 14, 16, 18, 20, 22, 24 and 26 m of span by using the software ANSYS, version 5.4. The influence that the bracing system, thickness of the slab, span and live load position on the deck, over the load distribution in the composite beams, considering linear-elastic behavior, was studied. An approach to the study of the structural redundancy of composite bridge decks was also made, considering the physical and geometric nonlinearities of the structure. lt was verified that decks consisting of two and four composite beams maintain the static equilibrium after the fracture of one of the beams, without large displacements (inferior or lightly superior to the limit L/500).
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Cardozo, López Sergio Daniel. "Otimização de placas e cascas de materiais compósitos, utilizando algoritmos genéticos, redes neurais e elementos finitos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2009. http://hdl.handle.net/10183/18583.
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A otimização estrutural, utilizando ferramentas computacionais é um grande campo de pesquisa na atualidade. Os métodos utilizados, dependendo da complexidade do problema, demandam um grande custo computacional, e por isso vem sendo avaliandas várias técnicas para diminuí-lo. Uma delas é o emprego de técnicas de aproximação de análises, dentre as quais destacam-se as redes neurais, que combinadas aos métodos de otimização e de análises clássicos conseguem bons resultados e reduzem significativamente o tempo de processamento. O emprego dos compósitos laminados como material estrutural vem crescendo nos últimos tempos, incentivado pela suas excelentes propriedades mecânicas e baixo peso. Em consenso com todo o esforço científico dedicado a essa área, o presente trabalho visa a implementação de uma ferramenta computacional capaz de otimizar estruturas complexas fabricadas com tais materiais, a um baixo custo computacional. Com isto em mente, é desenvolvido um sistema de otimização, aproveitando módulos implementados previamente para a análise estática linear e não linear através do método dos elementos finitos (MEF), e o módulo de otimização por algoritmos genéticos. Serão desenvolvidos os módulos de análise modal, para otimizar também estruturas com critérios baseados em freqüências e modos, e o modulo de redes neurais de tipo perceptron para aproximações das análises feitas através do MEF. Alguns exemplos são apresentados para demonstrar que bons resultados são obtidos com a utilização de redes neurais artificiais, cujo treinamento permite poupar tempo computacional proveniente do grande número de análises usualmente necessárias no processo de otimização.Structural optimization using computational tools has become a major research field in recent years. Methods commonly used in structural analysis and optimization may demand considerable computational cost, depending on the problem complexity. Therefore, many techniques have been evaluated in order to diminish such impact. Among these various techniques, artificial neural networks may be considered as one of the main alternatives, when combined with classic analysis and optimization methods, to reduce the computational effort without affecting the final solution quality. Use of laminated composite structures has been continuously growing in the last decades due to the excellent mechanical properties and low weight characterizing these materials. Taken into account the increasing scientific effort in the different topics of this area, the aim of the present work is the formulation and implementation of a computational code to optimize manufactured complex laminated structures with a relatively low computational cost by combining the Finite Element Method (FEM) for structural analysis, Genetic Algorithms (GA) for structural optimization and Artificial Neural Networks (ANN) to approximate the finite element solutions. The modules for linear and geometrically non-linear static finite element analysis and for optimize laminated composite plates and shells, using GA, were previously implemented. Here, the finite element module is extended to analyze dynamic responses to optimize problems based in frequencies and modal criteria, and a module with perceptron ANN is added to approximate finite element analyses. Several examples are presented to show the effectiveness of ANN to approximate solutions obtained using the FEM and to reduce significatively the computational cost.
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Schneider, Hartwig N., Christian Schätzke, Christiane Feger, Michael Horstmann, and Daniel Pak. "Modulare Bausysteme aus Textilbeton-Sandwichelementen." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1244051494649-79626.
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Sandwichelemente mit Deckschichten aus Textilbeton und tragenden Dämmkernen verfügen über ein breites Leistungsprofil, von selbsttragenden Fassadenbauteilen bis zu tragenden Wand-, Dach- und Deckenbauteilen. Trotz der geringen Bauteilstärke von nur 18 – 20 cm besitzen Sandwichelemente aus Textilbeton neben der hohen Tragfähigkeit ein günstiges bauphysikalisches Verhalten hinsichtlich des Wärme- und Schallschutzes. Anhand eines kleinen Experimentalbaus wurde im Rahmen des Sonderforschungsbereichs SFB 532 an der RWTH Aachen die Anwendbarkeit von tragenden Sandwichbauteilen verifiziert. Dabei wurden wesentliche Fragestellungen wie Konstruktion und Gestalt, Tragverhalten, Bauteilfügung, Herstellungstechnik und Montage untersucht.
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Isildak, Murat. "Use Of Helical Wire Core Truss Members In Space Structures." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610553/index.pdf.
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In an effort to achieve lighter and more economical space structures, a new patented steel composite member has been suggested and used in the construction of some steel roof structures. This special element has a sandwich construction composed of some strips of steel plates placed longitudinally along a helical wire core. The function of the helical core is to transfer the shear between the flange plates and increase the sectional inertia of the resulting composite member by keeping the flange plates at a desired distance from each other. Because of the lack of research, design engineers usually treat such elements as a solid member as if it has a full shear transfer between the flanges. However, a detailed analysis shows that this is not a valid assumption and leads to very unsafe results. In this context, the purpose of this study is to investigate the behavior of such members under axial compression and determine their effective sectional flexural rigidity by taking into account the shear deformations. This study applies an analytical investigation to a specific form of such elements with four flange plates placed symmetrically around a helical wire core. Five independent parameters of such a member are selected for this purpose. These are the spiral core and core wire diameters, the pitch of the spiral core, and the flange plate dimensions. Elements with varying combinations of the selected parameters are first analyzed in detail by finite element method, and some design charts are generated for the determination of the effective sectional properties to be used in the structural analysis and the buckling loads. For this purpose, an alternative closed-form approximate analytical solution is also suggested.
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Somanath, Nagendra. "A finite element cure model and cure cycle optimization for composite structures." Thesis, This resource online, 1987. http://scholar.lib.vt.edu/theses/available/etd-04272010-020304/.
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Pulido, Antonio Carlos. "Influência do comportamento das ligações na estabilidade de estruturas mistas de aço e concreto." Universidade Federal de São Carlos, 2014. https://repositorio.ufscar.br/handle/ufscar/4701.
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Previous issue date: 2014-06-16The objective of this work was to evaluate the influence of the rigidity of the beam-tocolumn connections as well as the transference of forces among the structural components in steel-concrete composite structures. to do this, data regarding the Moment vs. Rotation curve behavior of a concrete filled beam-to-column connection, previously evaluated on a different work was used for comparison. The experimental value of rigidity was inserted into models of plane frames and tridimensional models, in a way that the global stability parameters can be evaluated according to the rotational stiffness of the beam-to-column connections. In order to evaluate the stability, was led in consideration the ABNT NBR 8800:2008 Brazilian code recommendations. For the numeric simulations, the software SAP 2000® was used, in which it was simulated a plane frame model with ten floors, and also a tridimensional frame, varying the number of floors. Once constructed the numerical models, for the plane frame comparative analysis were performed study of the redistribution of forces, of consumption of steel and stability considering that the beam-to-column connections represented in the models, simulate the following situations regarding the system stiffness: rigid and semi-rigid connections and also ratios of experimental stiffness. For the tridimensional model, besides the variation of the stiffness connection the influence of number of floors on the parameters of stability and distribution of forces on structural elements was also analyzed in the present study. The results showed that the stiffness of the beam-to-connections alters the distribution of forces, and that the variation on the number of floors have influence on the global stability parameter. However, it is possible to design structures with semi-rigid beam-to-column connections respecting the normative limits for the parameters of stability and reducing the consumption of steel in the form of profiles.
O objetivo deste trabalho é avaliar a influência da rigidez das ligações viga-pilar no comportamento e na transferência de forças entre componentes estruturais de sistemas estruturados em elementos mistos de aço e concreto. Para isso, serão utilizados dados do comportamento Momento vs. Rotação de uma ligação viga-pilar misto preenchido já investigada experimentalmente. Os resultados experimentais de rigidez serão inseridos em modelos de pórticos planos e tridimensionais, de forma que os parâmetros de estabilidade global possam ser avaliados em função da rigidez da ligação viga-pilar. Para o estudo da estabilidade são consideradas as recomendações da norma brasileira de estruturas de aço e mistas ABNT NBR 8800:2008. Para as simulações numéricas foi utilizado o pacote computacional SAP 2000® no qual foi modelado um pórtico plano com dez pavimentos e um pórtico tridimensional, variando-se o número de pavimentos e a rigidez das ligações. Para o pórtico plano foram realizadas análises comparativas da distribuição de esforços, do consumo de aço e da estabilidade considerando que as ligações viga-pilar representadas no modelo simulem as seguintes situações quanto à rigidez: ligações rígida e semirrígida, cuja rigidez foi determinada experimentalmente, além de parcelas desta rigidez experimental. Para os pórticos tridimensionais, além da variação de rigidez, foi analisada a influência do número de pavimentos sobre os parâmetros de estabilidade e distribuição de esforços nos elementos estruturais. Os resultados mostraram que a rigidez das ligações altera a distribuição dos esforços e a variação no número de pavimentos influencia nos parâmetros de estabilidade global. No entanto, é possível conceber estruturas com ligações viga-pilar semirrígidas respeitando os limites normativos para os parâmetros de estabilidade e reduzindo o consumo de aço sob a forma de perfis.
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Muliana, Anastasia Hanifah. "Integrated Micromechanical-Structural Framework for the Nonlinear Viscoelastic Behavior of Laminated and Pultruded Composite Materials and Structures." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5142.
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This study introduces a new three-dimensional (3D) multi-scale constitutive framework for the nonlinear viscoelastic analysis of laminated and pultruded composites. Two previously developed nonlinear micromechanical models for unidirectional and in-plane random composite layers are modified to include time-dependent and nonlinear behavior. A new recursive-iterative numerical integration method is introduced for the Schapery nonlinear viscoelastic model and is used to model the isotropic matrix subcells in the two micromodels. In addition, a sublaminate model is used to provide for a through-thickness 3D nonlinear equivalent continuum of a layered medium. The fiber medium is considered as transversely isotropic and linear elastic. Incremental micromechanical formulations of the above three micromodels are geared towards the time integration scheme in the matrix phase. New iterative numerical algorithms with predictor-corrector type steps are derived and implemented for each micromodel to satisfy both the constitutive and homogenization equations. Experimental creep tests are performed for off-axis pultruded specimens in order to calibrate and examine the predictions of the constitutive framework for the multi-axial nonlinear viscoelastic response. Experimental creep data, available in the literature, is also used to validate the micromodel formulation for laminated composite materials. Nonlinear viscoelastic effects at the matrix level, such as aging, temperature, and moisture effects can be easily incorporated in the constitutive framework. The multi-scale constitutive framework is implemented in a displacement-based finite element (FE) code for the analysis of laminated and pultruded structures. Several examples are presented to demonstrate the coupled multi-scale material and structural analysis.
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Padhi, Gouri S. "Numerical failure modeling of composite structures." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312862.
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Taylor, Joshua Michael. "Nonlinear analysis of steel frames with partially restrained composite connections and full or partially composite girders." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19272.
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Tenek, Lazarus. "Finite-element natural-mode analysis of arbitrary composite shells." Thesis, University of Westminster, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339247.
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Horton, Brandon Alexander. "Comprehensive Multi-Scale Progressive Failure Analysis for Damage Arresting Advanced Aerospace Hybrid Structures." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/93961.
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In recent years, the prevalence and application of composite materials has exploded. Due to the demands of commercial transportation, the aviation industry has taken a leading role in the integration of composite structures. Among the leading concepts to develop lighter, more fuel-efficient commercial transport is the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept. The highly integrated structure of PRSEUS allows pressurized, non-circular fuselage designs to be implemented, enabling the feasibility of Hybrid Wing Body (HWB) aircraft. In addition to its unique fabrication process, the through-thickness stitching utilized by PRSEUS overcomes the low post-damage strength present in typical composites. Although many proof-of-concept tests have been performed that demonstrate the potential for PRSEUS, efficient computational tools must be developed before the concept can be commercially certified and implemented.
In an attempt to address this need, a comprehensive modeling approach is developed that investigates PRSEUS at multiple scales. The majority of available experiments for comparison have been conducted at the coupon level. Therefore, a computational methodology is progressively developed based on physically realistic concepts without the use of tuning parameters. A thorough verification study is performed to identify the most effective approach to model PRSEUS, including the effect of element type, boundary conditions, bonding properties, and model fidelity. Using the results of this baseline study, a high fidelity stringer model is created at the component scale and validated against the existing experiments. Finally, the validated model is extended to larger scales to compare PRSEUS to the current state-of-the-art.
Throughout the current work, the developed methodology is demonstrated to make accurate predictions that are well beyond the capability of existing predictive models. While using commercially available predictive tools, the methodology developed herein can accurately predict local behavior up to and beyond failure for stitched structures such as PRSEUS for the first time. Additionally, by extending the methodology to a large scale fuselage section drop scenario, the dynamic behavior of PRSEUS was investigated for the first time. With the predictive capabilities and unique insight provided, the work herein may serve to benefit future iteration of PRSEUS as well as certification by analysis efforts for future airframe development.PHD
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Ananthasubramanian, Srikanth, and Priyank Gupta. "Early assessment of composite structures : Framework to analyse the potential of fibre reinforced composites in a structure subjected to multiple load case." Thesis, KTH, Lättkonstruktioner, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-235309.
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To meet the need of lightweight chassis in the near future, a technological step of introducing anisotropic materials like Carbon Fibre Reinforced Plastics (CFRP) in structural parts of cars is a possible way ahead. Though there are commercially available tools to find suitability of Fibre Reinforced Plastics (FRPs) and their orientations, they depend on numerical optimization and complexity increases with the size of the model. Nevertheless, the user has a very limited control of intermediate steps. To understand the type of material system that can be used in different regions for a lightweight chassis, especially during the initial concept phase, a more simplified, yet reliable tool is desirable.The thesis aims to provide a framework for determining fibre orientations according to the most-ideal loading path to achieve maximum advantage from FRP-materials. This has been achieved by developing algorithms to find best-fit material orientations analytically, which uses principal stresses and their orientations in a finite element originating from multiple load cases. This thesis takes inspiration from the Durst criteria (2008) which upon implementation provides information on how individual elements must be modelled in a component subjected to multiple load cases. This analysis pre-evaluates the potential of FRP-suitable parts. Few modifications have been made to the existing formulations by the authors which have been explained in relevant sections.The study has been extended to develop additional MATLAB subroutines which finds the type of laminate design (uni-directional, bi-axial or quasi-isotropic) that is suitable for individual elements.Several test cases have been run to check the validity of the developed algorithm. Finally, the algorithm has been implemented on a Body-In-White subjected to two load cases. The thesis gives an idea of how to divide the structure into sub-components along with the local fibre directions based on the fibre orientations and an appropriate laminate design based on classical laminate theory.
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Le, Thi Huyen Cham. "Robust variable kinematics plate finite elements for composite structures." Thesis, Paris 10, 2019. http://faraway.parisnanterre.fr/login?url=http://bdr.parisnanterre.fr/theses/intranet/2019/2019PA100053/2019PA100053.pdf.
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Le but de ce travail est de développer deux nouveaux éléments finis quadrilatéraux à quatre et à huit nœuds implantés dans le code commercial de calcul par Eléments Finis (EF) Abaqus pour plaques composites. Les modèles plaques à cinématique variable sont formulés dans le cadre de la formulation unifiée de Carrera (CUF), qui regroupent des descriptions de type: couche équivalente (ESL) et couches discrètes (LW), avec les variables définies par des polynômes jusqu’au 4ème ordre suivant épaisseur z. Les deux formulations variationnelles sont utilisées pour dériver les matrices des éléments finis: le Principe des Déplacements Virtuels (PVD) et le Théorème Variationnel Mixte de Reissner (RMVT). Grâce à la technique de condensation statique, une formulation hybride basée sur le RMVT est introduite. Afin d’éliminer la pathologie de verrouillage en cisaillement transverse, deux approximations compatibles pour le champ de déformations de cisaillement transverse indépendantes en z, notée QC4 et CL8, sont étendues aux éléments plaques à cinématique variable basés sur CUF. De plus, les QC4S et CL8S interpolations sont également introduites pour les contraintes de cisaillement transverse dans les éléments mixtes et les éléments hybrides. Les résultats numériques comparés à ceux disponibles dans la littérature montrent que les FE proposés sont efficaces pour modéliser des éléments finis robustesThe aim of this work is the development of two classes of new four-node and eightnode quadrilateral finite elements implemented into the commercial finite element (FE) code Abaqus for composite plates. Variable kinematics plate models are formulated in the framework of Carrera’s Unified Formulation (CUF), which encompasses Equivalent Single Layer (ESL) as well as Layer-Wise (LW) models, with the variables that are defined by polynomials up to 4th order along the thickness direction z. The two classes refer to two variational formulations that are employed to derive the finite elements matrices, namely the Principle of Virtual Displacement (PVD) and Reissner’s Mixed Variational Theorem (RMVT). Thanks to the static condensation technique, a Hybrid formulation based on the RMVT is derived. For the purpose of eliminating the shear locking pathology, two field compatible approximations for only the z−constant transverse shear strain terms, referred to as QC4 and CL8 interpolations, are extended to all variable kinematics CUF plate elements. Moreover, the QC4S and CL8S interpolations, are also introduced for the transverse shear stress field within RMVT-based and Hybrid mixed-based elements. Numerical results in comparison with those available in literature show that the proposed FEs are efficient for modeling a robust finite elements
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Liu, Xiao Bin. "Finite element analysis of hybrid thermoplastic composite structures." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493330.
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A wide range of thermoplastic composites (TPC) are now being used in automotive applications including vehicle front-end structures, load floors, seat backs, door cassettes and instrument panels. Long fibre thermoplastics (LFT), glass mat thermoplastics (GMT) and fully structural materials such as woven commingled fabric TPCs, e.g. Twintex®, provide a range of properties and mouldability appropriate to specific applications.
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Qureshi, Jawed Qureshi. "Finite element modelling of steel-concrete composite structures." Thesis, University of Leeds, 2010. http://etheses.whiterose.ac.uk/21112/.
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The main objective of this research is to contribute to the knowledge and understanding of the behaviour of the headed stud shear connector in composite beams with trapezoidal profiled metal decking laid perpendicular to the axis of the beam through experimental and numerical studies. Push tests are used to study the behaviour of composite beams. A three-dimensional finite element model of the push test is developed using the general purpose finite element program ABAQUS and the push test is analysed using different concrete material models, and analysis procedures. The Concrete Damaged Plasticity model with dynamic explicit analysis procedure is found to have matched with experimental results very well in terms of the shear connector resistance, load-slip behaviour and failure mechanisms. The post-failure behaviour of the push test, which has not been modelled in the past, is accurately predicted in this study with the help of this modelling technique. The experimental investigation is conducted with a single-sided horizontal push test arrangement to study the influence of various parameters such as normal load, number of shear studs, reinforcement bar at the bottom trough, number of layers of mesh, position of mesh, position of normalload and various push test arrangements. To assess the accuracy and reliability of the developed finite element model, it is validated against push test experiments conducted in this study and variety of push tests carried out by other authors with different steel decks and shear stud dimensions, positions of the shear stud within a rib and push test arrangements. The results obtained from the finite element analysis showed excellent agreement with the experimental studies. The validated finite element model is used in a parametric study to investigate the effect of shear stud position, thickness of the profiled sheeting, shear connector spacing and staggering of shear studs on the performance of the shear stud. The results of the parametric study are evaluated and findings are used to propose the design equations for shear connector resistance taking into account the position of the shear stud and thickness of the profiled sheeting. The coefficient of correlation between experimental and predicted results is nearly equal to one, which indicates that the predicted results are accurate, and the proposed equations are suitable for future predictions.
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Fayad, Ghassan Najib. "Probabilistic Finite Element Analysis of Marine Grade Composites." Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/FayadGN2005.pdf.
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Sokmen, Ozlem. "Structural Optimization Of A Composite Wing." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607715/index.pdf.
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In this study, the structural optimization of a cruise missile wing is accomplished for the aerodynamic loads for four different flight conditions. The flight conditions correspond to the corner points of the V-n diagram. The structural analysis and optimization is performed using the ANSYS finite element program. In order to construct the flight envelope and to find the pressure distribution in each flight condition, FASTRAN Computational Fluid Dynamics program is used.
The structural optimization is performed for two different wing configurations. In the first wing configuration all the structural members are made up of aluminum material. In the second wing configuration, the skin panels are all composite material and the other members are made up of aluminum material. The minimum weight design which satisfies the strength and buckling constraints are found for both wings after the optimization analyses.
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Brown, Adrian D. "The use of carbon fibre reinforced cement as tensile reinforcement for concrete structural elements." Thesis, University of Bath, 1987. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287533.
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Odi, A. R. A. "Bonded Repair of Composite Structures; A Finite Element Approach." Thesis, Department of Materials and Medical Sciences, 2009. http://hdl.handle.net/1826/3893.
Full textAbstract:
This thesis addresses the issues surrounding the application of the finite element
method to analyse composite structure repairs with an emphasis on aircraft
applications. A comprehensive literature survey has been carried out for this purpose
and the results are presented.
A preliminary study and a comparative study of different modelling approaches have
been completed. These studies aim to explore and identify the problems in modelling
repairso n simplec ompositep anelsw ith speciala ttention given to adhesivem odelling.
Three modelling approaches have been considered: Siener's model which is an
extension of the traditional plane strain 2D model used for adhesively bonded joints,
Bait's model which is a promising new approach and a full 3D model. These studies
have shown that these methods are complementary providing a different insight into
bonded repairs. They have also highlighted the need for a new modelling approach
which will provide an overall view of bonded repairs.
Improved modelling approachesh ave been developedf or externallyb onded patch and
flush repairs. These models enable the study of adhesive failure as well as composite
adherendf ailures.T hesea pproachesh aveb eena ppliedt o real repairs and the predicted
results compared to experimental data. Four case studies have been conducted:
external bonded patch repairs to composite plates, a scarf joint for bonded repairs, a
flat panel repaired with a scarfed patch and a repaired curved panel.
These case studies have shown that bonded repairs to composite structures can be
analyseds uccessfullyu sing PC-basedc ommercialf inite elementc odes.
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Odi, A. Randolph A. "Bonded repair of composite structures : a finite element approach." Thesis, Cranfield University, 1998. http://dspace.lib.cranfield.ac.uk/handle/1826/3893.
Full textAbstract:
This thesis addresses the issues surrounding the application of the finite element method to analyse composite structure repairs with an emphasis on aircraft applications. A comprehensive literature survey has been carried out for this purpose and the results are presented. A preliminary study and a comparative study of different modelling approaches have been completed. These studies aim to explore and identify the problems in modelling repairso n simplec ompositep anelsw ith speciala ttention given to adhesivem odelling. Three modelling approaches have been considered: Siener's model which is an extension of the traditional plane strain 2D model used for adhesively bonded joints, Bait's model which is a promising new approach and a full 3D model. These studies have shown that these methods are complementary providing a different insight into bonded repairs. They have also highlighted the need for a new modelling approach which will provide an overall view of bonded repairs. Improved modelling approachesh ave been developedf or externallyb onded patch and flush repairs. These models enable the study of adhesive failure as well as composite adherendf ailures.T hesea pproachesh aveb eena ppliedt o real repairs and the predicted results compared to experimental data. Four case studies have been conducted: external bonded patch repairs to composite plates, a scarf joint for bonded repairs, a flat panel repaired with a scarfed patch and a repaired curved panel. These case studies have shown that bonded repairs to composite structures can be analyseds uccessfullyu sing PC-basedc ommercialf inite elementc odes.
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Alej, Fateh. "Methodology of micromechanical finite element analysis of structural textile composites." Thesis, University of Manchester, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488415.
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Neogi, Sudipto. "Design of large composite structures using global optimization and finite element analysis /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/7082.
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Hegaze, Moutaz Mohamed Ebrahim. "Finite element analysis of fatigue damage of composite laminated structures." Thesis, Cranfield University, 2002. http://hdl.handle.net/1826/4064.
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Composite materials are increasingly believed to be the materials of the future with potential for
application in high perfon-nance structures. One of the reasons for that is the indication that
composite materials have a rather good rating with regard to life time in fatigue. Fatigue of
composite materials is a quite complex phenomenon, and the fatigue behaviour of these
heterogeneous materials is fundamentally different from the behaviour of metals. Finite element
method is a powerful numerical technique for the solution of such complex problems. The
present work comprises theoretical and experimental research into the implementation of
composite materials in structure applications. A new finite element derivation was carried out
based on a high-order shear deformation theory, which is accurate for a wide range of thickness.
The geometric nonlinearity effect was considered in the derivation of the element. The force
increment method was also introduced to improve the accuracy of nonlinear analysis.
Experimental measurements were carried out with two different types of composite materials,
carbon/epoxy and glass/epoxy, in order to obtain fatigue life diagrams (S/N diagrams) to be used
for the fatigue damage assessment.F atigue damage assessmentsw ere developed to predict the
fatigue behaviour of laminated plates and shells based on two aspects; damage by initiation and
damage by crack growth. A computer package was built based on the proposed finite element
theory to carry out the previous analyses. Several finite element solvers and eigenproblem solvers
are available to users of the package to choose the suitable one for their applications. The
validation of the developed package for some analyses such as stress analysis, natural frequency
analysis, stability analysis and fatigue analysis was successfully achieved using a number of
composite case studies. A parametric study was also carried out to illustrate the potential of the
package to be used as a good optimization tool. Fatigue life assessment by damage growth has
been achieved by a single run of the package, thus saving enormous user effort and computer
resources, compared with the use of commercial finite element packages.
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Cooper, Edward. "An elastic-plastic finite element model for composite crash structures." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268468.
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Kapoor, Hitesh. "Isogeometric Finite Element Code Development for Analysis of Composite Structures." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/50567.
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This research endeavor develops Isogeometric approach for analysis of composite structures and take advantage of higher order continuity, smoothness and variation diminishing property of Nurbs basis for stress analysis of composite and sandwich beams and plates. This research also computes stress concentration factor in a composite plate with a hole.Isogeometric nonlinear/linear finite element code is developed for static and dynamic analysis of laminated composite plates. Nurbs linear, quadratic, higher-order and k-refined elements are constructed using various refinement procedures and validated with numerical testing. Nurbs post-processor for in-plane and interlaminar stress calculation in laminated composite and sandwich plates is developed. Nurbs post-processor is found to be superior than regular finite element and in good agreement with the literature. Nurbs Isgoemetric analysis is used for stress analysis of laminated composite plate with open-hole. Stress concentration factor is computed along the hole edge and good agreement is obtained with the literature. Nurbs Isogeometric finite element code for free-vibration and linear dynamics analysis of laminated composite plates also obtain good agreement with the literature.
Main highlights of the research are newly developed 9 control point linear Nurbs element, k-refined and higher-order Nurbs elements in isogeometric framework. Nurbs elements remove shear-locking and hourglass problems in thin plates in context of first-order shear deformation theory without the additional step and compute better stresses than Lagrange finite element and higher order shear deformation theory for comparatively thick plates i.e. a/h = 4. Also, Nurbs Isogeometric analysis perform well for vibration and dynamic problems and for straight and curved edge problems.
Ph. D.
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Younes, Mahmoud. "Modelisation d'un element de structure composite a noyau leger gaine." Paris, ENSAM, 1986. http://www.theses.fr/1986ENAM0003.
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Dans le cadre de la conception d'engins de recherche et d'exploitation en mer, profonde, nous nous interessons aux poutres composites a noyau leger gaine. Le noyau est constitue d'une mousse syntactique. La gaine est une enveloppe composite stratifiee. Cette etude comprend principalement deux grandes parties; une modelisation theorique et une analyse experimentale. La partie theorique est basee sur les hypotheses de navier-bernouilli pour les problemes de flexion et celles de vlassov pour les problemes de torsion et prend en compte les deformations de cisaillement introduites en valeurs moyennes entre deux sections droites voisines. Ce modele assure egalement la continuite des deplacements entre le noyau et la gaine. Nous modelisons un element "p. C. N. L. G" et nous introduisons les conditions aux limites, notamment des forces de liaison aux noeuds de cet element pour etablir la relation matricielle de comportement par l'application du principe des puissances virtuelles. L'analyse experimentale a pour objet de caracteriser les materiaux constituant la structure et de qualifier sur des modeles dits de "validation" le modele theorique dont on vient de definir les grandes lignes. L'element "p. C. N. L. G" permet d'analyser les structures en lignes ou des structures spatiales, necessitant neanmoins et ulterieurement la realisation d'un element de junction assurant l'assemblage des elements poutres. Les applications de cette etude peuvent etre developpees dans la conception des flotteurs, des tubes, des engins, etc. . .
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Geyer, Susanna Elizabeth. "Advanced low order orthotropic finite element formulations." Diss., Pretoria : [s.n.], 2001. http://upetd.up.ac.za/thesis/available/etd-03062006-114313/.
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Serra, Joël. "Etude expérimentale et numérique de la propagation de coupure dans des stratifiés composites soumis à des chargements complexes." Thesis, Toulouse, ISAE, 2016. http://www.theses.fr/2016ESAE0027/document.
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La sensibilité des structures composites à la présence d'endommagements importants en zones singulières (trou, pointe d'entaille.. impose d'évaluer leur tolérance aux dommages. Dans un premier temps, un dialogue essai-calcul pour des sollicitations uniaxiales de traction simple sur composite stratifiés lisses, troués (plusieurs diamètres) et entaillés est mis en place. En utilisant différentes méthodes de suivi expérimental insitu (corrélation d'images, thermographie infrarouge) et post-mortem (micro-tomographie aux rayons-X), les scénarios de ruptures sont identifiés et comparés à ceux déterminés par simulation numérique « Discrete Ply Model ». Le modèle numérique est démontré valide pour simuler les cas étudiés (traction uniaxiale). Les influences de plusieurs paramètres du modèle sont étudiées dont la taille de maille et la présence de fissures discrètes. Dans un second temps, une étude expérimentale des stratifiés entaillés soumis à des sollicitations combinées à l'échelle supérieure (détail structural) est menée à l'aide du montage VERTEX conçu spécifiquement pour ces travaux. La modélisation de ce type d'essai est amorcée sur une plaque en aluminium pour valider la méthodologie de transfert de conditions limites obtenues par corrélation d'images. Cette stratégie est ensuite appliquée à un des drapages composite étudiés pour modéliser plusieurs types de sollicitations pour valider le « Discrete Ply Model » sur des cas de charge supplémentairesComposite structures sensitivity to substantial damage around notches leads us to assess their damage tolerance. First, both experiments and numerical simulations are being performed on small coupons under uniaxial tension for different configurations (plain, open-hole With different diameters and U-notch specimens). Using different methods of in situ experimental monitoring (image correlation, infrared thermography) and post-mortem micro-tomography (X-ray), failure scenarios are identified and compared to those determined by numerical simulations. The "Discrete Ply Model" is then proven valid to simulate the cases studied (uniaxial tension). The influences of several parameters such as mesh size and the presence of discrete cracks are investigated. Second, an experimental study of notched laminates subjected to complex loadings (structural detail scale) is conducted With the VERTEX rig, designed specifically for this work. Then, simulating this ype of tests is initiated on an aluminum plate to validate the methodology of boundary conditions (obtained by image correlation) transfer. This strategy is then applied to a notched laminated composite to validate the "Discrete Ply Model" on additional loading cases
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Ribeiro, Marcelo Leite. "Damage and progressive failure analysis for aeronautic composite structures with curvature." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/18/18148/tde-18112013-140301/.
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Recent improvements in manufacturing processes and materials properties associated with excellent mechanical characteristics and low weight have became composite materials very attractive for application on civil aircraft structures. However, even new designs are still very conservative, because the composite structure failure phenomena are very complex. Several failure criteria and theories have been developed to describe the damage process and how it evolves, but the solution of the problem is still open. Moreover, modern manufacturing processes, e.g. filament winding, have been used to produce a wide variety of structural shapes. Therefore, this work presents the development of a damage model and its application to simulate the progressive failure of flat composite laminates as well as for composite cylinders made by filament winding process. The proposed damage model has been implemented as a UMAT (User Material Subroutine) and VUMAT (User Material Subroutine for explicit simulations), which were linked to ABAQUSTM Finite Element (FE) commercial package. Progressive failure analyses have been carried out using FE Method in order to simulate the failure of filament wound composite structures under different quasi-static and impact loading conditions. In addition, experiments have been performed not only to identify parameters related to the material model but also to evaluate both the potentialities and the limitations of the proposed model.As recentes melhorias nos processos de fabricação e nas propriedades dos materiais associadas a excelentes características mecânicas e baixo peso tornam os materiais compósitos muito atrativos para aplicação em estruturas aeronáuticas. No entanto, mesmo novos projetos, ainda são muito conservadores, pois os fenômenos de falha dos compósitos são muito complexos. Vários critérios e teorias de falha têm sido desenvolvidos para descrever o processo de dano e sua evolução, mas a solução do problema ainda está em aberto. Além disso, técnicas modernas de fabricação, como o enrolamento filamentar (filament winding) vêm sendo utilizadas para produzir uma ampla variedade de formas estruturais. Assim, este trabalho apresenta o desenvolvimento de um modelo de dano e a sua aplicação para simular a falha progressiva de estruturas planas e cilíndricas fabricadas em material compósito através do processo de filament winding. O modelo de dano proposto foi implementado como sub-rotinas em linguagem FORTRAN (UMAT-User Material Subroutine e, VUMAT-User Material Subroutine para simulações explícitas), que foram compiladas junto ao programa comercial de Elementos Finitos ABAQUSTM. Várias análises numéricas foram realizadas via elementos finitos, a fim de prever a falha dessas estruturas de material compósito sob diferentes condições de carregamentos quase-estáticos e de impacto. Além disso, vários ensaios experimentais foram realizados, a fim de identificar os parâmetros relacionados com o modelo de material, bem como avaliar as potencialidades e as limitações do modelo proposto.
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Zhang, Chao. "Mechanical behavior of tubular composite structures." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1627489300935781.
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Nader, Jacques Walid. "Probabilistic Finite Element Analysis and Size Effects of Polymer Matrix Marine Grade Composites." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/NaderJW2007.pdf.
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Schclar, Noemi Alejandra. "Application of the Boundary Element Method to the structural analysis of three dimensional anisotropic material." Thesis, University of Portsmouth, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334408.
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Schneider, Christof. "Recyclable self-reinforced ductile fiber composite materials for structural applications." Doctoral thesis, KTH, Lättkonstruktioner, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-174131.
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Lightweight structures in vehicles are a proven way to reduce fuel consumption and the environmental impact during the use. Lower structural weight can be achieved by using high performance materials such as composites or using the material efficiently as a sandwich structure. Traditional composite materials such as carbon or glass fiber reinforced polymers have high weight specific mechanical properties but are inherently brittle and expensive. They consist of at least two different materials making recycling a difficult endeavor.The best composite material would have good weight specific properties and is ductile, cheap and comprises of a reinforcement and matrix material based on the same recyclable material making recycling easy. In self-reinforced polymer (SrP) composite materials, reinforcing fibers and matrix material are based on the same recyclable thermoplastic polymer making recycling to a straightforward process. SrP composite materials are ductile, inexpensive and have a high energy absorption potential. The aim of this thesis is to investigate the potential of SrP composites in structural applications. Firstly, the quasi-static and dynamic tensile and compression properties of a self-reinforced poly(ethylene terephthalate) (SrPET) composite material are investigated confirming the high energy absorption potential. Sandwich structures out of only SrPET with a lattice core are manufactured and tested in quasi-static out-of-plane compression showing the potential of SrPET as core material. Corrugated sandwich structured out of only SrPET are manufactured and tested in out-of-plane compression over a strain rate range10−4 s−1 - 103 s−1. The corrugated SrPET core has similar quasi-static properties as commercial polymeric foams but superior dynamic compression properties. Corrugated sandwich beams out of only SrPET are manufactured and tested in quasi-static three-point bending confirming the high energy absorption potential of SrPET structures. When comparing the SrPET beams to aluminum beams with identical geometry and weight, the SrPET beams shows higher energy absorption and peak load. The experimental results show excellent agreement with finite element predictions. The impact behaviorof corrugated SrPET sandwich beams during three-point bending is investigated. When comparing SrPET sandwich beams to sandwich beams with carbon fiber face sheets and high performance thermoset polymeric foam with the same areal weight, for the same impact impulse per area, the SrPET shows less mid-span deflection.QC 20151012
ECO2
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Seon, Guillaume. "Finite element-based failure models for carbon/epoxy tape composites." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28117.
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Kim, Joun S. "A Comparison Study of Composite Laminated Plates With Holes Under Tension." DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1895.
Full textAbstract:
A Comparison Study of Composite Laminated Plates with Holes under Tension
A study was conducted to quantify the accuracy of numerical approximations to deem sufficiency in validating structural composite design, thus minimizing, or even eliminating the need for experimental test. Error values for stress and strain were compared between Finite Element Analysis (FEA) and analytical (Classical Laminated Plate Theory), and FEA and experimental tensile test for two composite plate designs under tension: a cross-ply composite plate design of [(0/90)4]s, and a quasi-isotropic layup design of [02/+45/-45/902]s, each with a single, centered hole of 1/8” diameter, and 1/4" diameter (four sets total). The intent of adding variability to the ply sequences and hole configurations was to gauge the sensitivity and confidence of the FEA results and to study whether introducing enough variability would, indeed, produce greater discrepancies between numerical and experimental results, thus necessitating a physical test. A shell element numerical approximation method through ABAQUS was used for the FEA.
Mitsubishi Rayon Carbon Fiber and Composites (formerly Newport Composites) unidirectional pre-preg NCT301-2G150/108 was utilized for manufacturing—which was conducted and tested to conform to ASTM D3039/D3039M standards.
A global seed size of 0.020, or a node count on the order of magnitude of 30,000 nodes per substrate, was utilized for its sub-3% error with efficiency in run-time.
The average error rate for FEA strain from analytical strain at a point load of 1000lbf was 2%, while the FEA-to-experimental strains averaged an error of 4%; FEA-to-analytical and FEA-to-tensile test stress values at 1000lbf point load both averaged an error value of 6%. Suffice to say, many of these strain values were accurate up to ten-thousandths and hundred-thousandths of an in/in, and the larger stress/strain errors between FEA and test may have been attributed to the natural variables introduced from conducting a tensile test: strain gauge application methods, tolerance stacks from load cells and strain gauge readings.
Despite the variables, it was determined that numerical analysis could, indeed, replace experimental testing. It was observed through this thesis that a denser, more intricate mesh design could provide a greater level of accuracy for numerical solutions, which proves the notion that if lower error rates were necessitated, continued research with a more powerful processor should be able to provide the granularity and accuracy in output that would further minimize error rates between FEA and experimental. Additionally, design margins and factors of safety would generally cover the error rates expected from numerical analysis.
Future work may involve utilizing different types of pre-preg and further varied hole dimensions to better understand how the FEA correlates with analytical and tensile test results. Other load types, such as bending, may also provide insight into how these materials behave under loading, thus furthering the conversation of whether numerical approximations may one day replace testing all together.
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Ebrahimi-Looyeh, Mo. "Finite element simulation of heat flow in decomposing polymer composites." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4566/.
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Polymer composite materials, particularly glass reinforced plastics (GRP), are increasingly being used in the offshore industry and their behaviour in fire is studied using mathematical and numerical modelling. A generalised finite element method is developed to analyse the thermally induced response of a widely used GRP, consisting of polyester resin and glass fibre reinforcement. GRP panels, pipes and joins subject to hydrocarbon fires (i.e. high temperatures) are studied. One- and two-dimensional mathematical models are developed to study the fire performance of: (i) single-skinned GRP panels, (ii) twin-skinned GRP-Vermiculux sandwich panels, and (iii) thin and thick GRP joins (step panels). The models involve thermochemical decomposition of the material (pyrolysis) and include: (i) transient heat conduction, (ii) gas mass movement and internal heat convection of pyrolysis gases, (iii) mass loss and Arrhenius rate decomposition of the resin material into gases and char, and (iv) endothermicity of pyrolysis. The effect of imperfect bonding on heat transfer in sandwich panels and the accumulation of pyrolysis gases and internal pressurisation in thick step panels are also included. The models may be used with any combination of steady or time-dependent boundary conditions including temperature, radiation, chemical reactions, mass diffusion and free and forced convections. Various positions of panels, i.e. vertical, horizontal and inclined are studied. The material is assumed homogeneous and orthotropic with respect to thermal and transport properties which may vary with temperature, pore pressure and moisture. The finite element models use weighted residual approach with linear elements for one- dimensional and quadrilateral elements for two-dimensional. Non-linear terms and coefficients are evaluated explicitly using an iterative-updating method and nodal temperatures and pore pressures implicitly using Crank-Nicolson solution. The classical finite difference time stepping algorithm is used where an efficient solution is achieved using variable time step. Numerical results are presented in the form of temperature versus time, temperature versus distance, pore pressure versus distance, mass loss versus distance and moisture versus distance and compared with experimental data where available. It is shown that the decomposition of the material, endothermicity of pyrolysis and the movement of pyrolysis gases make substantial contributions towards the cooling behaviour and delaying the bum-through. The effect of gas mass movement and surface chemical reactions across the boundary layer adjacent to the fire-exposed surface is very important in introducing a theoretical boundary condition. An investigation into the effect of inclusion the variable thermal properties reveals considerable improvement in thermal predictions. Sandwich panels consisting of GRP/Vermiculux/GRP offer good thermal insulation. Thermal contact resistance at an imperfect bonding is important where an average difference of 12% can be found between the thermal responses of sandwich panels with perfect and imperfect bonding. For thin GRP step panels, a one-dimensional solution is found adequate to predict the fire resistance behaviour of the material. For thick GRP step panels, the effect of internal pressurisation coupled with temperature on the thermal response is considerable.
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Kaymak, Yalcin. "A Composite Frame/joint Super Element For Structures Strengthened By Externally Bonded Steel/frp Plates." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1052547/index.pdf.
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A materially non-linear layered beam super element is developed for the analysis of RC beams and columns strengthened by externally bonded steel/FRP plates. The elasto-plastic behavior of RC member is incorporated by its internally generated or externally supplied moment-curvature diagram. The steel plate is assumed to be
elasto-plastic and the FRP laminate is assumed to behave linearly elastic up to
rupture. The thin epoxy layer between the RC member and the externally bonded lamina is simulated by a special interface element which allows for the changing failure modes from steel plate yielding/FRP plate rupture to separation of the bonded plates as a result of bond failure in the epoxy layer. An empirical failure criterion based on test results is used for the epoxy material of the interface.
The most critical aspect of such applications in real life frame structures is the anchorage conditions at the member ends and junctions. This has direct influence on the success and the effectiveness of the application. Therefore, a special corner piece anchorage element is also considered in the formulation of the joint super
element, which establishes the fixity and continuity conditions at the member ends
and the joints.
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Baskin, Cem Ismail. "Finite Element Analysis Of Composite Laminates Subjected To Axial &." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12604975/index.pdf.
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This thesis focuses on the investigation of behavior of thick and moderately thick laminates under transverse and horizontal loading for different boundary conditions and configurations. An efficient finite element solution is proposed for analyzing composite laminates. Based on a combination of composite theory and 3-D Elasticity Theory, a 3-D finite element program is developed in MATLAB for calculating the stresses, strains and deformations of composite laminates under transverse and/or horizontal loading for different boundary conditions. The applicability of the formulation to analysis of laminated rubber bearings is also examined in this study. Since it is very important to calculate the correct stress state when developing models for composite behavior, the 3-D Elasticity Theory is used in this research. Numerical results are presented for various problems with different lamination schemes, loading and boundary conditions. In order to verify the analysis and the numerical calculations, numerical solutions obtained in this study are compared with available closed form solutions in the literature, experiment results and a commercial finite element program, namely ANSYS. The results obtained using the present finite element is found to be in acceptable and good agreement with the closed form solutions in the literature for thick and moderately thick rectangular and square plates.
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Vakiener, Adam R. "Preliminary investigation of flange local buckling in pultruded wide flange structural shapes." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/19562.
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Dharmawan, Ferry, and ferry dharmawan@rmit edu au. "The Structural Integrity And Damage Tolerance Of Composite T-Joints in Naval Vessels." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20081216.163144.
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In this thesis, the application of composite materials for marine structures and specifically naval vessels has been explored by investigating its damage criticality. The use of composite materials for Mine Counter Measure Vessels (MCMVs) was desirable, especially for producing material characteristics, such as light weight, corrosion resistance, design flexibility due to its anisotropic nature and most importantly stealth capability. The T-Joint structure, as the primary connection between the hull and bulkhead forms the focus of this research. The aim of the research was to determine the methodology to predict the damage criticality of the T-Joint under a pull-off tensile loading using FE (Finite Element) based fracture mechanics theory. The outcome of the research was that the Finite Element (FE) simulations were used in conjunction with fracture mechanics theory to determine the failure mechanism of the T-Joint in the presence of disbonds in the critical loca tion. It enables certain pre-emptive strengthening mechanisms or other preventive solutions to be made since the T-Joint responses can be predicted precisely. This knowledge contributes to the damage tolerance design methodology for ship structures, particularly in the T-Joint design. The results comparison between the VCCT (Virtual Crack Closure Technique) analysis and the experiment results showed that the VCCT is a dependable analytical method to predict the T-Joint failure mechanisms. It was capable of accurately determining the crack initiation and final fracture load. The maximum difference between the VCCT analysis with the experiment results was approximately 25% for the T-Joint with a horizontal disbond. However, the application of the CTE (Crack Tip Element) method for the T-Joint displayed a huge discrepancy compared with the results (fracture toughness) obtained using the VCCT method, because the current T-Joint structure geometry did not meet the Classical Laminate Plate Theory (CLPT) criteria. The minimum fracture toughness difference for both analytical methods was approximately 50%. However, it also has been tested that when the T-Joint structure geometry satisfied the CLPT criteria, the maximum fracture toughness discrepancy between both analytical methods was only approximately 10%. It was later discovered from the Griffith energy principle that the fracture toughness differences between both analytical methods were due to the material compliance difference as both analytical methods used different T-Joint structures.
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Almeida, Felipe Schaedler de. "Desenvolvimento de ferramentas computacionais para análise de interação fluido-estrutura incluindo não linearidade geométrica." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/76146.
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Esse trabalho trata da análise computacional de problemas aeroelásticos. Os casos de interesse envolvem escoamentos compressíveis em torno de estruturas de cascas de materiais compósitos laminados. A solução do problema de interação fluido- estrutura é conduzida por meio do esquema particionado denominado improved serial staggered procedure (ISS), o que permite a utilização de algoritmos independentes para a análise de cada componente do sistema. Um elemento triangular plano com três nós destinado à análise de cascas de materiais compósitos laminados é obtido com base na formulação de dois elementos de alta performance desenvolvidos para a análise de membranas e de placas. A flexibilidade ao corte transversal, a ausência de travamento por razão de aspecto em problemas com flexão no plano da casca são características do elemento. A análise dinâmica não linear é realizada através do procedimento corrotacional de conservação aproximada de energia (AECCP) que foi implementado com base na formulação corrotacional independente de elemento (element independent CR formulation – EICR). Essa abordagem permite que problemas transientes com grandes rotações e forte não linearidade geométrica sejam integrados por longos períodos de tempo, mantendo a estabilidade, a precisão e a eficiência da solução. A simulação do escoamento é realizada através do método explícito de Taylor-Galerkin de dois passos utilizando elementos finitos tetraédricos em malhas não estruturadas para a discretização espacial. As equações governantes do escoamento são dadas segundo a formulação lagrangeana-euleriana arbitrária (ALE), permitindo que malhas móveis sejam empregadas na análise dos problemas aeroelásticos. Um método simples e eficiente é adotado para a movimentação da malha do fluido com base na distância do nó às superfícies de contorno do escoamento. A utilização de malhas não coincidentes na discretização do fluido e da estrutura é possibilitada pelo emprego do esquema de projeção nodal para a transferência de informações entre os meios na região de interface. A apresentação, implementação e verificação de cada componente da ferramenta de análise é realizada independentemente graças à natureza do esquema de solução particionado. Por fim são analisados problemas de interação fluido-estrutura, onde as respostas obtidas são comparadas com resultados experimentais e numéricos de outros autores. Também são propostos e analisados novos problemas envolvendo estruturas de compósitos laminados.This work deals with computational analysis of aeroelastic problems, specifically those related to compressible flows around laminated composite shell structures. The fluid- structure problem is solved by a partitioned scheme called improved serial staggered procedure (ISS), allowing to use independent algorithms for the analysis of each system component. A 3-node triangular flat element for laminated composite shells is obtained based on the formulation of two high performance plate and membrane elements. Shear flexibility and no aspect ratio locking on in-plane bending problems are some of the element characteristics. The nonlinear dynamic analysis is performed using the approximately energy conserving corotational procedure (AECCP), which is implemented based on the element independent corotational formulation (EICR). This approach enables long time transient problems with strong nonlinearities and large rotations to be efficiently solved while keeping stability and accuracy. The flow simulation is performed by the explicit two step Taylor-Galerkin method employing tetrahedral finite elements in unstructured meshes for the space discrezation. The flow governing equations are given in arbitrary lagrangian-eulerian formulation, enabling aeroelastic simulations with moving meshes. A simple and efficient method is adopted to move the fluid mesh based on the distance of each node to the boundary surfaces. Transference of information between non-matching fluid and structure meshes are performed by the node-projection scheme. Each component of the aeroelastic analysis tool is independently presented, implemented and verified due to the partitioned nature of the scheme adopted for the solution of the coupled system. Some aeroelastic problems are analyzed and results are compared to other experimental and numerical works. New problems of aeroelastic analysis of laminated composite structures are proposed and solved.
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Medeiros, Ricardo de. "Development of a criterion for predicting residual strength of composite structures damaged by impact loading." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18148/tde-26072016-221608/.
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Advanced aerospace materials, including fibre reinforced polymer and ceramic matrix composites, are increasingly being used in critical and demanding applications, challenging not only the current damage prediction, detection, and quantification methodologies, but also the residual life of the structure. The main objective of this work consists of developing theoretical and experimental studies about residual strength for composite structures, which are damaged by impact loading, aided by a SHM system, which combines different methods. For this, it is necessary: to identify, and to localize damage, as well as to calculate the severity of the damage and to predict the residual strength of the composite structure. To achieve these goals, the research methodology should consider three methods: (1) Vibration Based Method (VBM); (2) Shearography Speckle (SS) and (3) Flexural After Impact (FAI). Composite plates, made of epoxy resin reinforced by carbon or glass fibre, are evaluated. Firstly, VBM provide Frequency Response Functions to be analysed by suitable metrics (including a new metric), which are compared in terms of their capability for damage identification and global location. Afterwards, the extension of impact damage is determined by using shearography speckle. This technique has demonstrated great potential for damage detection in composite laminated structures. The identification of the damage from the measurements performed with the SS technique is based on the analysis of disturbances in the speed field caused because of the different properties of the material. These abnormal deformations can be verified as typical strains in damaged structures. SS is a laser interferometry method sensitive to displacement gradient in a surface direction out of the plane. Under the action of a smaller load, the structure is deformed and the presence of damage is shown through local peculiarities of surface deformation observed field. Finally, a flexure after impact (FAI) test is used to evaluate its limitations and potentialities as a damage tolerance technique. The residual flexural strength of damaged specimens is evaluated by quasi-static four-point bending test. A new criterion based on a relationship between damage metric from VBM and FAI analysis is presented and discussed. Thus, these results are normalized by using the maximum load and the metrics for damage analyses, i.e. if there is no damage in the structure, then the metric returns zero value. If the structure is partially damaged then the metric returns a number between one and zero. In addition, if the structure is totally damaged (i.e. residual strength is lower than specified in design), then the metric returns a value equal one. Finally, it is discussed the advantages and limitations of this combination into the context of SHM system (Structural Health Monitoring System).Materiais compósitos estão cada vez mais sendo usados em aplicações críticas e exigentes, desafiando não apenas as metodologias atuais de previsão de dano, detecção, quantificação, mas também da vida residual da estrutura. O principal objetivo deste trabalho consiste no desenvolvimento de estudos teóricos e experimentais sobre a resistência residual de estruturas de compósito, que são danificadas pelo carregamento de impacto, auxiliado por um sistema SHM, que combina diferentes métodos. Para isso, é necessário: identificar, localizar danos, bem como determinar a severidade dos danos e estimar a resistência residual da estrutura. Para atingir esses objetivos, a metodologia de pesquisa considerou três métodos: (1) Método baseado em vibração; (2) Shearography Speckle (SS) e (3) Flexão após Impacto (FAI). Placas de compósito, fabricadas em resina epóxi reforçada por fibra de carbono ou de vidro, são avaliadas. Em primeiro lugar, o método baseado em vibração produz Funções de Resposta em Frequência, que são analisadas através de métricas adequadas (incluindo uma nova métrica), que são comparadas em termos de sua capacidade de identificação de danos e de localização global. Depois disso, a extensão de danos causados pelo impacto é determinada empregando SS. Esta técnica tem demonstrado grande potencial na detecção de dano em estruturas laminadas compósito. A identificação do dano a partir das medidas realizadas com a técnica SS tem por base a análise das perturbações no campo de curvaturas causada devido à heterogeneidade das propriedades do material. Estas deformações anormais podem ser verificadas como deformações típicas de estruturas danificadas. A SS é um método de interferometria laser sensível ao gradiente de deslocamento de uma superfície na direção fora do plano. Sob a ação de um pequeno carregamento, a estrutura é deformada e a presença de danos é revelada através de singularidades locais do campo de deformação observado na superfície. Finalmente, teste de flexão após o impacto (FAI) é usado para avaliar suas limitações e potencialidades como uma técnica de tolerância ao dano. A resistência à flexão das amostras intactas e danificadas é avaliada por ensaio de flexão em quatro-pontos quase-estático. Um novo critério baseado em uma relação entre a métrica de dano prevista pelos métodos de vibração e a análise via FAI é apresentado e discutido. Assim, estes resultados são normalizados utilizando a carga máxima e as métricas de dano, ou seja, se não houver nenhum dano na estrutura, a métrica retorna valor igual a zero. Se a estrutura é parcialmente danificada, a métrica retorna um valor entre um e zero. Além disso, se a estrutura está totalmente danificada (ou seja, a resistência residual está abaixo do especificado em projeto), a métrica retorna um valor igual a um. Por fim, discutem-se as vantagens e limitações desta combinação para o contexto de sistema SHM (Sistema de Monitoramento da Integridade Estrutural).
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Widjaja, Budi R. "Analytical investigation of composite diaphragms strength and behavior." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-07112009-040307/.
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Jung, Se-Kwon. "Inelastic Strength Behavior of Horizontally Curved Composite I-Girder Bridge Structural Systems." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11618.
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This research investigates the strength behavior of horizontally curved composite I-girder bridge structural systems, and the representation of this behavior by the AASHTO (2004b) LRFD provisions. The primary focus is on the design of a representative curved composite I-girder bridge tested at the FHWA Turner-Fairbank Highway Research Center, interpretation of the results from the testing of this bridge, including correlation with extensive linear and nonlinear finite element analysis solutions, and parametric extension of the test results using finite element models similar to those validated against the physical tests. These studies support the potential liberalization of the AASHTO (2004b) provisions by the use of a plastic moment based resistance, reduced by flange lateral bending effects, for composite I-girders in positive bending.
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Quintanas, Corominas Adrià. "Towards a high-performance computing finite element simulation framework for virtual testing of composite structures." Doctoral thesis, Universitat de Girona, 2019. http://hdl.handle.net/10803/669323.
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his doctoral thesis aims at developing and implementing a computational framework for performing virtual testing of composite structures using a High-Performance Computing (HPC) environment. In this sense, this thesis presents several novel constitutive models based on the continuum damage mechanics theory and their implementation in the HPC-base Finite Element (FE) simulation code called Alya. The verification and validation of the models are performed comparing the numerical predictions with analytical formulations and experimental data. The comparisons demonstrate not only the reliability of the damage models but also the potential of an HPC-based environment for Virtual Testing of COmposite STructures. Therefore, the outcome of this thesis is both the formulation of new fracture models and the numerical framework named Alya-VITECOSTL’objectiu d’aquesta tesis doctoral és el desenvolupament i implementació d’un marc computacional d’alt rendiment (HPC, de les sigles en anglès de High Performance Computing) amb el fi de realitzar proves virtuals d’estructures fetes de materials compòsits. En aquest sentit, aquesta tesis presenta la formulació de diversos models constitutius basats en la teoria de la mecànica de danys continus així com la seva implementació en el codi de simulació HPC anomenat Alya. La verificació i validació dels models i la seva implementació es realitza comparant les prediccions numèriques amb solucions analítiques i dades experimentals. Els resultats demostren la fiabilitat dels models formulats així com el potencial i avantatges oferts pels codis de simulació HPC. Per tant, el resultat d’aquesta tesis és tant la formulació dels models de dany progressiu com el marc numèric de simulació anomenat Alya-VITECOST.
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Navale, Kunal. "FINITE ELEMENT SIMULATION OF REPAIR OF DELAMINATED COMPOSITE STRUCTURES USING PIEZOELECTRIC LAYERS." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3119.
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Damage in composite material fabricated aerospace, aeronautical, mechanical, civil and offshore structures often results from factors such as fatigue, corrosion and accidents. Such damage when left unattended can grow at an alarming rate due to the singularity of the stress and strain in the vicinity of the damage. It can lead to increase in the vibration level, reduction in the load carrying capacity, deterioration in the normal performance of the component and even catastrophic failure. In most conditions, the service life of damaged components is extended with repair instead of immediate replacement. Effective repair of structural damage is therefore an important and practical topic. Repair can extend the service life and can be a cost efficient alternative to immediate replacement of the damaged component. Most conventional repair methods involve welding, riveting or mounting additional patches on the parent structure without removing the damaged portion. These methods tend to be passive and inflexible, faced with the limitations of adjusting the repair to the changes in external loads.Besides, in certain cases these methods may lead to additional damage to the structure. For example, the in-situ drilling required in some cases can cause damage to items such as hidden or exposed hydraulic lines and electrical cables. Welding or bonding patches can cause significant stress alterations and serious stress corrosion problems, apart from burdening the weight sensitive structures. Above all, effective repair applying conventional analytical methods hinges on calculation of the singularity of stress and strain in the vicinity of the damage, which is be a difficult as only approximate solutions are available. Thus, a need is felt to update the repair methods with the advancement in fields of materials, sensing and actuating. This can make the repair more effective and efficient than conventional repair methodology. Current research proposes the use of piezoelectric materials in repair of delaminated composite structures. A detailed mechanics analysis of the delaminated beams, subjected to concentrated static loads and axial compressive loads, is presented. The discontinuity of shear stresses induced at delamination tips due to bending of the beams, under action of concentrated static load and axially compressive load, is studied. This discontinuity of the shear stresses normally leads to the sliding mode of fracture of the beam structures. In order to ensure proper functioning of these beam structures, electromechanical characteristics of piezoelectric materials are employed for their repair. Numerical simulations are conducted to calculate the repair voltage to be applied to the piezoelectric patches to erase the discontinuity of horizontal shear stress at the delamination tips and thus, render the beam repaired. The variation of repair voltage with location and size of the delamination is considered. FE simulations are performed to validate the numerically calculated voltage values. The research presented serves to provide information on the design of piezoelectric materials for the repair of delaminated composite structures.M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering
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Chakravarty, Uttam Kumar. "Section builder: a finite element tool for analysis and design of composite." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22640.
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Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2008.Committee Chair: Bauchau, Olivier; Committee Member: Craig, James; Committee Member: Hodges, Dewey; Committee Member: Mahfuz, Hassan; Committee Member: Volovoi, Vitali.