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Category :
Languages : en
Pages :

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ISBN:
Category :
Languages : en
Pages : 28

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A life prediction model is being developed by the authors for application to metal matrix composites (MMC's). The systems under study are continuous silicon carbide fibers imbedded in titanium matrix. The model utilizes a computationally based framework based on thermodynamics and continuum mechanics, and accounts for matrix inelasticity, damage evolution, and environmental degradation due to oxidation. The computational model utilizes the finite element method, and an evolutionary analysis of a unit cell is accomplished via a time stepping algorithm. The computational scheme accounts for damage growth such as fiber-matrix debonding, surface cracking, and matrix cracking via the inclusion of cohesive zone elements in the unit cell. These elements are located based on experimental evidence also obtained by the authors. The current paper outlines the formulation utilized by the authors to solve this problem, and recent results are discussed. Specifically, results are given for a four-ply unidirectional composite subjected to cyclic fatigue loading at 650°C both in air and inert gas. The effects of oxidation on the life of the composite are predicted with the model, and the results are compared to limited experimental results.

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Category :
Languages : en
Pages : 28

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Category :
Languages : en
Pages : 31

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The objective of the project was to develop a multiscale computational model capable of predicting the evolution of matrix cracking, delamination, and fiber cracking in viscoelastic composite structures subjected to ballistic impact. The model is three dimensional and computational in nature, utilizing the finite element method, and this model is being implemented to the explicit code DYNA3D. Crack growth is simulated via the cohesive zone model currently under development by the author. The cohesive zone model for predicting damage evolution in laminated composite plates is cast within a three dimensional continuum finite element algorithm capable of simulating the evolution of matrix, fiber, and delamination cracking in composite structures subjected to ballistic impact. Cracking on vastly differing length scales is accounted for by employing global-local techniques, with appropriate damage dependent homogenization techniques introduced to bridge the disparate scales. Finally, simplified generic example problems were solved analytically and compared to computational results obtained with the model as a means of model verification. A damage constitutive model for polymer-matrix composite materials was developed and implemented into a commercially available finite element package.

Author:
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Category : Aeronautics
Languages : en
Pages : 548

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Author: S.N. Atluri
Publisher: Springer Science & Business Media
ISBN: 3642796540
Category : Technology & Engineering
Languages : en
Pages : 3181

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AI!, in the earlier conferences (Tokyo, 1986; Atlanta, 1988, Melbourne, 1991; and Hong Kong, 1992) the response to the call for presentations at ICES-95 in Hawaii has been overwhelming. A very careful screening of the extended abstracts resulted in about 500 paper being accepted for presentation. Out of these, written versions of about 480 papers reached the conference secretariat in Atlanta in time for inclusion in these proceedings. The topics covered at ICES-95 range over the broadest spectrum of computational engineering science. The editors thank the international scientific committee, for their advice and encouragement in making ICES-95 a successful scientific event. Special thanks are expressed to the International Association for Boundary Elements Methods for hosting IABEM-95 in conjunction with ICES-95. The editors here express their deepest gratitude to Ms. Stacy Morgan for her careful handling of a myriad of details of ICES-95, often times under severe time constraints. The editors hope that the readers of this proceedings will find a kaleidoscopic view of computational engineering in the year 1995, as practiced in various parts of the world. Satya N. Atluri Atlanta, Georgia, USA Genki Yagawa Tokyo,Japan Thomas A. Cruse Nashville, TN, USA Organizing Committee Professor Genki Yagawa, University of Tokyo, Japan, Chair Professor Satya Atluri, Georgia Institute of Technology, U.S.A.

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Category : Aeronautics
Languages : en
Pages : 1148

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Category :
Languages : en
Pages : 0

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A micro-mechanical cyclic/fatigue damage model is developed for metal matrix composites. The model is based on thermodynamical principles within the framework of continuum damage mechanics and employs physical principles of damage behavior in metal matrix composites. A micro-mechanical approach is used in the sense that the overall material behavior is predicted by modeling the material behavior of the individual constituents. The Mori-Tanaka method is employed as a homogenization procedure. Individual anisotropic damage variables in the form of second order tensors are used for each of the constituents to allow for the modeling of appropriate damage and failure mechanisms in the composite. Individual damage initiation and evolution equations are developed for each constituent where physical principles of the damage mechanisms observed in experiments are considered. Damage mechanisms such as debonding and delamination are represented through individual damage tensors. The overall damage in the composite is obtained based on the individual damage tensors by means of the employed homogenization procedure. The elasto-plastic constitutive equations incorporate the influence of damage through the definition of the so-called damage effect tensors. A numerical implementation of the model is used to simulate cyclic/fatigue damage in metal matrix composites. Comparison of the results from the numerical simulations with experimental data show good agreement and substantiate the capabilities of the model.

Author: Yehia A. Bahei-El-Din
Publisher: Springer Science & Business Media
ISBN: 0306469359
Category : Technology & Engineering
Languages : en
Pages : 327

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The field of composite materials has seen substantial development in the past decade, New composite systems are being continually developed for various applications. Among such systems are metal, intermetallic, and superalloy matrix composites, carbon-carbon composites as well as polymer matrix composites. At the same time, a new discipline has emerged of active or smart materials, which are often constructed as composite or heterogeneous media and structures. One unifying theme in these diverse systems is the influence that uncoupled and coupled eigenfields or transformation fields exert on the various types of overall response, as well as on the respective phase responses. Problems of this kind are currently considered by different groups which may not always appreciate the similarities of the problems involved. The purpose of the IUTAM Symposium on Transformation Problems in Composite and Active Materials held in Cairo, Egypt from March 10 to 12, 1997 was to bring together representatives of the different groups so that they may interact and explore common aspects of these seemingly different problem areas. New directions in micromechanics research in both composite and active materials were also explored in the symposium. Specifically, invited lectures in the areas of inelastic behavior of composite materials, shape memory effects, functionally graded materials, transformation problems in composite structures, and adaptive structures were delivered and discussed during the three-day meeting. This book contains the printed contributions to the IUTAM Symposium.

Author:
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ISBN:
Category : Mechanics, Applied
Languages : en
Pages : 400

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