Thermomechanical Behavior of Dissipative Composite Materials

George Chatzigeorgiou, Nicholas Charalambakis, Yves Chemisky, Fodil Meraghni

• Publisher: ISTE Press - Elsevier
• Year: 2018
• Print ISBN: 9781785482793
• eBook ISBN: 9780081025529
• Topic: Tecnologia e ingegneria
• Subtopic: Scienza dei materiali

Thermomechanical Behavior of Dissipative Composite Materials presents theoretical and numerical tools for studying materials and structures under fully coupled thermomechanical conditions, focusing primarily on composites. The authors cover many aspects of the modeling process and provide the reader with the knowledge required to identify the conservation laws and thermodynamic principles that must be respected by most solid materials. The book also covers construct constitutive laws for various types of dissipative processes, both rate-independent and rate-dependent, by utilizing a rigorous thermodynamic framework. Topics explored are useful for graduate students and advanced researchers who wish to strengthen their knowledge of the application of thermodynamic principles. - Identifies the conservation laws and thermodynamic principles that need to be respected by any solid material - Presents construct, proper constitutive laws for various types of dissipative processes, both rate-independent and rate-dependent, by utilizing an appropriate thermodynamic framework - Includes robust numerical algorithms that permit accuracy and efficiency in the calculations of very complicated constitutive laws - Uses rigorous homogenization theories for materials and structures with both periodic and random microstructure

Foreword 1

This book, by Dr. George Chatzigeorgiou, Dr. Nicolas Charalambakis, Dr. Yves Chemisky and Prof. Fodil Meraghni, deals with composite materials and their complex mechanical behavior. It takes an important new position among the current literature, often very specialized, existing in this domain.

The authors are well-recognized scientists in the materials community and experienced mechanicians, researchers and teaching researchers. They have worked for many years on these materials, used in all domains of industry, particularly in the automotive and aeronautical industry. We can additionally mention their integration within the LEM3 Laboratory, University of Lorraine, Arts et Métiers and CNRS, a Laboratory of Excellence within the Materials Community with Worldwide recognition.

After a general introductory chapter on the notations and continuum mechanics theory they will use, the authors propose a summary of the numerical methods useful for engineers. They then show how composite materials, integrating useful but complex heterogeneities, must be dealt with in mechanics theory. They then focus on periodic and random reinforcements composite behavior, for which the homogenization techniques enable changing scales in a rational manner. This provides the knowledge of the desired macroscopic mechanical properties of a given microstructure, but also the analysis of the local phenomena induced by an external mechanical load on the structure.

This book is rigorously written and includes the latest scientific developments. It proposes a simple and complete view of the existing knowledge of the mechanical behavior of these materials, and is suitable for students and engineers seeking to familiarize themselves with the mechanics of composite materials, and develop complex, optimized and light-weighted structures.

Prof. Yves Rémond, University of Strasbourg - CNRS

Foreword 2

The art of mixing heterogeneous materials to improve the bulk properties of mixtures, such as stiffness and strength, has been refined over thousands of years, especially for the civil and military needs of civilizations. During the last two centuries and since the industrial revolution, composite materials, synthetic and natural composites, have been widely used in transportation electronics and biomedical application, among others. The need to develop mathematical models to describe the macroscopic response of heterogeneous materials arose alongside advances in imaging methods that revealed microstructural characteristics contributing to their macroscopic response. In the case of metals, specialized heat treatments combined with other processing techniques led to the creation of desirable microstructures for optimal thermomechanical properties, while in polymeric, metallic and ceramic matrix composite materials, fiber volume fractions and their placement together with the selection of other processing parameters resulted in designing desirable macroscopic or effective bulk properties.

Scientists and engineers have tried to address two key questions related to macroscopic properties of heterogeneous materials: Given sufficient information about their microstructure, how can macroscopic or effective bulk properties of heterogeneous materials be accurately modeled; and, given desired macroscopic properties, how can optimal microstructures be chosen which result in such macroscopic properties. The upscaling process from the micro length scales, where microstructures are realizable to the macroscale, formed the forward homogenization problem that resulted in the development of various analytical and computational techniques over the last few decades. Averaging methods were developed to estimate the macroscopic thermomechanical properties of composites and other heterogeneous media with input of their constituents properties, their morphology and volume fractions. This effort initially focused on polycrystalline metals with heterogeneous precipitates during the middle of the 20th century, shifting to polymeric fibrous composites during the latter part of the century, resulting in what is widely accepted now as the field of micromechanics.

A key contribution that formed the mathematical basis for the development of micromechanics is the Eshelby solution, which is the fundamental elasticity solution of the elastic field surrounding an ellipsoidal inclusion, with a prescribed eigenstrain, embedded into an infinite elastic medium. Since its publication in 1957, and especially its application to heterogeneous media with an extension to what is now known as the Eshelby equivalence principle, many of the averaging upscaling methodologies for composites and heterogeneous microstructures are based on the Eshelby solution. In addition to averaging techniques, like the self-consistent and Mori-Tanaka methods, based on extensions of the Eshelby solution in order to account for particle interactions, computational methods have been developed for heterogeneous media with periodic microstructures, following analytical upscaling or homogenization methods, especially in estimating bounds on macroscopic properties. The use of multiple scales and asymptotic series over a representative volume element allowed for the development of rigorous formulations to be derived and in most cases numerical methods like finite elements to be effectively utilized.

The field of micromechanics is still very active today as new challenges arise from multifunctional materials with coupled properties, for example piezoelectric, electrostrictive, piezomagnetic and magnetostrictive, and especially when microstructure plays a critical role for multifunctional behavior, as is the case for most nanocomposites. An additional challenge is that field interactions in multifunctional heterogeneous materials, such as electromagnetic and thermomechanical, are nonlinear. Nonlinear dissipative heterogeneous materials bring an additional challenge due to path dependence of their macroscopic behavior and in some cases explicit time dependence. This necessitates the development of incremental formulations for the macroscopic response of history dependent heterogeneous materials. A serious effort to include some of the current methodologies and trends, especially the nonlinear behavior of heterogeneous dissipative materials and the necessary analytical and computational tools, is the focus of this book.

The authors follow a rigorous methodology that first introduces the conservation principles and the constitutive laws based on thermodynamics principles. The thermodynamic framework is structured in such a way that allows its direct implementation in homogenization techniques proposed for composites. The book also introduces the computational tools originally developed for homogeneous inelastic dissipative media, such as the return mapping algorithms, with an adaptation for the micromechanics techniques to be used for heterogeneous media. The authors address rigorously periodic homogenization, based on the asymptotic expansion method, for the fully coupled thermomechanical homogenization framework for dissipative materials. Later in the book, they also address the Eshelby-based micromechanical approaches for random media and their extension to fully coupled thermomechanical processes in dissipative composites.

Overall, the authors have developed a consistent formulation of the thermomechanical response of inelastic, history dependent constituents and they have incorporated it, using a multiscale homogenization formulation to estimate the macroscopic history dependent response of heterogeneous materials. They have also provided, along with the formulation, the necessary computational tools for the actual implementation. Graduate students and researchers in engineering sciences, applied mathematics and mechanics of materials, as well as many professionals developing new heterogeneous materials with desirable thermomechanical responses and energy dissipation capacity, will find this book a very useful companion, written by experts in the field.

Dimitris C. Lagoudas, Texas A&M University, USA

Preface

George Chatzigeorgiou; Nicolas Charalambakis; Yves Chemisky; Fodil Meraghni July 2017

The objective of this book is to present a consistent methodology for the study and numerical computation of the thermomechanical response of materials and structures, with a particular focus on composites. We recognize that there are plenty of studies in the literature that successfully treat, both theoretically and computationally, the thermomechanical response of various categories of dissipative materials or composites and that are not included in this manuscript. Our aim though is not to present an extensive review of these studies, but to propose to the scientific community a general framework for studying the vast majority of dissipative materials and composites under fully coupled thermomechanical loading conditions. We cover many aspects of the modeling process, so that the reader is able to find how to: (i) identify the conservation laws and thermodynamic principles that need to be respected by any solid material, (ii) construct proper constitutive laws for various types of dissipative processes, both rate-independent and rate-dependent, by utilizing an appropriate thermodynamic framework, (iii) design robust numerical algorithms that permit accuracy and efficiency in the calculations of very complicated constitutive laws, (iv) extend all the previous points to the study of composites, utilizing rigorous homogenization theories for materials and structures with both periodic and random microstructure. For the last point, the book explores the concepts of periodic homogenization, namely the asymptotic expansion homogenization method, as well as various micromechanics theories based on the Eshelby approach. We believe that our book, with the topics it covers, will be useful to both young and advanced researchers that want to obtain a general guide to properly studying the thermomechanical response of dissipative materials and composites, and to identifying robust and accurate computational schemes.

Chapter 1 is devoted to a quick presentation of tensor calculus, both in Cartesian and curvilinear coordinate systems, as well as the various symbols denoting tensor operations that are utilized throughout the book. While the indicial notation with the Einstein summation rule is very helpful in many situations, the large number of indices, mainly introduced in Chapter 3 on computational methods and Chapters 5 and 6 on homogenization theories, requires a more elegant representation of tensors. Thus, the tensorial notation with bold fonts for vectors and higher order tensors is chosen in the book. The first chapter also discusses the Voigt notation, which is particularly useful for representing second and fourth order tensors as vectors and matrices respectively, simplifying the computational procedures. In addition, a special notation for isotropic fourth order tensors is included in section 1.1.3.

Chapter 2 is a short summary of the continuum mechanics theory and the identification of constitutive laws based on thermodynamic principles. The first four sections discuss the general principles of continuum mechanics (kinetics, kinematics, conservation laws, thermodynamics) and their reduction when small deformation procedures are considered. The fifth section of the chapter focuses on the description of constitutive laws for dissipative materials using a proper thermodynamic framework. The presented framework is quite general in order to include many types of mechanisms: viscoelasticity, plasticity, viscoplasticity and continuum damage constitutive laws are discussed in this section. Even though not mentioned explicitly, the framework is also capable of describing phase transformation mechanisms, such as martensitic transformation occurring, for example, in shape memory alloys. The chapter closes with the presentation of a thermomechanical parameters identification strategy through appropriate experimental protocol for an elastoplastic material.

Chapter 3 presents rigorous integration methods that make it possible to identify and computationally simulate the response of materials and structures under quasi-static loading conditions when nonlinear mechanisms appear. The chapter introduces the general iterative scheme that can be applied for solving a boundary value problem using the finite element method (though without entering into details on finite element computations) and focuses mainly on the numerical implementation of the constitutive law for a homogeneous material. The presented methodologies are based on the well known return mapping algorithm scheme. Analytical description on the methods is given for the case of rate independent plasticity. Numerical applications in plasticity and viscoelasticity are also included in the chapter. The numerical procedures discussed here, even though applied to homogeneous materials, can be considered as the basis for the design of numerical algorithms applied to composites.

Chapter 4 introduces the notion of homogenization, which is presented in two different frameworks: one that focuses on homogenization from an engineering point of view, and one that describes the principles of mathematical homogenization. Both frameworks eventually lead to the same conclusions, even though they start from a different theoretical background. The engineering oriented homogenization accounts for composites with periodic or random microstructure and its concepts are mainly utilized in Chapter 6. On the other hand, the mathematical homogenization is the basis of the asymptotic expansion homogenization method that is utilized in Chapter 5 to describe the homogenization of composites with periodic microstructure.

Chapter 5 focuses on composite materials and structures with periodic microstructure. The asymptotic expansion homogenization method is employed for identifying the microscopic and macroscopic principles that the actual composite obeys (kinetics, kinematics, conservation laws, thermodynamics). For quasi-static processes and composites with dissipative material constituents a numerical scheme is proposed for solving the fully coupled thermomechanical problem iteratively and simultaneously in the two scales (microscopic and macroscopic). An illustrative example of multilayered composite material is discussed and various numerical applications with elastic, plastic and viscoplastic responses are presented.

Chapter 6 discusses homogenization techniques for composite materials and structures with random microstructure. The described methodologies belong to the mean field or Eshelby based theories. After presenting the classical Eshelby problems the chapter introduces three homogenization techniques: the Mori-Tanaka, the self consistent and the Ponte-Castañeda and Willis method. For quasi-static processes and composites with dissipative material constituents an iterati...

Table of contents

• Cover
• Title page
• Table of Contents
• Copyright
• Foreword 1
• Foreword 2
• Preface
• Nomenclature
• 1: Mathematical Concepts
• 2: Continuum Mechanics and Constitutive Laws
• 3: Computational Methods
• 4: Concepts for Heterogeneous Media
• 5: Composites with Periodic Structure
• 6: Composites with Random Structure
• Appendix 1: Average Theorems in Large Deformations
• Appendix 2: Periodic Homogenization in Large Deformations
• Bibliography
• Index