xviii Preface The integrated and system approach,ranging from microstructure to component net shape,offers almost unlimited opportunity in composites processing and manufacturing.The figure below depicts the interdependence of processing,microstructure,properties, responses to external fields (physical,chemical and mechanical), and performance of composites. Processing Materials Analysis and science science modeling Durability Processing Microstructure Property Responses to external fields Microstructure Responses to Property external fields Performance Design science Optimization The purpose of this book is to address the issue of designing the microstructure of composites for optimum performance.This is achieved through the selection of fiber and matrix materials as well as the placement of both continuous and discontinuous fibers in matrix materials.Continuous fibers can assume straight or wavy shapes;they can also be hybridized or woven into textile preforms. The wide range of microstructures available offers tremendous versatility in the performance of composites;the ability to design microstructures enables performance to be optimized. The book is intended as an intermediate-level textbook for students and a reference for research scientists and engineers. Readers need some background and preparation in materials science and applied mechanics.The first chapter examines the driving forces for advances in fiber composites,as well as the trends and opportunities of this rapidly developing field.Besides providing a concise summary of the linear elastic laminate theory,Chapter 2 examines some of the recent developments in the mechanics of laminated composites.Particular emphasis is given to thick lamin- ates,hygrothermal effects and thermal transient effects.Chapter 3 treats the strength of continuous-fiber composites.Analyses of the local load redistribution due to fiber breakages are presented first. They are followed by a fairly comprehensive treatment of the statistical tensile strength theories which encompasses the behavior of individual fibers,fiber bundles,unidirectional fiber composites
xviii Preface The integrated and system approach, ranging from microstructure to component net shape, offers almost unlimited opportunity in composites processing and manufacturing. The figure below depicts the interdependence of processing, microstructure, properties, responses to external fields (physical, chemical and mechanical), and performance of composites. Processing science Proc J 1 Micros essing \ tructure Materials science Microstructure crostructu Analysis and modeling Property Responses to external fields Durability Responses to external fields Performance Design science Optimization The purpose of this book is to address the issue of designing the microstructure of composites for optimum performance. This is achieved through the selection of fiber and matrix materials as well as the placement of both continuous and discontinuous fibers in matrix materials. Continuous fibers can assume straight or wavy shapes; they can also be hybridized or woven into textile preforms. The wide range of microstructures available offers tremendous versatility in the performance of composites; the ability to design microstructures enables performance to be optimized. The book is intended as an intermediate-level textbook for students and a reference for research scientists and engineers. Readers need some background and preparation in materials science and applied mechanics. The first chapter examines the driving forces for advances in fiber composites, as well as the trends and opportunities of this rapidly developing field. Besides providing a concise summary of the linear elastic laminate theory, Chapter 2 examines some of the recent developments in the mechanics of laminated composites. Particular emphasis is given to thick laminates, hygrothermal effects and thermal transient effects. Chapter 3 treats the strength of continuous-fiber composites. Analyses of the local load redistribution due to fiber breakages are presented first. They are followed by a fairly comprehensive treatment of the statistical tensile strength theories which encompasses the behavior of individual fibers, fiber bundles, unidirectional fiber composites
Preface xix cross-ply composites and laminates of multi-directional plies. Various modes of failure of laminated composites are examined. Section 3.4.6.2 is contributed by S.L.Phoenix,and Sections 3.4.7.4 and 3.4.8 are contributed by A.S.D.Wang.Chapter 4 deals with the elastic,physical and viscoelastic properties as well as the strength and fracture behavior of short-fiber composites.The effects of variations in fiber length and orientation are examined using a probabilistic approach.In Chapter 5,fiber hybridization serves as a vivid example of how the performance of composites can be controlled through the selection of material systems and their geometric distributions.The synergistic effects between the com- ponent phases with low elongation and high elongation fibers are of particular interest.Chapter 6 is devoted to two-dimensional textile structural composites based on woven,knitted and braided pre- forms.A comprehensive treatment of the techniques for analyzing and modeling the thermomechanical behavior of two-dimensional textile composites is presented.Chaper 7 introduces recent de- velopments in the processing of three-dimensional textile preforms based on braiding,weaving,stitching and knitting.The processing- microstructure relationship is demonstrated by the establishment of processing windows'for a specific forming technique.Then the microstructure-property relationship is exemplified through the construction of 'performance maps'.Mechanical properties of polymer-and metal-based composites using three-dimensional tex- tile preforms are reviewed.Chapters 8 and 9,in contrast to the earlier chapters,treat the topic of finite elastic deformation of flexible composites.The fundamental characteristics of flexible composites and the technique for analyzing them are presented in Chapter 8.A rigorous treatment of the constitutive relations of flexible composites is developed in Chapter 9 based upon both the Lagrangian and Eulerian descriptions of finite elastic deformation. Overall,the inter-relationship among processing,microstructure, property,responses to external fields,and performance of compos- ites is emphasized throughout this text. The contents of this book have evolved from my experience during two decades of teaching and research of composite materials at the University of Delaware.Stimulation from students and co-workers was indispensable to the preparation of this book.The contributions of the individuals with whom I had the privilege and pleasure to interact are too numerous to cite here.However,this book serves as a tribute to the intellectual achievements of them all. The generous support provided by the National Science Founda-
Preface xix cross-ply composites and laminates of multi-directional plies. Various modes of failure of laminated composites are examined. Section 3.4.6.2 is contributed by S. L. Phoenix, and Sections 3.4.7.4 and 3.4.8 are contributed by A. S. D. Wang. Chapter 4 deals with the elastic, physical and viscoelastic properties as well as the strength and fracture behavior of short-fiber composites. The effects of variations in fiber length and orientation are examined using a probabilistic approach. In Chapter 5, fiber hybridization serves as a vivid example of how the performance of composites can be controlled through the selection of material systems and their geometric distributions. The synergistic effects between the component phases with low elongation and high elongation fibers are of particular interest. Chapter 6 is devoted to two-dimensional textile structural composites based on woven, knitted and braided preforms. A comprehensive treatment of the techniques for analyzing and modeling the thermomechanical behavior of two-dimensional textile composites is presented. Chaper 7 introduces recent developments in the processing of three-dimensional textile preforms based on braiding, weaving, stitching and knitting. The processingmicrostructure relationship is demonstrated by the establishment of 'processing windows' for a specific forming technique. Then the microstructure-property relationship is exemplified through the construction of 'performance maps'. Mechanical properties of polymer- and metal-based composites using three-dimensional textile preforms are reviewed. Chapters 8 and 9, in contrast to the earlier chapters, treat the topic of finite elastic deformation of flexible composites. The fundamental characteristics of flexible composites and the technique for analyzing them are presented in Chapter 8. A rigorous treatment of the constitutive relations of flexible composites is developed in Chapter 9 based upon both the Lagrangian and Eulerian descriptions of finite elastic deformation. Overall, the inter-relationship among processing, microstructure, property, responses to external fields, and performance of composites is emphasized throughout this text. The contents of this book have evolved from my experience during two decades of teaching and research of composite materials at the University of Delaware. Stimulation from students and co-workers was indispensable to the preparation of this book. The contributions of the individuals with whom I had the privilege and pleasure to interact are too numerous to cite here. However, this book serves as a tribute to the intellectual achievements of them all. The generous support provided by the National Science Founda-
XX Preface tion,Department of Energy,Department of Transportation,Army Research Office,Office of Naval Research,Naval Research Labo- ratory,Air Force Office of Scientific Research,NASA,industrial companies and the Center for Composite Materials of the Univers- ity of Delaware for conducting the research reported in this book is greatly appreciated.Ding-Guey Hwang,Shen-Yi Luo,Joon-Hyung Byun and Wen-Shyong Kuo read the manuscript and gave critical comments.Te-Pei Niu,Yih-Cherng Chiang,Mark Deshon and Alison Gier provided valuable assistance in the preparation of the manuscript. Lastly,I should like to express my deep appreciation to the following persons.The late Prof.Alan S.Tetelman of Stanford University first pointed out to me the technological potential of fiber composites.As a colleague of mine at Delaware,Prof.R. Byron Pipes has greatly enriched my perspective on the subject matter.The scholarship and guidance of Prof.Anthony Kelly have always been a source of inspiration to me.Prof.Jerzy L.Nowinski encouraged me throughout the course of this endeavor
xx Preface tion, Department of Energy, Department of Transportation, Army Research Office, Office of Naval Research, Naval Research Laboratory, Air Force Office of Scientific Research, NASA, industrial companies and the Center for Composite Materials of the University of Delaware for conducting the research reported in this book is greatly appreciated. Ding-Guey Hwang, Shen-Yi Luo, Joon-Hyung Byun and Wen-Shyong Kuo read the manuscript and gave critical comments. Te-Pei Niu, Yih-Cherng Chiang, Mark Deshon and Alison Gier provided valuable assistance in the preparation of the manuscript. Lastly, I should like to express my deep appreciation to the following persons. The late Prof. Alan S. Tetelman of Stanford University first pointed out to me the technological potential of fiber composites. As a colleague of mine at Delaware, Prof. R. Byron Pipes has greatly enriched my perspective on the subject matter. The scholarship and guidance of Prof. Anthony Kelly have always been a source of inspiration to me. Prof. Jerzy L. Nowinski encouraged me throughout the course of this endeavor
1 Introduction 1.1 Evolution of engineering materials Compared to the evolution of metals,polymers and ceramics, the advancement of fiber composite materials is relatively recent. Ashby (1987)presented a perspective on advanced materials and described the evolution of materials for mechanical and civil engineering.The relative importance of four classes of materials (metal,polymer,ceramic and composite)is shown in Fig.1.1 as a function of time.Before 2000 BC,metals played almost no role as engineering materials;engineering (housing,boats,weapons,uten- sils)was dominated by polymers (wood,straw,skins),composites (like straw bricks)and ceramics (stone,flint,pottery and,later, glass).Around 1500 BC,the consumption of bronze might reflect the dominance in world power and,still later,iron.Steel gained its prominence around 1850,and metals have dominated engineering design ever since.However,in the past two decades,other classes of materials,including high strength polymers,ceramics,and structural composites,have been gaining increasing technological importance.The growth rate of carbon-fiber composites is at about 30%per year-the sort of growth rate enjoyed by steel at the peak of the Industrial Revolution.According to Ashby the new materials offer new and exciting possibilities for the designer and the potential for new products. 1.2 Fiber composite materials Fiber composites are hybrid materials of which the com- position and internal architecture are varied in a controlled manner in order to match their performance to the most demanding structural or non-structural roles.The fundamental characteristics of fiber composites have been summarized by Vinson and Chou (1975),Chou and Kelly (1976),Chou,Kelly and Okura (1985), Kelly (1985),and more recently by Chou,McCullough and Pipes (1986),from which the following is excerpted.* On the face of it a composite might seem a case of needless complexity.The makings of ideal structural materials would appear From 'Composites',Chou,MeCullough and Pipes.Copyright C (1986)by Scientific American,Inc.All rights reserved
Introduction 1.1 Evolution of engineering materials Compared to the evolution of metals, polymers and ceramics, the advancement of fiber composite materials is relatively recent. Ashby (1987) presented a perspective on advanced materials and described the evolution of materials for mechanical and civil engineering. The relative importance of four classes of materials (metal, polymer, ceramic and composite) is shown in Fig. 1.1 as a function of time. Before 2000 BC, metals played almost no role as engineering materials; engineering (housing, boats, weapons, utensils) was dominated by polymers (wood, straw, skins), composites (like straw bricks) and ceramics (stone, flint, pottery and, later, glass). Around 1500 BC, the consumption of bronze might reflect the dominance in world power and, still later, iron. Steel gained its prominence around 1850, and metals have dominated engineering design ever since. However, in the past two decades, other classes of materials, including high strength polymers, ceramics, and structural composites, have been gaining increasing technological importance. The growth rate of carbon-fiber composites is at about 30% per year - the sort of growth rate enjoyed by steel at the peak of the Industrial Revolution. According to Ashby the new materials offer new and exciting possibilities for the designer and the potential for new products. 1.2 Fiber composite materials Fiber composites are hybrid materials of which the composition and internal architecture are varied in a controlled manner in order to match their performance to the most demanding structural or non-structural roles. The fundamental characteristics of fiber composites have been summarized by Vinson and Chou (1975), Chou and Kelly (1976), Chou, Kelly and Okura (1985), Kelly (1985), and more recently by Chou, McCullough and Pipes (1986), from which the following is excerpted.* On the face of it a composite might seem a case of needless complexity. The makings of ideal structural materials would appear * From 'Composites', Chou, McCullough and Pipes. Copyright © (1986) by Scientific American, Inc. All rights reserved
Fig.1.1.The evolution of materials for mechanical and civil engineering.(After Ashby 1987.) 10000BC 5000BC 0 100015001800 1900 1940 1960 1980 1990 2000 2010 2020 Gold Copper.Bronze Metals Iron Metals Glassy metals Al-Li alloys Development slow: Cast iron Dual phase steels mostly quality Polymers Steels Microalloyed stccls control and New super-alloys processing Wood Skins Alloy stcels Fibers Glues Light alloys Polymers Rubber Composites Super-alloys Conducting polymers Straw bricks Paper Titanium High-temperature Zirconium Alloys polymers Stone etc. High-modulus Flint polymers Composites Pottery Bakelite Ceramic composites Glass Polyesters Nylon Metal matrix Cement PE Epoxies composites PMMA Acrylics Kevlar-FRP Ceramics Refractories PC PS PP CFRP Ceramics Portland GFRP cement Fused Pyro- Tough engineering silica Cermets ceramics ceramics (Al2O.SiaNa.PSZ etc.) 10000BC5000BC01000115001800 1900 1940 1960 1980 1990 2000 1201012020 Year
Fig. 1.1. The evolution of materials for mechanical and civil engineering. (After Ashby 1987.) 10 000BC Glassy metals Al—Li alloys Dual phase steels Microalloyed steels New super-alloys Development slow mostly quality control and processing Wood Skins Fibers Light alloys Super-alloys Conducting polymers High-temperature polymers High-modulus Composites | Straw bricks Paper Titanium "j Zirconium > Alloys etc. J Ceramic composites Polyesters ./'Metal matrix Epoxies ^ r composites PMMA Acrylics ^Kevlar-FR P PC PS PP ^XCFR P Jf I Ceramics FRP_ pyro_ Tough engineering Cermets£)£(> ceramics (A12O3, Si3N4, PSZ etc. I I 10 000BC 5000 BC 100011500 1800 2020 2010 i 2020 Year