Contents 3.4.8.1 Free-edge delamination 160 3.4.8.2 General delamination problems 165 3.4.9 Enhancement of composite strength through fiber prestressing 166 4 Short-fiber composites 169 4.1 Introduction 169 4.2 Load transfer 169 4.2.1 A single short fiber 170 4.2.2 Fiber-fiber interactions 171 4.3 Elastic properties 176 4.3.1 Unidirectionally aligned short-fiber composites 177 4.3.1.1 Shear-lag analysis 177 4.3.1.2 Self-consistent method 177 4.3.1.3 Bound approach 178 4.3.1.4 Halpin-Tsai equation 181 4.3.2 Partially aligned short-fiber composites 182 4.3.3 Random short-fiber composites 187 4.4 Physical properties 194 4.4.1 Thermal conductivity 194 4.4.2 Thermoelastic constants 198 4.5 Viscoelastic properties 200 4.6 Strength 201 4.6.1 Unidirectionally aligned short-fiber composites 202 4.6.1.1 Fiber length considerations 203 4.6.1.2 Probabilistic strength theory 205 4.6.2 Partially oriented short-fiber composites 216 4.6.3 Random short-fiber composites 224 4.7 Fracture behavior 227 5 Hybrid composites 231 5.1 Introduction 231 5.2 Stress concentrations 233 5.2.1 Static case 233 5.2.2 Dynamic case 243 5.3 Tensile stress-strain behavior 247 5.3.1 Elastic behavior 249 5.3.2 First cracking strain 251 5.3.3 Differential Poisson's effect 254 5.3.4 Differential thermal expansion 256Contents X1 3.4.8.1 Free-edge delamination 160 3.4.8.2 General delamination problems 165 3.4.9 Enhancement of composite strength through fiber prestressing 166 4 Short-fiber composites 169 4.1 Introduction 169 4.2 Load transfer 169 4.2.1 A single short fiber 170 4.2.2 Fiber-fiber interactions 171 4.3 Elastic properties 176 4.3.1 Unidirectionally aligned short-fiber composites 177 4.3.1.1 Shear-lag analysis 177 4.3.1.2 Self-consistent method 177 4.3.1.3 Bound approach 178 4.3.1.4 Halpin-Tsai equation 181 4.3.2 Partially aligned short-fiber composites 182 4.3.3 Random short-fiber composites 187 4.4 Physical properties 194 4.4.1 Thermal conductivity 194 4.4.2 Thermoelastic constants 198 4.5 Viscoelastic properties 200 4.6 Strength 201 4.6.1 Unidirectionally aligned short-fiber composites 202 4.6.1.1 Fiber length considerations 203 4.6.1.2 Probabilistic strength theory 205 4.6.2 Partially oriented short-fiber composites 216 4.6.3 Random short-fiber composites 224 4.7 Fracture behavior 227 5 Hybrid composites 231 5.1 Introduction 231 5.2 Stress concentrations 233 5.2.1 Static case 233 5.2.2 Dynamic case 243 5.3 Tensile stress-strain behavior 247 5.3.1 Elastic behavior 249 5.3.2 First cracking strain 251 5.3.3 Differential Poisson's effect 254 5.3.4 Differential thermal expansion 256