ABSTRACT
Natural bers such as ax, hemp, kenaf, jute, sisal, ramie, and coir are often considered as reinforcing polymers for enhanced performance. Indeed, the stiffness of these bers in the axial direction is on par with that of glass bers (for instance, 50-100 GPa stiffness is reported for ax bers). There are well-known advantages of
9.1 Introduction .................................................................................................. 221 9.2 Multiscale Modeling of Natural Fiber Stiffness ........................................... 223
9.2.1 Hierarchical Structure of Fibers ....................................................... 223 9.2.2 N-phase Concentric Cylinder Assembly ...........................................224 9.2.3 Examples for Elastic Constants of a Layer in the Fiber Wall ...........226 9.2.4 Elastic Properties of the Fiber Wall ..................................................228 9.2.5 Elastic Constants of the Fiber ........................................................... 231
9.3 Stiffness of Composites ................................................................................ 231 9.3.1 Rule of Mixtures ............................................................................... 231 9.3.2 Shear-Lag Parameter ........................................................................ 232 9.3.3 Composites with In-Plane Fiber Orientation Distribution ................ 233 9.3.4 Random Composites .........................................................................234 9.3.5 Numerical Methods .......................................................................... 235
9.4 Strength of Composites ................................................................................. 237 9.4.1 Rule of Mixtures ............................................................................... 237 9.4.2 Laminate Analogy ............................................................................ 237
9.5 Moisture Expansion of Natural Fiber Composites ....................................... 238 9.6 Inelastic Behavior of Natural Fibers and Their Composites ........................240
