Micromechanics of short-fiber composites

Short fibers are currently being introduced into sheet-molding compounds (SMC), metal matrix composites (MMC), brittle matrix composites (BMC), and a variety of other materials to enhance the mechanical properties exhibited by these composites. The scientific community endeavors to represent theoretically the complex interaction between the short fibers and the surrounding matrix, both globally and locally, in an attempt to infer material behavior. The model presented here predicts the point-wise stresses in the fiber and the matrix including the stress state at fiber ends. This solution admits the possibility of load transfer between the fiber ends and matrix. The present analysis is also applicable to composites containing broken fibres. The model is developed from the elasticity solution of the concentric cylinder assemblage, coupled with an approximate solution to the classical shear-lag problem. The modeled composite can involve varying fiber orientations, different fiber lengths, and different fiber types. The stiffness tensor of the composite is calculated by globally averaging the approximate stresses in the representative fibers and matrix embedded in the composite. Validation consists in comparing predicted elastic properties with experimental results as well as other theoretical models available in the literature.