A Simple Flow Rule for Characterizing Nonlinear Behavior of Fiber Composites

A one-parameter flow rule for orthotropic plasticity was developed to describe nonlinear behavior of fiber composites. Since most fiber composites exhibit in significant plasticity in the longitudinal direction, a plastic potential containing a single parameter was found adequate. Effective stress and plastic strain increment were intro duced to yield a universal nonlinear stress-strain relationship for the orthotropic com posite. This plasticity model was evaluated using experimental results of a boron/ aluminum and a graphite/epoxy composite.