Non-linear viscoplastic behavior of fiber reinforced polymer composites

The non-linear behavior of polymeric fiber composite materials was studied theoretically in terms of a model developed for elastic–plastic materials, and generally valid for elastic–plastic response. This theory is focused on the current material state and connects material anisotropic response with identifiable directions in the present material state. Moreover, a functional form of the rate of plastic deformation is presented, that is further developed to predict the strain rate effect, that is also exhibited by the materials. The proposed theoretical model was adequate to agree well with the experimental stress–strain results in simple tension of off-axis fiber composites, that were experimentally tested in another work.