Theoretical description of large deformations in criss-cross composites (with application to Tensylon®)

A theoretical model of an anisotropic material, Tensylon (R), under large strains is proposed. This model is capable to describe the material's response in in-plane tension at different angles to the fibrils. At 0 degrees and at 90 degrees, i.e., along the fibrils in either "criss" or "cross" plies, it quantitatively predicts the experimentally observed elastic behaviour until failure. At 45 degrees to the fibrils, it quantitatively describes the experimental data in the elastic and plastic domains. The description remains accurate up to strains of 35%, that corresponds to 30 divided by 40% of deformation gradient components. The infinitesimal strains model would give at least 25% of error under such circumstances.