Off-Axis Tensile Properties of CFRP Laminates and Non-Linear Lamination Theory Based on Micromechanics Approach.

Abstract

This paper deals with the deformation and damage of CFRP cross-ply laminates under off-axis tension and develops a non-linear lamination theory. Off-axis tensile tests were carried out on five kinds of CFRP cross-ply laminates which were different in stacking lay-up. On the laminates under off-axis tension, the stress-strain response shows the non-linear deformation, while the ply-cracking damage is not remarkable except for the specimen with large fracture strain. Therefore, It is concluded that the non-linear deformation of the laminates under off-axis tension is mainly attributed to the non-linear deformation of the matrix resin. In order to describe the deformation of the laminates, a non-linear lamination theory is developed. An incremental constitutive relation of the unidirectional composite containing elastic long fibers in the elastic-plastic matrix is derived based on Eshelby's equivalent inclusion method and Mori-Tanaka mean field concept. Then, this constitutive relation is introduced Into the classical lamination theory. Numerical results by the present theory for off-axis tension of the CFRP unidirectional and cross-ply laminates well described the experimental stress-strain relations.