DAMAGED ELASTOPLASTIC BEHAVIOR OF [+PHI,-PHI](N) FIBER-REINFORCED COMPOSITE LAMINATES IN BIAXIAL LOADING

This paper proposes a model describing the mechanical behaviour of [+phi, -phi](n) composite laminates. For short-term tests, the behaviour of laminates is damaged elasto-plastic. The damage is described by using micro-macro modelling which permits only one parameter if the flaws have the same density through the thickness of the material. The damage rate is obtained by the definition of a criterion and an associated phenomenological flow rule. The same method supplies the plastic strain rate, which is based on a criterion which provides no plastic strain in the fibre direction. The model is established for a [+55, -55](n) lay-lip. The tests are performed on filament-wound laminate tubes under biaxial tensile and internal pressure loading.