Plastic Flow Rule of Laminated Composites

A plastic flow rule for laminated media is derived. It is based on a three-dimensional lamination theory which has been used previously to provide an effective elastic stress-strain relation and an anisotropic yield condition. For layers that are isotropic and follow a piece-wise linear flow rule, an explicit anisotropic plastic stress-strain relation for the equivalent composite is obtained. The general form of this flow rule may also be applied to other homogeneous but anisotropic materials. It is concluded that anisotropic flow rules should be governed by tensor quantities, the symmetry of flow may be different from that of yielding, and plastic flow may occur under hydrostatic loading.