Nonlinear Deformation of Laminated Composites

A method is presented for the nonlinear analysis of an element of a laminated composite using the Ramberg-Osgood stress-strain relation and considering transverse shear, degradation of elastic moduli due to fracture, and deformation theory of plasticity generalized for anisotropic inelastic material. An efficient solution is obtained employing the Newton-Raphson method for proportional or nearly proportional loading in incremental steps. At the end of each step failure criteria are applied to each layer as well as to the laminate to study failure due to yielding, fracture, delamination, and degradation of laminate stiffness. The method gives a better comparison with experimental results than previous inelastic analysis. Because of its generality, the method can be used as an effective tool for the selection of allowable stresses in the design of laminated composites.