The Nonlinear Behavior of Unidirectional and Laminated Composites— A Micromechanical Approach

A micromechanics theory for the prediction of the nonlinear behavior of unidirectional fiber-reinforced materials and composite laminates is presented. The method relies on the properties of fibers and matrix, and involves two parameters which describe the nonlinear response of the unreinforced matrix. These two parameters can be backed-out from the nonlinear axial shear response of the unidirectional lamina. The pre dicted behavior of boron/epoxy, glass/epoxy and graphite/polyimide composites is com pared with available measured data, and good agreement is obtained in most cases.