Analyzing Loads and Strains in Polymer-Matrix Composites

Strain Rate Dependent Analysis of Polymer Matrix Composites (STRANALPMC) is a computer program for analyzing strain-rate-dependent, nonlinear deformation and failure responses of composite materials in which the matrices are ductile polymers. Modified versions of the Ramaswamy-Stouffer constitutive equations of viscoplasticity, originally developed for metals, are used to represent deformation of a polymeric matrix. The equations are applied in a micromechanical approach, in which each unit cell is divided into several slices. Appropriate uniform stress and uniform strain assumptions, along with the constitutive equations for the fiber and matrix, are used to compute the response of the slice. Laminate theory is then applied to obtain the effective response of a ply, and is applied again to obtain the effective response of a multilayered composite laminate. To predict the ultimate strength of each composite ply, the Hashin failure criteria are implemented within the micromechanics. The constitutive equations are integrated in time by a Runge-Kutta technique. The inputs to STRANAL-PMC are the geometry of the composite laminate, the properties of the fiber and matrix materials, and the applied stress or strain versus time. The outputs of STRANAL-PMC are the stress and strain at the slice, ply, and laminate levels at each time step.