A Study on Mechanical Behavior of Composite Materials Using Nonlinear Micromechanics of Failure

Abstract

A new methodology, called micromechanics of failure (MMF), was developed in order to provide a more profound view into the microscopic failure mechanism of composite laminate, and subsequently better the failure prediction of composites under multi-axial loadings. Based on micromechanical unit cell models which characterize microstructure of composite, current MMF consists of independent constituent failure criteria and a progressive damage model for the matrix. Once the micro stress state in matrix satisfies the matrix failure criterion, initial failure occurs, and matrix stiffness commences decreasing in a pattern specified in the progressive damage model until final failure is achieved. Consequently, the nonlinear ply behavior in matrix-dominant directions is caught. Several examples of nonlinear ply behavior predicted by MMF are shown. Thermal stresses due to the difference between room temperature and stress-free temperature were also considered. Results of prediction are presented together with explanation.