LOCAL AND INTERFACIAL DAMAGE ANALYSIS OF METAL-MATRIX COMPOSITES

Damage and plastic deformation is incorporated in the proposed model that is used for the analysis of fiber-reinforced metal matrix composite materials. The proposed micromechanical damage composite model used here is such that separate local constitutive damage relations are used for each of the matrix and the fiber. This is coupled with the interfacial damage between the matrix and the fiber exclusively. The damage relations are linked to the overall response through a certain homogenization procedure. Two local damage tensors are used M(m) and M(f) where M(m) accounts for the damage in the ductile matrix such as nucleation and growth of voids, while the tenser M(f) reflects the damage in the fibers such as fiber fracture. An additional tenser Md is incorporated in the overall formulation that represents interfacial damage between the matrix and the fiber. An overall damage tenser, M, is introduced that accounts for all these separate damage tensors M(m), M(f), and M(d). For the undamaged matrix material, a von Mises type yield criterion with an associated flow rule, and a Ziegler-Prager kinematic hardening rule are used. However, the resulting overall yield function for the damaged composite is of the anisotropic type. The overall kinematic hardening rule for the damaged composite system is a combination of the generalized Ziegler-Prager rule and a Phillips-type rule. The elasto-plastic stiffness tenser is derived for the damaged composite. Numerical solutions are obtained using the proposed theory for two types of laminate layups (0/90)(s) and (+/-45)(s) each consisting of four plies and compared with experimental results. A very good correlation is obtained between the experimental and numerical results.