Modeling damage in polymeric composites

We postulate that dominant damage modes in a fiber-reinforced laminated composite are fiber breakage, matrix cracking, fiber/matrix debonding, and delamination/sliding. The first three damage modes are represented by internal variables with their development governed by constitutive relations. The delamination/sliding failure mode is presumed to initiate at a point on an interface between two adjoining layers when the transverse shear and the transverse normal stresses there are on a failure surface defined in the stress space. Equations expressing the balance of mass, the balance of linear momentum, the balance of moment of momentum, material response, and those giving the development of damage are simultaneously solved numerically under prescribed initial and boundary conditions to find an approximate solution of a transient 3-dimensional initial-boundary-value (IBV) problem. Values of material parameters for the AS4/PEEK composite are determined from experimental data available in the literature. The developed mathematical model has been validated by comparing computed results, for several IBV problems different from the ones used to find values of material parameters, with the corresponding experimental results available in the literature.