Use of a cohesive-zone model to analyze the fracture of a fiber-reinforced polymer-matrix composite

A cohesive-zone model for a fiber-reinforced polymer-matrix composite is presented. A two-parameter model with a characteristic toughness and a characteristic strength can be used to predict the fracture of notched or cracked specimens. The two parameters can be determined by comparing numerical predictions to experimental observations of a fracture test. It is shown that the engineering behavior, in terms of strength, deformation and energy dissipation is well-described by such a two-parameter model, but when the characteristic dimensions of the composite structure (e.g., the initial crack length or ligament length) are very small, extra details about the cohesive law such as the matrix-cracking strength may be required. Finally, it is shown that a cohesive-zone model provides excellent predictions of transitions between stable and catastrophic crack growth in the composite, and, hence, permits an understanding of the energy dissipation during fracture that occurs in these different regimes.