Understanding the mechanical behavior of fiber/matrix interfaces during push-in tests by means of finite element simulations and a cohesive zone model

The present work represents a progress towards the understanding of the mechanical behavior of the fiber/matrix interface during push-in tests of fiber-reinforced polymer-matrix composites. Finite element simulations incorporating a cohesive zone model are used for this purpose. Different values of interface strength, interface fracture toughness, fiber diameter and friction coefficient are considered to study how they affect the load–displacement curves. A critical value of the displacement exists, being independent of the fiber diameter for given values of interface strength and fracture toughness, marking the separation between two regimes: (i) a cohesive-dominated zone interaction and (ii) a frictional contact between debonded fiber and matrix. Maps showing the different regimes are constructed, proving their helpfulness to tune the mechanical properties of the interface in order to favor a certain mechanical response. Finally, we study the debonding velocity and how this is affected by the mechanical properties of the interface providing an empirical relation.