Fatigue damage of cohesive interfaces in fiber-reinforced polymer composite laminates

The weak interfaces in fiber-reinforced polymer (FRP) composite laminates often dictates the reliability of the composite structures. In this respect, a new cyclic cohesive zone model (CCZM) is introduced for accurate quantitative description of the interlaminar fatigue failure process. The model incorporates the interlaminar damage through the measured fatigue degradation of the strength, stiffness, and critical energy release rate properties. A combined experimental-finite element (FE) approach is employed to establish the residual interlaminar properties. The new CCZM is examined for the case study on the end-notched flexure (ENF) beam specimen of unidirectional carbon fiber-reinforced polymer (CFRP) composite laminate. The calculated applied resultant shear stress at the critical interface material point, adjacent to the pre-existing crack front, fluctuates at (tau(max) = 30 MPa, R = 0.1). The interlaminar shear-induced damage shows a sigmoidal form of the damage evolution curve. The pre-existing interface crack propagation begins at 301750 cycles, while maintaining an almost straight advancing crack front.