The effect of fiber‐matrix adhesion on the fatigue fracture of glass‐fiber‐reinforced poly(vinyl chloride)

Abstract Fatigue crack propagation (FCP) of injection‐molded glass‐fiber‐reinforced poly(vinyl chloride) was examined as a function of fiber‐matrix adhesion (coupling) and fiber content at different load levels. Considering the entire FCP history, from crack initiation to critical propagation, it is shown that fatigue lifetime and fracture toughness of coupled composites increase with fiber weight fraction. Uncoupled material exhibits the highest fracture toughness at 10 wt% fiber, yet its fatigue life is considerably shorter. Damage analysis indicates that fiber debonding, pullout, and particularly fiber fracture seem to contribute to the higher fatigue lifetime noted in coupled composites. The Crack Layer Theory is employed to describe the observed FCP behavior. The effective enthalpy of damage parameterizes the resistance of the composite to FCP in terms of the observed mechanisms.