Fatigue performance of long-fiber-reinforced polymers (FRPs) in relation with matrix properties

Better mechanical properties and fatigue performance of engineering materials are always desired in structural applications. In this study, in-plane random glass fiber which is a relatively new reinforcement in fiber-reinforced polymers (FRPs) was embedded in polymers (i.e. polyester and polyurethane). Mechanical properties of the polymers and FRPs were determined from static tests. Zero-tension fatigue loading of FRPs was conducted in order to study damage development, modulus degradation, and energy dissipation rate.; It was concluded that polyurethane-based FRP showed better fatigue resistance than polyester-based FRP at the applied load of 50% of their respective ultimate tensile strength (UTS), as indicated by longer fatigue lifetime, milder modulus degradation, and higher energy dissipation rate. Modulus degradation and energy dissipation rate were found to be correlated to damage development. The resistance to crack propagation in the polyurethane-based FRP was found to be related to the higher fracture toughness of the matrix.