The Analysis of Fatigue Damage to Glass-Fiber Reinforced Composites

We perform a complex investigation of the mechanism of fatigue fracture of epoxy–fiberglass compositions (with 80 wt.% of fiberglass) by using mechanical, fractographic, and acoustic-emission methods. Flat specimens are cyclically loaded by displacement-controlled console bending. As a criterion of loss of the fatigue strength of a specimen, we use an increase in its flexibility by 40%. The lateral surfaces and cross sections of the specimens are analyzed after the attainment of this criterion. Periodically, after different numbers of lading cycles, we record acoustic-emission signals. As the basic parameter, we use the so-called MARSE energy. Different energy levels of the signals are explained by the action of different fracture mechanisms (failures of the matrix and fibers and exfoliations along the fiber–matrix boundary). This enables us to establish the periodicity and intensity of each type of signals depending on the load.