The influence of preliminary cyclic deformation on the strength properties and the fracture kinetics of a unidirectional carbon fiber reinforced polymer composite material is studied. The effect of the preliminary cyclic loading amplitude on damage (investigated by X-ray computed tomography), acoustic emission parameters, and the characteristics of local deformed state (estimated by digital image correlation) is analyzed. Preliminary cyclic loading is found to cause an increase in the ultimate tensile strength and the fracture energy. A strain field investigation shows that the fracture of the specimen is accompanied by the formation of multiple defective regions characterized by a high local strain. Preliminary cyclic loading is found to bring about the nucleation of defects in the specimen volume, and they cause premature matrix cracking and the development of delamination at the fiber–matrix interface. This behavior is confirmed by the results of frequency–energy analysis of AE signals at various stages of fracture.
Tyutin et al. (Thu,) studied this question.