ALVES, H. ; KOTIK, H. ; CAMERINI, CESAR G. .
Resumo: The vast majority of fiber-reinforced polymer (FRP) composites are known to exhibit stiffness degradation during fatigue life. Based on this phenomenon, predictive models have been developed to evaluate the residual life of FRP components and structures subjected to cyclic loading. However, some researchers reported an increase in residual stiffness of laminated composites under different experimental conditions (fiber orientations, loading types, stress ratios, etc.), representing a gap in the FRPs fatigue theory. To understand this phenomenon, unidirectional laminates of carbon and glass fiber-reinforced polymer (CFRP and GFRP) were tested by tension- tension fatigue up to 10⁴ cycles. The experimental procedure followed the ASTM D3479-19 standard and employed a stress ratio (R) of 0.1 and a frequency of 1 Hz. Residual stiffness was monitored using extensometers in quasi- static and cyclic conditions. The GFRP specimens were also characterized by computed tomography (CT) to detect the fiber realignment. The mechanical testing showed a decrease in residual stiffness, confirming the degradation theory. CT images did not reveal significant changes in fiber alignment.
