Experimental Study on Rotating Bending Fatigue Behavior of Carbon Fiber Reinforced with Epoxy Composites Using Statistical Analysis

In this study, rotating bending fatigue tests have been conducted for carbon fiber-reinforced epoxy composites. Hollow cylindrical specimens were prepared for two different lay-up sequences, i.e., [+/- 45 degrees](2) and [+/- 45 degrees/(90 degrees)(2)] using filament winding process. These specimens were tested at constant stress levels with zero mean stress using an in-house built rotating bending fatigue testing machine. Several failure modes including matrix cracking, fiber pull-out, and longitudinal splitting of fibers from the matrix and fiber failure have been ascertained using a scanning electron microscope. The probability distribution of fatigue life results of the test specimens is statistically analyzed using the two-parameter Weibull distribution function. Higher shape parameters are witnessed for both the stacking sequences at lower stress levels, indicating less dispersion in the fatigue life during high cycle fatigue. S-N diagrams are drawn for the different probability of failures (P-f = 0.10, P-f = 0.37, P-f = 0.50, and P-f = 0.99) for the benefit of machine designers to identify the first failure time.