Fatigue behavior of symmetric and asymmetric carbon and basalt fiber-reinforced polymer composites in transverse loading

This research aims to examine the influence of altering the relative arrangement of (0 degrees/90 degrees) and (+/- 45 degrees) angle plies with respect to the midplane of a laminate on the flexural and fatigue characteristics of fiber-reinforced composites composed of carbon and basalt fibers with an epoxy matrix. Three laminate configurations of carbon and basalt fiber-reinforced laminate were examined: These configuration included an eight-layer symmetric [(0 degrees/90 degrees)/(+/- 45 degrees)2/(0 degrees/90 degrees)]//[(0 degrees/90 degrees)/(+/- 45 degrees)2/(0 degrees/90 degrees)] and an eight layer asymmetric having [(0 degrees/90 degrees)/(+/- 45 degrees)2/(0 degrees/90 degrees)//(+/- 45 degrees)/(0 degrees/90 degrees)2/(+/- 45 degrees)], and (+/- 45 degrees)/(0 degrees/90 degrees)2/(+/- 45 degrees)//(0 degrees/90 degrees)/(+/- 45 degrees)2/(0 degrees/90) stacking sequence. Flexure and fatigue tests were conducted on FRP composites under monotonic and cyclic loading. Varied parameters were carefully chosen, including load range (90-50%), loading frequency (f = 1 Hz), stress ratio (R = 0.1), and different stacking sequences. The findings of this study unveiled noteworthy insights. (1) The flexural and fatigue properties of the C-SYM and B-SYM specimens surpassed those of their respective asymmetric specimens, indicating their superior performance in bending applications. (2) The flexural modulus of the fibers played a pivotal role in determining the failure mode observed in the composite coupons, underscoring the significance of fiber properties in composite behavior. (3) Fatigue failure in the composites was attributed to the progressive propagation of damage, highlighting the cumulative nature of structural deterioration under cyclic loading conditions.