Critical strain energy release rate of woven carbon/epoxy composites subjected to thermal cyclic loading

Abstract In the current study, experimental and numerical approaches were adopted to investigate the effect of thermal cyclic load on the delaminated beam behavior of woven carbon/epoxy laminated composites. For this purpose, composite specimens were prepared according to ASTM standard and subjected to 175 thermal cycles in the range of −30 to 60°C before conducting the mode I and mode II interlaminar fracture tests. Experimental results revealed that thermal cycles lead to a drop in maximum loading capacity of the delaminated beam as well as the interlaminar fracture toughness of the woven carbon/epoxy composites. The beam fracture toughness at initiation and propagation decreased by 8% and 12% under mode I loading and by 13.84% and 15.64% under mode II loading, respectively. In the numerical analysis, the cohesive zone model was utilized in order to predict the global response of the delaminated beams. The micro and scanning electron microscope images of fracture surfaces provide efficient insights into the identification of the main mechanisms contributing to decreasing fracture toughness under cyclic thermal load. These images show that specimens subjected to cyclic thermal load exhibited smoother surfaces, which could be due to weaker bonding between matrix and fibers after cyclic thermal loading.