Effect of random vibration-assisted vacuum processing on void development and interfacial properties in composites

Voids and delamination are viewed as significant defects in the manufacturing process of carbon fiber-reinforced plastics structures and have been demonstrated to reduce the final performance of composites. Vibration is increasingly applied in new processing technologies for reducing void content and improving performance under low cure pressures. Therefore, this study investigates the effect of random vibration on the formation of voids during the curing process and the final interfacial properties of composite laminates. A 10 g random vibration was applied in the curing cycle, and a no-vibration cure cycle was designed as the experimental control group. The cure cycles were interrupted at pre-defined stages for each process to enable the in situ behavior of void content and growth of voids to be studied. Then the short-beam three-point bending test was employed to determine the interlaminar shear strength of composite samples. And the interlaminar cracks and fracture surfaces of tested specimens were captured by scanning electron microscopy. Besides, the interfacial shear strength of composite samples was measured by single-fiber push-in test. Compared with static group, the major benefits of the current research are that the growth of voids was impeded and void content was decreased obviously at each stage in composite samples produced by random vibration-assisted vacuum processing. In addition, the final interfacial properties were improved at the macro and micro levels due to adequate adhesion of the fiber–matrix interface when random vibration was introduced into the curing cycle.