Effects of cure cycles on void content and mechanical properties of composite laminates

Various curing cycles were designed to evaluate the effects of different pressure induced voids on some mechanical properties of carbon/epoxy laminates and optimum cure pressure time. A series of [0/90]3s laminates with varying void contents were fabricated and a characterization of void distribution, size, and shape within the laminates was obtained using ultrasonic c-scan and optical metallography techniques. Short beam shear, three-point flexure and tensile testing were used for mechanical evaluation and the results correlated to void volume fraction and ultrasonic absorption coefficient. The experimental results have shown that there exists an optimum time for applying pressure. The proposed grading evaluation method of ultrasonic inspection is helpful for the nondestructive examination of composites. Also, changes in mechanical performance due to porosity are consistent with previously published studies.