Effects of processing parameters for vacuum-bag-only method on void content and mechanical properties of laminated composites

Process parameters for vacuum-bag-only (VBO) method are of critical importance to control manufacturing-induced void content and mechanical properties of laminated composites. Currently, no comparative studies are readily available on various VBO processing parameters namely bagging techniques, cure cycles, and laminate thicknesses on induced defects and mechanical properties. Hence, this study investigates the effects of these parameters on manufacturing-induced void content and mechanical properties of composite laminates. Laminate samples were manufactured using L-27 Taguchi orthogonal array experimental plan. Void contents, tensile and flexural properties of these samples were evaluated. Double VBO technique and direct (modified) cure cycle were found to be the most promising parameters in achieving the lowest void content among choices of bagging techniques and cure cycles, respectively. However, improved mechanical properties were achieved using a single VBO technique due to the higher fiber reinforcement volume fraction. In comparison to a typical cure cycle, the modified cure cycles were able to reduce surface porosity and through-thickness void by 48.33% and 23.7%, respectively, whereas the tensile and flexural properties were increased by 2% to 3% and 17% to 20%, respectively. In addition, no significant interaction between parameters was observed.