Abstract
Hot drape formation of out-of-autoclave (OOA) prepregs is a promising manufacturing process for the aerospace and automotive industries, as it offers a reduction in overall processing time and cost. This study aims to examine the formability of out-of-autoclave 8-harness satin woven carbon/epoxy prepregs into complex shapes using a custom-made diaphragm forming set-up. In the diaphragm forming process, a composite laminate is placed between two deformable sheets, known as diaphragms. The diaphragms are then clamped, heated with the laminate to the processing temperature, and formed to the mold by applying vacuum pressure beneath the lower diaphragm. The current study carried out a double-diaphragm forming procedure at different forming rates and temperatures in order to examine the contribution of these parameters to part quality. A one-step procedure was used for both forming and curing processes using the same set-up. Observed defects, such as wrinkles, were compared against various processing parameters. In addition, the in-plane shear resistance of 8-harness satin woven carbon/epoxy prepreg prior to the forming process was investigated using a bias-extension test. The study shows that higher processing temperatures help to decrease the degree of wrinkling that occurs in the forming part. Meanwhile, the outer diameter of double-curved parts was found to conform more closely to the original shape when forming proceeded at a slower rate.