The Effects of Process Parameters on the Porosity of a VBO Prepreg/Fiber-Interleaved Layup Composite

Abstract

This research aimed to explore the porosity characteristics of a “hybrid” layup composite; this involved combining a fully impregnated prepreg and a dry fiber fabric via the the vacuum-bag-only (VBO) manufacturing process to create unidirectional carbon-fiber laminates sized at 15 × 15 cm². This investigation delved into several VBO process parameters encompassing the debulking technique, curing cycle, laminate saturation index, and thickness. The primary goal was to comprehend how these factors impacted the porosity levels within the laminate. Elevating the dwelling temperature during the curing cycle, employing a saturation index beyond 1.57, and utilizing thicker laminates emerged as strategies for decreasing the void content in the laminate. By implementing the optimal parameters identified through this research, we produced composite laminates that exhibited a substantial reduction in porosity. Furthermore, the study extended to modifying the two-stage curing cycle into a multi-stage cure cycle. This modification provided evidence that the incorporation of more dwell stages contributed to a further reduction in porosity. This study also featured a comparative analysis involving two types of laminates: one with prepreg fibers oriented at 0° and dry fibers oriented at 90° and another laminate with a sole 0° layup using a combination of prepreg and dry fibers. The findings suggest that the cross-layup allowed the prepreg fibers to conform more effectively to the protruding weft, thus eliminating voids induced by the weft. In conclusion, this research underscores the potential for a significant reduction in porosity within hybrid layup composites manufactured using the VBO process.