Fabrication and quality analysis of angle composite part by vacuum-bag-only process with interleaved woven fiber/prepreg layup

This study used the vacuum-bag-only (VBO) process to fabricate angle composite parts with interleaved layup of prepreg and dry fibers. The quality of angle parts is investigated by statistical methods, which are divided into two parts: geometric characteristics and internal characteristics. The results indicated that the part fabricated by the convex mold presented higher dimension stability and uniformity as compared to that by the concave mold. According to the results, increasing the laminate thickness and decreasing the angle mold could effectively reduce the corner thickness deviation and angle deviation percentages. In addition, the lead caul plate could effectively improve the thickness change in the corner area in both the concave and convex molds, and both the lead and Si-rubber caul plates could significantly reduce the angle deviation. For the internal characteristics, to quantify the void content of the laminate, we propose a scoring mechanism to analyze angle part. The part fabricated by the convex mold has a higher score than that by the concave mold. In order to fully understand the thickness variation of the part at the corner region, a semi-empirical model was proposed to calculate the corner thickness deviation in different mold geometry and stacking thickness. In this study, the prediction errors of the semi-empirical model for the parts by the concave and convex molds are 17.6% and 16.1%, respectively. The results of this research can also be extended to other VBO processes with more complicated geometries and provide advice and guideline on mold design and process conditions.