Vacuum Consolidation of Commingled Thermoplastic Matrix Composites

Abstract

An experimental and modeling study is conducted on the vacuum consolidation of commingled glass/thermoplastic composites as part of a larger project on manufacturing large monolithic structures from these precursors. Two polyethylene terephthalate (PET) matrices are employed: semicrystalline PET and an amorphous PET copolymer. Samples of commingled fabric are processed into consolidated composites by means of both a convective oven, as will be used in practice, and a small-scale experimental characterization rig, designed to measure consolidation accurately. The samples are then cooled to room temperature. In this article, the thermal and consolidation characterization of these fabrics is reported. Thermally induced consolidation is observed to occur in two stages: a low temperature solid state de-bulking near to Tg, followed by full melt impregnation at a higher temperature. Both stages are modeled separately using an empirical model based on the Kamal equation. The measured consolidation versus time profiles suggest a rapid impregnation and wetting of the fibers, occurring near to the melting point of the semicrystalline polymer. The PET melting endotherm and crystallization exotherm have little effect on the observed thermal profiles, suggesting that these effects can possibly be neglected when modeling the process.