Vacuum consolidation of commingled thermoplastic matrix composites for marine applications

An experimental and modelling study was conducted on the vacuum consolidation of commingled glass/thermoplastic composites as part of a larger project on manufacturing large monolithic structures from these precursors, such as those that could be used for marine structures. Two matrices were employed: semi-crystalline PET and an amorphous PET copolymer. Samples of commingled fabric were processed into consolidated composites by means of both a convective oven, as would be used in a real marine production environment, and a small scale experimental characterisation rig, designed to measure consolidation accurately. The samples were then cooled to room temperature. In this paper, the thermal and consolidation characterisation of these fabrics is reported. Thermally induced consolidation was observed to occur in two stages: a low temperature solid state de-bulking near to T-g, followed by full melt impregnation at a higher temperature. Both stages were modelled separately using an empirical model based on the Kamal equation. The measured consolidation vs. time profiles suggested a rapid impregnation and wetting of the fibres, occurring near to the melting point of the semi-crystalline polymer. The PET melting endotherm and crystallisation exotherm had little effect on the observed thermal profiles, suggesting that these effects could possibly be neglected when modelling the process.