Vacuum bag moulding of large thermoplastic parts in commingled glass/PET copolymer

This paper describes the development of a thermoplastic composite system for structural application in the chassis of an electrically propelled bus. The work involved the characterisation and modelling of a vacuum bag moulding process using a woven commingled thermoplastic composite precursor. The matrix materials were PET and a PET copolymer. The process employs an ambient pressure oven, with tooling that can be made from composite, metal or ceramic. The process results in good quality laminates, with a void content generally lower than 1%. The temperature profile through the part and the consolidation behaviour were characterised and modelled. It was found that the thermal profile could be modelled with adequate accuracy using ‘single point’ values of thermal properties. Experimental measurements showed, for the first time, that consolidation occurs in two stages: a low temperature solid state debulking near to Tg, followed by full melt impregnation at a higher temperature (above Tm in the case of the homopolymer). Both stages in the consolidation process were modelled separately using a simplified version of the Kamal equation.

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