Compression moulding of glass and polypropylene composites for optimised macro- and micro- mechanical properties Part 3 : sandwich structures of GMTS and commingled fabrics

The co-moulding of random-reinforced GMTs with commingled E-glass and polypropylene fabrics was investigated in a series of experiments which were designed statistically. Materials were heated in an infra-red oven prior to non-isothermal compression moulding. Maximum preheat times and temperatures were determined by gel permeation chromatography to monitor the onset of degradation of the polymer matrix. Laminate properties were mapped according to the processing parameters and optimum conditions for consolidation were identified. The process parameters were ranked in order of importance for maximum flexural modulus and time at pressure proved the most significant factor. Microscopy was used to investigate the impregnation mechanisms and the subsequent removal of voidage.