Modelling of the thermokinetic behaviour and the phases transitions of a carbon/polymeric composite submitted to high heating rate ramps

Our on-going work focuses on curing time reduction owing to the Roctool Cage System® on aeronautical prepregs. Our very first aim is thus to define the limits of this process in order to get the shortest cure cycles (objective function) while respecting some constrained functions such as: no degradation of the polymeric matrix and final degree of cure α and Tg at least equal to those obtained on the autoclave-cured material according to the cure cycle recommended by the prepreg manufacturer. The prepreg investigated here is the Hexply M21/35%/268/T700GC carbon/polymeric matrix produced by Hexcel Composites France. The presence of thermoplastics enhances the risk of matrix degradation during curing. Effectively, in these kinds of polymers blends (when thermoplastic content > 10 wt %) phase separation may occur and modify the reaction rates. Beside the determination of the prepreg cure kinetics (studied by DSC), a Time Temperature Transformation diagram was settled. Consequently, the M21 matrix degradation was studied from room temperature up to 600°C by TGA for heating rates ranging from 1 up to 100°C/min.