Cure kinetics, glass transition and chemoviscosity models for an aerospace-grade disulphide-based benzoxazine vitrimer

Abstract

This study reports the matrix material models for the manufacturing of reinforced fibre composites using a disulphide-enabled aerospace-grade benzoxazine vitrimer. Cure kinetics and chemoviscosity models, crucial for fibrous composite manufacturing optimisation, were developed using calorimetric and rheometric data, respectively. An autocatalytic model with a logistic term accounting for diffusion represents accurately the resin cure kinetics, with 4 % average relative error in degree of cure prediction. The glass transition (Tg) evolution follows the DiBenedetto equation, with a curvature parameter (λ) of 1.84. A chemorheological model based on the kinetics of viscosity at a reference temperature and an inverse temperature exponential dependence—appropriate for low degrees of cure prevailing during the filling/consolidation step of fibrous composite manufacturing—simulates rheological behaviour with an average error of 8.3 %. The initial viscosity ranges from 144.7 mPa·s at 130°C to 1119 mPa·s at 100°C, with fast evolution which limits impregnation, meaning that composites processing using a resin film infusion or pre-impregnation route is applicable to this vitrimeric matrix.