Novel epoxy powder for manufacturing thick-section composite parts under vacuum-bag-only conditions. Part I: Through-thickness process modelling

Thick-section composite parts are difficult to manufacture using thermosetting resins due to their exothermic curing reaction. If processing is not carefully controlled, the build-up of heat can lead to warpage or material degradation. This risk can be reduced or removed with the use of a low-exotherm resin system. Material and process models are presented which describe vacuum-bag-only processing of thick-section composites using a novel, low-exotherm epoxy powder. One-dimensional resin flow and heat transfer models are presented which govern the fabric impregnation and temperature evolution, respectively. A semi-empirical equation is presented which describes the sintering of the epoxy powder. The models are coupled via laminate thickness change, which is determined for a simplified ply microstructure. The resulting system of equations are discretised and solved numerically using a finite difference code. A case study is performed on a 100-ply laminate, and the advantages and disadvantages of using epoxy powders are discussed.