Thermoplastic hybrid-matrix composites prepared by a room-temperature vacuum infusion and in-situ polymerisation process

This work explores a novel route for the fabrication of hybrid-matrix composites based on a recently developed liquid thermoplastic acrylic resin. This resin was modified using a poly(phenylene ether) (PPE) oligomer with vinyl functionality. Glass fibre-reinforced laminates based on acrylic and PPE-modified acrylic matrices were produced by a room-temperature vacuum infusion and in-situ polymerisation process. Comparative assessments of their mechanical performance and mode-I interlaminar fracture behaviour revealed enhanced matrix ductility, transverse flexural properties and initiation fracture toughness. Crazing was identified as the dominant mechanism for improved resistance to crack initiation

Novel epoxy powder for manufacturing thick-section composite parts under vacuum-bag-only conditions. Part II: Experimental validation and process investigations

Validations of a one-dimensional process model are carried out by manufacturing thick-section glass-fibre reinforced composite laminates with a low-exotherm epoxy powder. An experimental apparatus is developed which heats the laminates from one side while insulating the remaining sides (i.e. approximating one-dimensional heat transfer conditions). The experimental results are analysed and used to validate process models for the epoxy powder system. Process simulations are performed to analyse the influence of material format, laminate thickness change, and heating methods (i.e. one-sided heating vs two-sided heating, and heated tooling vs oven heating). It is shown that epoxy powder eliminates the risk of ‘thermal runaway’, but thermal and cure gradients persist for a conventional processing cycle. Methods to inhibit the evolution of these gradients are explored using process simulations. These methods include modifying the temperature cycle and using multiple epoxy powders with varied latent curing properties

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