Compression in the processing of polymer composites 2. Modelling of the viscoelastic compression of resin-impregnated fibre networks

Abstract

This paper presents a study of the viscoelastic compression of resin-impregnated fibre cloths. The experiments included a type of plain-weave cloth and two types of resin, an epoxy behaving approximately as a Newtonian fluid and a polyester following power-law, non-Newtonian behaviour. The experimental studies of viscoelastic compression included a review of compression tests at two different compression speeds, and also compression hysteresis tests and pressure relaxation tests. The mathematical analysis covered the development of a viscoelastic model in which the total applied pressure during compression was split between the pressure to compress the assembly of fibre cloths and the pressure required for the resin flow through the deformable, porous medium. It considers elastic and viscoelastic effects from the fibre medium, and viscous and elastic effects from flowing resin. Regarding the type of resin, it includes modelling of both a Newtonian and a non-Newtonian fluid. The model was fitted to the experimental data for wet compression for both types of resin and yielded best-fit values for parameters from the Carman–Kozeny equation and the non-Newtonian type of Darcy’s law, for the plain-weave fabric used.