Impregnation of compressible fiber mats with a thermoplastic resin, Part II: Experiments
transverse direction is investigated with application to the Glass Mat reinforced Thermoplastics (GMT) lamination process in a double belt press.Amodel proposed in Part I to simulate the kinetics of impregnation and the evolution of the fiber volume fraction profile as the resin front progresses across the fiber mat, as well as after macro-impregnation is complete, is further developed to include micro-impregnation effects. The predictions are compared with experimental results obtained using model systems such as polyethylene glycol and glass fiber mats, as well as an industrially relevant system consisting of polypropylene and glass fiber mats used in the production of GMT blanks. It is shown that significant compression of the fiber mat may occur during impregnation, with subsequent relaxation on a much longer time-scale. Also, fiber bundle impregnation generally occurs after macro-impregnation is complete, the driving force being the local pressure in the resin around the bundles, dictated by the local state of compression of the mat. The model is then used to provide guidelines for optimization of the preform impregnation conditions for a given material configuration.