Modeling and analysis of manufacturing of thermoplastic matrix continuous fiber composites using particle impregnation

Thermoplastic matrix composites are an attractive alternative to traditional thermoset matrix composites. They offer improved toughness, can be thermoformed and remolded after initial molding, have a virtually unlimited shelf life, and don't omit harmful volatile organic compounds (VOC's) during the molding process. In this work a new manufacturing process to produce thermoplastic matrix composites has been developed. In this method, fabric is impregnated with a thermoplastic resin powder using a cavity mold and vacuum pressure to draw a suspension of water and resin particles through the fabric. Then, the particle-impregnated fabric is dried in an oven and consolidated using an autoclave or heated hydraulic press.;A process model for both phases of the manufacturing process has been formulated. In the first phase, a filtration coefficient was characterized which is a function of the concentration and the shear rate of the suspension for a selected fiber architecture and particle size. This allowed us to predict the deposition rate of the particles as a function of process variables. The outcome of this phase was coupled to the second phase of consolidation by developing a microscopic model for impregnation of fiber tows with the deposited resin under a chosen cycle of heat and pressure in an autoclave or a press. Important manufacturing parameters have been identified and their role in the outcome of the composite quality in terms of resin, fiber and void content is explored. Each step of the model was validated with a set of experiments.;This particle impregnation model was used to fabricate composite panels with different void fractions and it was shown that a low void fraction is beneficial in energy absorption applications and the method introduced could tailor the processing conditions to obtain a composite with desired void content. It has also been shown that this process can be used to toughen thermoset matrix composites by "pre-toughening" the fabric prior to injection on the thermoset resin. The effect of various levels of particle loading in the fabric prior to infusion with an epoxy resin was studied by measuring the residual compressive strength after an impact event. Improvement was shown with a moderate particle loading using the particle impregnation method. Thus this method should prove beneficial in applications in which one wants to tailor the resin content or toughening particle content.