Transport Phenomena and Microstructure Development in Thermoplastic Composites Processing

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In rapid and continuous manufacturing situations such as filament winding and pultrusion, the goal is to obtain a high volume fraction of the fibers with uniform resin impregnation and a structure that is well bonded and free from voids and residual stresses. Hence, the mechanics of resin impregnation under non- isothermal conditions, the mass diffusion of the polymer across the interfaces of impregnated fiber bundles and the changing crystallinity as the structure solidifies are key phenomena during the processing of such composite materials. This research will develop a systematic understanding of the mechanisms of transport of mass, momentum and energy in a continuously deforming anisotropic porous media of aligned fibers and examine their interactions and estimate their relative importance. This can then be integrated into process models which will allow calculation of the fiber volume fraction, void fraction and residual stresses as a function of the manufacturing process, material form and processing conditions. The approach will involve model experimental studies in carefully controlled laboratory conditions, which will serve to identify and understand the physics of flow of shear thinning viscous fluids and will form the basis for theoretical modeling. Simultaneously, the role of transport equations at the microscopic level in a cell geometry representative of the anisotropic medium will be explored. The intent being to develop a macroscopic process model based on microscopic analysis that will relate the fiber volume fraction, void content and residual stress distribution of different material forms and processing conditions. To establish the validity and usefulness of the formulated process models, experiments in actual processing environment encompassing of filament winding and pultrusion processing techniques will be carried out. The study will allow the production of more uniform, high strength components from composite materials.