| Thermoforming of thermoplastic woven fabric composites offers great advantages to the automobile industry for future production of structural parts, such as bumpers, floor pans and truck beds. A woven fabric's main mode of deformation during forming is shear, allowing it to take on shapes of double curvature. Shear deformation may be influenced by temperature, rate, matrix viscosity, fabric architecture and material type. Proper material characterization of thermoplastic woven fabrics is important for accurate modeling of thermoforming for future process optimization efforts.; In this thesis, extensive testing with the use of a trellis shear frame is discussed. Conditioning the fabric several times prior to testing was found to minimize shear-testing non-repeatability resulting from fabric misalignment. Correlation between test fixtures and fabric of different sizes was established by normalizing data with respect to area, suggesting that the number of yarn crossovers, as represented by the area, within the material is critical. Once test method verification is established, material characterization at elevated temperature and rates was completed. With an accurate understanding of the material behavior at varying temperatures and rates, the applicability of a semi-empirical ideal fiber-reinforced fluid model was examined for future process optimization. |
