The large deformation behavior of woven fabric and microstructural evolution in formed textile composites

Specific performance advantages are routinely demonstrated with advanced composites in structural applications. An inability to efficiently manufacture these materials however, is greatly impeding their widespread implementation in engineering design. Resin transfer molding processes have a potential to provide increased volume production of formed textile composites. These processes rely on the unique ability of fabric materials to achieve the large deformations required in forming operations. Many of the issues that remain to be resolved with such processes, particularly for components with multiple curvature, are related to the initial step of forming dry fabric about the mold surface. Simulation of this procedure would provide a tool with which designers may anticipate the forming induced evolution of microstructure and the development of defects such as wrinkles.; Development of a simulation tool for fabric forming requires characterization of the mechanical properties of fabrics. To date, the constitutive behavior of fabric at large deformation has not been understood. In this dissertation, a method of predicting the deformation dependent average properties for plain weave fabrics is presented. Further, the effect of fabric architecture on these properties is demonstrated. The fabric behavior is characterized by an initial highly compliant response followed by rapid stiffening. At levels of deformation for which rapid stiffening occurs, defects such as wrinkling are a necessary concern.; A predictive description of the evolution of fabric microstructure is also provided. If the mold geometry and initial, undeformed fabric architecture is known, the forming induced evolution of local microstructure may be defined. In components with multiple curvature, the configuration of representative microstructural elements will vary from cell to cell within a ply. Average properties of formed fabrics or formed fabric composites will then vary slowly in the macroscale. The slow variation of composite mechanical properties and of preform permeability are investigated as examples. Through investigation of the effect of fabric architecture, and its evolution, on the fabric response in forming operations, fabric selection and tool design may be guided.