| Considerable effort has been made by researchers to evaluate the effectiveness of various textile composites. However, reports on the integrated analysis from processing and microstructural variations of preforms to the performance of composites is very limited. In order to acquire more comprehensive understanding of textile composites, the processing-microstructure-performance relationships for a variety of material systems, reinforcing schemes and processing technologies should be established. In this dissertation, emphasis is placed on the integrated analysis of 3-D angle-interlock woven, 2-step braided, and track-and-column braided composites. The analysis includes the geometric models of preforms, identification of key process parameters and processing windows due to limiting geometries of yarn jamming, and prediction of elastic properties of composites. The coordinate transformation and the volume averaging based upon the combined stiffness and compliance method are utilized in the prediction of elastic constants of various textile composites. The macro-cell approach is effective in characterizing the complex structure of 3-D composites, which has no repeatable unit cells in the thickness or width directions. Mechanical tests were conducted to verify the model prediction and to assess the stress-strain behavior of the composites. The parametric studies are carried out to identify the effect of various geometric and process parameters on the elastic response of the composites. The performance maps for 3-D woven and 3-D braided composites demonstrate that a wide range of elastic properties can be achieved by varying the geometric and process parameters. Through the construction of performance maps, the relative effectiveness of various reinforcement concepts can be assessed. Performance maps will enable composite structural designers to make a judicious selection of fiber and matrix systems, preform geometries and microstructures, and processing conditions for meeting specific composite performance requirements. |
