Effects of Yarn Undulation on the Stress and Deformation of Textile Structural Composites

This paper reports the effects of yarn undulation on the stress and deformation of plain weave composites. The findings from a number of sources² are reviewed and compiled here. Existing micromechanical analyses of woven fabric composites have been conducted using mostly either simplifying mathematical models or elaborate three-dimensional finite element analysis. For example, Ishikawa and Chou proposed the mosaic model, crimp model, and bridging model for analyzing the thermoelastic and failure behavior of woven fabric composites. On the other hand, finite element analysis by Whitcomb and Foye, for example, can provide detailed stress analysis under specific boundary conditions. The recent work of Ito and Chou expands the analytical capability to modeling of the strength and failure behavior of woven fabric composites. In their studies, the geometrical characteristics of yarn shape, laminate stacking configuration, fiber volume fraction, and yarn packing fraction are investigated using three-dimensional micromechanical models. Based on the geometrical characteristics, an iso-strain approach is then developed to predict the elastic properties, local stress distributions, and failure strengths under tensile loading for four laminate stacking configurations: a single lamina, an iso-phase laminate, an out-of-phase laminate, and a random-phase laminate.