A multiscale analysis of forming induced wrinkles in woven composite preforms

A multi-scale analysis of forming induced wrinkles in woven composite preforms is conducted. The main objective of the present thesis is to propose an analytical model for the prediction of a class of forming induced wrinkles. In this research, wrinkling phenomenon in woven fabrics is divided into two distinct classes based on the nature and mechanism of formation, namely shear wrinkling (i.e., developed as a result of large shear deformation) and non-shear wrinkling (i.e., developed due to longitudinal contraction of the length of the fabric strip). Shear wrinkling as one of the most critical defects in the draping of woven fabrics is investigated in this study. To develop an analytical model for the prediction of shear wrinkling, an in-depth investigation is conducted to scrutinize the mesoscale mechanisms of woven fabrics during shear deformation. It is revealed that shear of woven fabrics occurs through two distinct deformation modes (i.e., trellising mode and pure multi-scale shear mode) depending on the boundary conditions applied to the fabric. In accordance with the deformation mode of woven fabrics, analytical equations are derived to predict the onset of shear wrinkling of the fabrics. Experimental investigations are conducted to assess the accuracy of the analytical model. Afterward, the analytical model for the prediction of shear wrinkling is implemented into ABAQUS Finite Element (FE) package as wrinkling indicator/predictor to improve the accuracy of the FE results. Furthermore, a parametric study is carried out to determine the effect of fabric and process parameters on the resistance of woven fabrics against wrinkling.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat