Textile composites used as structural components have recently attracted more and more attention due to their superior properties and efficient stamping operations. However, formability of textile composite sheets, restricted by failure mechanisms such as wrinkling and inter-yarn slippage, remains as a crucial and challenging issue for stamping operations. From a meso-scale mechanics’ point of view, this PhD thesis presents a comprehensive experimental, theoretical and numerical study on large shear deformation, which is the primary deformation mode during stamping, as well as corresponding failures for woven fabric composite preforms. In-plane large combined shear/tension behavior of continuous E-glass fiber-reinforced thermoplastic Polypropylene (PP) textile composite sheets were cha...[ Read more ]

Textile composites used as structural components have recently attracted more and more attention due to their superior properties and efficient stamping operations. However, formability of textile composite sheets, restricted by failure mechanisms such as wrinkling and inter-yarn slippage, remains as a crucial and challenging issue for stamping operations. From a meso-scale mechanics’ point of view, this PhD thesis presents a comprehensive experimental, theoretical and numerical study on large shear deformation, which is the primary deformation mode during stamping, as well as corresponding failures for woven fabric composite preforms. In-plane large combined shear/tension behavior of continuous E-glass fiber-reinforced thermoplastic Polypropylene (PP) textile composite sheets were characterized by both picture frame and bias extension tests at various conditions. The deformation evolution and corresponding failures relevant to boundary conditions and stress/strain state of the material were identified and analyzed. Through an energy method, theoretical models are proposed to estimate the shear stiffness, load-displacement response, inter-yarn slippage and wrinkling of the textile specimen. General criteria are formulated to predict the failures of composite fabrics of similar textile architectures. FEM was conducted to simulate the material’s large shear behavior and the onset of wrinkling, which shows a good agreement with the experimental results and theoretical predictions. Then, a series of real stamping tests were carried out on plain woven specimen at room temperature, with strain measurement by conductive fiber sensors and marked points directly on the sample, from which the shear distribution and evolution are obtained and the proposed theoretical criterion of wrinkling is validated. Finally, forming parameters and material properties are optimized, and technical recommendations and suggestions are provided to the textile engineering and forming industry to improve the material’s formability in stamping operations.