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UBC Theses and Dissertations

A coupled non-orthogonal hypoelastic constitutive model for simulation of woven fabrics Haghi Kashani, Masoud


Woven fabrics offer a number of advantages compared to their unidirectional counterpart, such as their superior formability and higher out-of-plane stiffness, making this class of materials a decent alternative in leading composite industries such as aerospace and automotive. While their performance merits originate from the interlacing architecture of yarns, this architecture causes some complications toward their reliable analyses; namely the presence of inherent couplings between families of yarns under different deformation modes. Theoretically, the inherent coupling means an arbitrary macro deformation in a given fabric direction can affect the individual effective properties in other directions. This study aims to provide an enhanced understanding of the role of such couplings in the mechanical behavior of woven fabrics. More specifically, the study attempts to identify the underlying multi-scale sources responsible for the coupled mechanical response of woven fabrics. Subsequently, the work introduces a new non-orthogonal hypoelastic constitutive model to reflect the observed coupled deformation mechanisms in woven fabrics. Different modes of coupling are defined and distinguished from the general coupling scheme presented by the Hook’s law. In order to parameterize the model, a comprehensive characterization framework under tension-shear, tension-tension, and shear-tension coupling modes is developed, via a multi-scale analysis. The results show that the first two modes should be closely taken into account in the analyses of fabrics to achieve more accurate predictions of the material response. The attained macro-level characterization results are interpreted at micro and meso levels. Finally, the coupled non-orthogonal model is augmented with a new wrinkling criterion to precisely predict not only the stress-strain response, but also the wrinkling onset of a plain weave in the presence of inherent coupling. The comparison between the experimental and prediction results validates the capabilities of the proposed model. The main practical advantages of including couplings in the analyses of woven fabrics are considered to be (a) more reliable design of the fabric-reinforced composites, (b) better anticipating the shape of deformed fabrics in general, and the wrinkles in particular, and (c) determination of the required tension levels to prevent wrinkling during forming process of fabrics.

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