UNDERSTANDING THE EFFECT OF IN-PLANE FIBER WAVINESS ON DAMAGE BEHAVIOR OF CURED WOVEN COPOSITES

On account of merits such as enhanced fracture toughness and out-of-plane impact resistance due to interlaced fibrous architecture, woven composite materials are gradually being regarded as a superior alternative to unidirectional composites (UDs) in numerous industries. However, the interlaced architecture of fibers leads to complexities such as misalignment and coupling between warp and weft yarns upon the mechanical loading of dry and consolidated woven fabrics. Employing Digital Image Correlation (DIC) and microscopy, this article is an attempt to present a detailed experimental investigation into the mechanical behavior of a consolidated twill woven PP/glass lamina under tensile loading in warp and weft directions so as to assess the unbalancedness effect resulting from in-plane waviness of warp and weft yarns. Results showed that the woven composite specimens under tension in the weft direction behaved linearly up to final failure analogous to that of unidirectional composites whereas they showed a non-linear response with less stiffness under tension in warp direction in the early steps of loading, and subsequently encountered failure modes in 'multiple' steps. Moreover, the imaging data revealed that although the induced failure types (matrix cracking followed by fiber fracture) are similar between the warp and weft directions, the source of their failure modes as well as the corresponding stress-strain values are substantially different, even if the fabric would have been initially presumed balanced. The aforementioned observations were further verified via statistical hypothesis testing with alpha=5%.