Finite Element Analysis of a Biaxially Loaded Woven Fabric Composite Laminate With a Central Hole

Abstract

Textile composites are structural materials reinforced by a network of fibers and are formed by processes such as braiding, weaving, or knitting. Woven fabric composites are two dimensional constructions where the warp and fill fiber tows are woven into each other to form a layer. The layers are impregnated, stacked in predetermined orientations and cured to obtain composite laminates. The composite laminates thus formed have good properties in mutually orthogonal directions as well as more balanced properties and better impact resistance than the unidirectional laminates. Woven fabric laminated composites are likely to play a key role in modern design, principally owing to their attractive strength to weight and stiffness ratios. To compete effectively with other materials, these woven fabric laminates are often utilized in plate form with cutouts in them. Analytical models that predict the moduli, Poisson’s ratios from the weave architecture and the properties of the constituents are desirable. In this paper, a plain weave model is presented to develop the constitutive relationships (i.e., A, B and D matrices). The results from the plain weave model are used in conjunction with the classical laminate theory and linear finite element model of a woven fabric laminate to predict the stress concentration around a central hole. A graphite/epoxy material system was used. The woven fabric plies were assumed to be of constant thickness and were arranged symmetrically about the mid plane. In addition to woven fabric plies, regular unidirectional plies were also stacked at different angle orientation. The square plate with a hole was then subjected to biaxial in-plane loading. The stress concentration factors were determined by computing the ratio of stresses around the hole to those without hole at the same location.