Modelling the thermo-elastic properties of skewed woven fabric reinforced composites

Abstract

Woven fabrics prove to be a very convenient fibre reinforcement when prepreg layers have to be draped on to double curvature moulds. The process of draping causes the angle between the warp and weft yarns to vary over the product with this double curvature. As a result, the thermomechanical properties of the fibre reinforced composite material show a corresponding distribution. These thermo-elastic properties must be known in order to predict the shrinkage\ud and warpage of the product. Normally, composites consist of multiple fabric layers. These layers are oriented and skewed differently, and each contributes to the overall composite properties. Therefore, in order to predict the overall thermo-elastic properties of the composite as a whole, the properties of each individual layer must be known. In this paper, the inplane thermo-elastic\ud properties of a woven fabric reinforced composite with an arbitrary weave type are analysed as a function of the skew angle, using micromechanics. Three different levels of material structure are modelled, the micro-, the meso- and the macro level. The inplane thermo-elastic properties of four different basic elements are determined at the micro level, using geometrical shape functions and a two-dimensional thermo-elastic model. The inplane properties of one fabric layer are determined at the meso level, using the fabric pattern and the properties of the basic elements. At the macro level the homogeneous properties and warpage of woven fabric composites are considered. Here the composite structure and the properties of the individual layer are used. The method proves to be a convenient way to model the skew deformation of the woven fabric composite and the resulting variation in the thermo-elastic properties. The theoretical predictions are verified by experiments on multiple-layered satin 5H woven fabric composites