Mapping of tubular woven composite preforms on to doubly-curved surfaces

This paper deals with the drape behaviour of tubular woven fabric hoses over doubly curved mould surfaces. The primary aim of this analysis is to predict the alignment of the constituent fibres over the mould surface, which in composites-based applications directly influences the quality of the final product in terms of its structural homogeneity and mechanical properties. Previous work in the area has resulted in algorithms to map the fibres of a flat woven fabric over open surfaces using the shear deformation theory of a woven lamina. The present paper first applies these algorithms to map a flat fabric on to a doubly curved tubular surface and determines the outline of an equivalent tubular fabric preform needed to cover the surface. It is noted that using such a mapping, even to produce a simple u-bend tube requires the tubular preform to have varying cross-section, which is difficult to manufacture. Subsequently, specific algorithms are developed to map a straight tubular hose over a bent and twisted tubular section. Using basic principles of mechanics, models have been derived to map the mesh of fibres over geodesic paths on the curved surface. It is noted that shear deformation plays little or no role but fabric extension and buckling play major roles. The resulting mapping algorithm has been applied to several shapes of varying complexity and experimental validations have been performed.