Geometric modelling of industrial preforms: warp-knitted textiles

The processing properties of fibrous preforms and the final properties of L iquid moulded composite parts are strongly related to the internal architec ture of the preforms. The architecture of a preform is determined by the in dividual textile layers from which it is made. In order to calculate the pr ocessing and final properties in the same way over all the volume of a pref orm or part made from different types of textile, some sets of equations th at generate similar definitions of the textiles from their manufacturing pa rameters are required. The similarity of these definitions is assessed thro ugh a series of criteria stated in a previous paper by the present authors; definition modules for woven and braided textiles were also presented in t hat paper. This paper presents a definition module, or a set of equations, that generates similar definitions for non-crimp reinforcements assembled b y warp knitting; the equations also apply for the stitched threads used to assemble multiple-layer preforms. The definitions obtained from this module obey the criteria mentioned previously. The sets of equations presented in both papers cover most technical textiles; similar sets of equations can b e created for speciality reinforcements and applied to the calculation of d iverse physical properties of the preforms and parts. As an example, this p aper discusses the mapping of the voids which are defined between the rows and threads of non-crimp stitched reinforcements.