Experimental investigation, using 3D digital image correlation, into the effect of component geometry on the wrinkling behaviour and the wrinkling mechanisms of a biaxial NCF during preforming

Abstract

This study investigates the effect of component geometry on the wrinkling mechanisms of non-crimp fabrics (NCFs) during preforming. Using 3D digital image correlation, the wrinkling behaviour of a biaxial NCF formed over four benchmark geometries is characterised and related to the NCF’s surface strains. It is shown that the effect of geometry on the severity of wrinkling is highly significant and that there are two possible wrinkling mechanisms (via shear lockup or via compression) for large wrinkles to occur, which are consistent across geometries. Importantly, an increase in local shear resistance (due to the stitches in this case) is shown to cause severe wrinkles in textile reinforcements at low shear angles due to lateral fabric compression. Additionally, tow wrinkling in NCFs is shown to correlate with local tow compression. Thus, it is not always valid to assume that fabrics are only likely to wrinkle during forming due to excessive shearing.