Drapability of dry textile fabrics for stampable thermoplastic preforms

Sandwiches based on stampable foam core and face sheets offer potential for cost-effective applications. Since the formability of such sandwich structures mainly depends on the drapability of the face sheets, the deformation behaviour of several types of textile preforms was evaluated. Glass fibre fabric preforms in the form of plain weave, twill, crowfoot and eight-harness satin as well as warp and weft-knitted architectures were studied. The tensile properties of the dry fabrics at various orientations and the locking angle of woven fabrics in the bias direction were determined. An analytical model is proposed to relate the fabric parameters to the locking angle. Drapability tests were performed on several woven and knitted fabrics in order to relate the forming energy to the preform architecture. Due to their high drapability and low forming energy, warp-knitted structures were selected as textile reinforcement for the sandwich face sheets.