Two-dimensional to three-dimensional dry fibre preforming

Preforming is the process of converting two-dimensional (2D) intermediate fibre products, such as fabrics and mats, into complex three-dimensional (3D) shapes to resemble the geometry of the final component. Preforming is a necessary step for all liquid composite moulding processes, such as vacuum infusion and resin transfer moulding, to ensure that the fibres are aligned and assembled to satisfy the in-service stresses. Preforming can typically be implemented through either hand lay-up, press tool forming, or diaphragm forming. The formability of a fabric material is dominated by shear deformation and material sliding, as the primary yarns are inextensible and therefore have to either rotate at the yarn crossover points, slip relative to one another, or slip together to conform to the surface of the mould tool. Automation is the key to reducing cost and increasing production volumes, but defects such as fabric wrinkling and bridging are difficult to avoid without touch labour. This chapter focuses exclusively on 2D to 3D dry fibre preforming, highlighting process developments to help mitigate forming-induced defects.