FLEXURAL PROPERTIES OF SEWN CARBON-FIBER COMPOSITES

This paper examines the potential for sewing layers of composite prepreg material together to achieve improved flexural performance. Layers were hand laid-up in the conventional way, and, before being cured in an autoclave, were sewn together by using a range of reinforcing threads. A small but significant improvement in the flexural properties was achieved, particularly when layers were sewn together by using a ball-point needle with a fine polyester-fibre yarn. In parallel, a slight loss of maximum deflection at failure was shown, and this may have implications on the energy-absorption capabilities of such composites. Considerable limitations were found in terms of the amount (%) of through-the-thickness reinforcement which could be inserted by this particular method. Severe problems were also encountered during the sewing process as a result of resin pick-up.