Defect reduction in the double diaphragm forming process

Diaphragm forming is one potential method for implementing automation in the production of low cost preforms for high volume composite applications. Components with double curvature have been produced using three different processes; press forming, double diaphragm forming and single diaphragm forming to compare preform quality. Press forming was found to produce the best quality preforms, whilst single diaphragm forming produced the worst, as the single diaphragm did not constrain the material sufficiently. Using risers in the diaphragm forming process was investigated to reduce defects in preforms without affecting the mechanical properties of the finished part. It was found that out of plane wrinkling defects could be successfully alleviated, but areas of fabric bridging remained.