Diaphragm forming of continuous fibre reinforced thermoplastics:: influence of temperature, pressure and forming velocity on the forming of Upilex-R® diaphragms

In the diaphragm forming process, the thermoplastic composite sheet is clamped between two high temperature thermoplastic diaphragms. In the present study, the influence of temperature, pressure and forming rate on the deformation of high temperature PI diaphragms (Upilex-R(R), Ube Industries) is described. At temperatures below 275 degreesC the upper diaphragm slides over the bottom diaphragm and shows a more global deformation, above 305 degreesC, the upper diaphragm cannot slide over the bottom diaphragm and deforms in the same manner. The region 275-305 degreesC is a kind of transition region between the previous two temperature ranges. A hydrostatic pressure of I bar turned out to be sufficient to deform the diaphragms, therefore, no influence of pressure was observed. The deformation of the bottom diaphragm is independent of forming rate, while the upper diaphragm showed some dependence. (C) 2002 Elsevier Science Ltd. All rights reserved.