Instrumented thermoforming of advanced thermoplastic composites. III: Relative performance of various prepregs in forming double curvature parts
Anindya Dutta, Mukerrem Cakmak · Polymer Composites · 1991
Abstract Thermoforming of a double curvature hemispherical cap‐shaped part from different continuous carbon fiber‐reinforced thermoplastic composite prepregs has been investigated. A novel three‐piece matched die mold was used for shaping the prepregs directly from 16‐ply unconsolidated lay‐ups. For poly(ether ether ketone) (PEEK)‐based prepregs, PEEK/graphite fiber unidirectional tapes and commingled knitted three‐dimensional fabric yielded parts that possessed good shape conformity and were free of any major delamination. Encouraging results were also obtained for modified polysulfone (PXM‐8505) based unidirectional fabric as well as PEEK/graphite knitted bidirectional fabrics. Several other prepregs performed rather poorly in forming acceptable quality parts. Fiber alignment was found to be better for fabric prepregs than unidirectional tapes. Both stretching and “draw in” of the material occur during deformation, even though the relative contribution depends strongly on the prepreg form. Our thermoforming studies suggest a cycle time of 10 min or less to form good quality parts, which is an attractive feature, considering that cycle times are typically several hours for conventional thermosetting resins.