RAPID CONSOLIDATION OF UNIDIRECTIONAL GRAPHITE THERMOPLASTIC RIBBON/

An inexpensive apparatus was designed to simulate some features of on- the-fly thermal welding in robotic placement of thermoplastic prepreg ribbon. Studies of a polyimide oligomer have shown how ply/ply weld st rength depends on weld time, temperature, and pressure. Examination of the data at very short effective times reveals a contribution from we tting amounting to 20 percent of the ultimate strength followed by the expected time((1/4)) behavior. Welding at low pressures produces high levels of intra-ply voids. Pressures up to 1.7 MPa (250 psi) produce more consistent welds and virtually eliminate voids. This has permitte d a study of the conditions required for achieving the limiting ply/pl y cohesive strength in simulated tow placement.