CHARACTERISATION OF PREPREG TACK ON DIFFERENT SURFACES TO AID AUTOMATED MATERIAL PLACEMENT

To aid optimising process parameters in the manufacture of composite components employing automated material placement processes, tack for a commercial uni-directional carbon fibre/epoxy prepreg tape on different surfaces was characterised experimentally. A test fixture, recently designed for measurement of tack between a prepreg specimen and a rigid tool surface, was adapted to enable measurement of prepreg-prepreg and FEP-prepreg tack. For different surface pairings, tack was measured at a range of temperatures and feed rates. Employing time-temperature superposition based on rheological data for the resin in the prepreg allows the tack force to be shifted to a reference temperature to create a tack master curve. Maximum prepreg-prepreg tack is significantly higher than the corresponding maximum prepreg-steel tack. At a given reference temperature, both occur at approximately the same shifted feed rate. Maximum FEP-prepreg tack is significantly lower than the corresponding maximum prepreg-steel tack. At the same reference temperature, it was observed at shifted feed rates one order of magnitude smaller than for prepreg-steel tack. Measurement of pre-pregprepreg tack at different inter-ply angles indicated that tack increases continuously with increasing inter-ply angle. Shifting of tack data also allows prediction of the feed rate for maximum tack at any temperature, thus contributing to the optimisation of process parameters in achieving maximum production rates and product quality.