Laser-Assisted Tape Placement of Thermoplastic Composites: The Effect of Process Parameters on Bond Strength

The manufacturing process for high performance composite materials is typically slow due to labour intensive lay-up processes followed by long cure cycles of thermosetting resins. Thermoplastic materials be can processed by fusion bonding, a welding process based on the diffusion of polymer molecules across the bond interface at elevated temperatures. This process can be orders of magnitude faster than a typical thermoset cure. Furthermore, when coupled with a placement technology such as automated tape placement (ATP) or filament winding, the composite can be bonded in situ as it is placed. The part is ready for finishing as soon as placement or winding has completed. This approach shows much potential for flexible and automated manufacture of lightweight and high performance automotive structures, including high pressure storage vessels for gaseous fuels. The placement rate must be maximised for production, however maintaining composite quality is nontrivial due to the highly dynamic behaviours at the nip point. A small parametric study was performed to investigate the effects of laser power and consolidation force. A laser-assisted tape placement system was instrumented with temperature and pressure sensors so as to measure the temperature and pressure profiles experienced at the bond interface in the nip point region. The recorded temperature and pressure profiles were fed into a bonding model to predict the resulting strength. Mechanical tests were performed on Carbon/PEEK lap shear samples and compared with strength predictions.