Metallization of carbon fibre reinforced polymers by cold spray

Carbon fibre reinforced polymer (CFRP) is a very competitive alternative to aluminum for aircraft structures for lightweighting purposes, but this leaves vulnerability against lightning strike. Cold spray is one coating approach to metallize the polymers, making them lightning strike proof. The aim of this work is to investigate the viability of metallizing aircraft quality CFRPs by cold spray. Copper, aluminum and tin were cold sprayed onto the CFRPs with both a high-pressure and a low-pressure cold spray system. A number of different combinations of the gas pressure and gas preheating temperature were used for the cold spray process. Erosion was found to be the key obstacle to developing continuous coatings on the CFRP substrates with the high-pressure system. On the other hand, continuous tin coatings were successfully obtained on CFRP with the low-pressure system, due to the very soft tin coating the substrate through a “crack filling” mechanism. Based on the results, it was proposed that when cold spraying metals on CFRP, it is necessary to differentiate between the development of the first layer and the build-up of subsequent layers. Last but not least, the effect of particle velocity and gas temperature was discussed and the deposition window of tin on CFRP was developed.