Effect of low‐pressure plasma treatment on the adhesive performance of <scp>PEEK</scp> and co‐polymerized <scp>PAEK</scp> composites

Abstract The use of high‐performance thermoplastic composites has become an increasing trend in the manufacturing of modern aerospace structures due to their environmental and economic advantages. However, the effects of low‐pressure plasma treatment on their surface properties and adhesive joint performance of poly aryl ether ketone (PAEK) composites have not been fully investigated. This study employed a poly ether ether ketone (PEEK) and a new co‐polymerized PAEK to respectively manufacture carbon fiber reinforced polymer (CFRP) composites. Oxygen plasma was used to activate the CFRP surfaces, and the effect of different plasma treatment parameters on their surface morphology, chemical composition, and wettability was studied. The single lap joint strengths of CF/PEEK‐CF/PEEK and CF/PAEK‐CF/PAEK joints were measured. The effects of plasma treatment on the two thermoplastic composites were compared. The results show that a moderate level of plasma treatment was effective in removing surface contaminations, improving wettability, modifying surface micro‐nanostructure, activating surface chemistry, and thus increasing the joint strength. The PAEK matrix composite usually produced joints with higher strength compared to the PEEK matrix composites. The higher toughness of the PAEK matrix composite enabled it to withstand higher energy plasma treatments without incurring the deleterious effect of fiber exposure on the surface. Highlights A newly co‐polymerized PAEK differs from a PEEK in surface treatment and adhesion. PAEK had a higher toughness than PEEK, and it was more difficult to be eroded by plasma. The present CF/PAEK joints showed higher SLS strengths than CF/PEEK joints. After appropriate treatment, SLS strength of CF/PAEK joints reached 36.6 MPa.