Effect of Low-Pressure Plasma Treatment on the Adhesive Performance of Peek and Co-Polymerised Paek 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-polymerised PAEK to respectively manufacture carbon fibre reinforced polymer (CFRP) composites. Oxygen plasma was used to activate the CFRP surfaces, and the effect of different plasma treatment parameters on the surface morphology, chemical composition, and wettability of the composites were studied through SEM, XPS, and contact angle testing. The single lap joint strengths of CF/PEEK-CF/PEEK and CF/PAEK-CF/PAEK joints were measured. The differences between the PEEK and the PAEK matrix in the CFRPs after plasma treatment were investigated. The results show that a moderate level of plasma treatment was effective in removing surface contaminations, decreasing contact angle, 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, compared to the PEEK matrix composite, enabled it to withstand higher energy plasma treatments without incurring the deleterious effect of fibre exposure on the surface.

Keywords: A. Polymer-matrix composites (PMCs), A. Thermoplastic resin, B. Adhesion, D. Surface analysis, E. Surface treatments