Effect of plasma treatment parameters on the interfacial joining strength of overmolded hybrid fiber reinforced thermoplastic composites

In this study, hybrid fiber reinforced thermoplastic composites (hybrid thermoplastic composites) with high interfacial joining strength were fabricated using a plasma treatment strategy and injection overmolding technique. A series of experimental investigations were carried out to ascertain the effects of various plasma treatments on the interfacial joining strength of the overmolded hybrid composites. Test results reveal that compared with the untreated continuous fiber reinforced thermoplastic (CFRT) substrates, the surface roughness of the CFRT substrates treated by plasma with air for the 10 min-160 W set-up increases by 28.7%, the contact angle decreases by 50.5%, the silicon and fluorine are effectively removed, and the content of polar functional group increases remarkably, which bring about the increase of 24.76% of the interfacial shear strength of the overmolded hybrid composites. Further increase of plasma treatment time does not contribute to increase the interfacial shear strength of the overmolded hybrid composites. The interfacial shear strength at 60 W is 6.38% higher than that at 160 W, which is ascribed to the increase of the oxygen-containing functional group content. Compared with the air and nitrogen plasma treatment, the interfacial shear strength of the overmolded hybrid composites after oxygen plasma treatment reaches the maximum value.