Investigation of the interphase mechanisms and welding behaviour of fast-curing epoxy based composites with co-cured thermoplastic boundary layers

Abstract

This study focuses on investigating thermoplastic polymers and their interphase behaviour with the fast-curing epoxy system Araldite LY3585/Aradur 3475. The three compatible thermoplastic polymers poly(methyl methacrylate) (PMMA), amorphous polyamide (PA12TR90), and poly(hydroxy ether) (phenoxy) were chosen to determine their affinity and interphase formation with the epoxy system. The final concept involves the use of a thermoplastic as a boundary layer on top of the epoxy to establish a connection between two joined parts by resistance welding. The thermoplastic boundary layer was generated by co-curing during the curing process. The experiments resulted in a high compatibility between phenoxy and PMMA in the selected epoxy system which leads to excellent mechanical properties after welding. Phenoxy showed the strongest joints, with an average lap shear strength of 25 MPa, demonstrating the high potential of this joining technique for industrial applications in the automotive and wind energy fields.