Fusion bonding of thermosets composite structures with thermoplastic binder co-cure and prepreg interlayer in electrical resistance welding

• Thermoplastic binder co-cure and prepreg interlayer methods were integrated in fusion bonding
• Thermoplastic binder was co-cured onto the surface of the carbon fiber reinforced epoxy composite laminate
• The prepreg interlayer was designed as heating element made of carbon fiber reinforced binder prepreg
• The GIC of the fusion bonded specimens is significantly influenced by the binder and the heating element
• Three types of failure pattern in the fusion bonded specimens can be visually and microscopically observed.

A new concept combining both thermoplastic binder co-cure and prepreg interlayer is proposed and investigated for fusion bonding of thermosets composite structures. Three different thermoplastic binders were co-cured respectively onto the surface of the carbon fiber reinforced epoxy (CF/Epoxy) composite laminates to form an auxiliary medium for electrical resistance welding. The carbon fiber reinforced binder (CF/Binder) prepreg interlayer, which is compression molded with a single layer of carbon fiber fabric sandwiched between two binder films, was designed as the heating element. Double cantilever beam (DCB) specimens were fabricated by fusion bonding of the CF/Epoxy composite laminates. The influence of the thermoplastic binders and the CF/Binder prepreg interlayers on the mode I interlaminar fracture toughness (GIC) and the morphology of the fracture surface were studied respectively by double cantilever beam test and scanning electron microscope. The results indicate that a maximum average delamination strength GIC of 1879.6 J/m2 was obtained in the case of the AX8900 binder welded specimens using twill weave fabric heating element. Three types of failure pattern can be visually and microscopically observed, i.e. interfacial-type failure, cohesive-type failure and interlaminar-type failure.

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