Carbon nanotube film-based electrothermal joining technology for GF/PPS composites: Process, interfacial structure, and mechanical properties

Thermoplastic composites possess inherent weldability, which is a key advantage over thermosetting composites and enables the fabrication of complex structural components. In this study, a carbon nanotube film (CNT-Film), fabricated by floating-catalyst chemical vapor deposition, was integrated as a functional heating layer into glass-fiber-reinforced polyphenylene sulfide (GF/PPS) thermoplastic composites. Reliable joining between GF/CNT-Film/PPS laminates was achieved by utilizing the electrothermal properties of the CNT-Film. The experimental results showed that the CNT-Film heating element provided relatively uniform heating during resistance welding, improved the temperature uniformity at the weld interface, promoted resin flow, and mitigated thermal edge effects, thereby contributing to enhanced welding efficiency and improved joint quality. Under the optimized conditions of 290 °C, 60 s, and 0.8 MPa, the lap shear strength and interlaminar shear strength of the welded joints reached 7.1 and 46.2 MPa, respectively. Cross-sectional morphology and EDS analyses revealed enhanced resin infiltration into the CNT-Film and increased interfacial transition layer thickness. Combined with the improved mechanical performance and fracture surface observations, these results confirmed enhanced interfacial bonding between the CNT-Film and PPS. DSC and TGA analyses showed increased local crystallinity at the weld interface, while the overall thermal stability remained unchanged. This study demonstrates the potential of CNT-Film heating elements for resistance welding of thermoplastic composites and provides a promising strategy for reliable joining in high-performance lightweight structures.