Enhancing Interfacial Adhesion Between Copper Mesh Heating Element and Polyamide 66 in Induction Welding of Carbon Fiber/Polyamide 66 Composites via Ozone Treatment

ABSTRACT Induction welding of thermoplastic composites has emerged as an effective technique for lightweight structural assembly, where metallic mesh heating elements (HEs) enable localized and controllable heating. However, untreated HE exhibits poor compatibility with polymer matrices, resulting in weak interfacial adhesion. In this study, copper mesh HEs were subjected to ozone oxidation treatment for various hours to modify surface characteristics and improve bonding with carbon fiber/polyamide 66 (CF/PA66) composites during induction welding. Surface analysis revealed the progressive formation of Cu 2 O, porous CuO, and Cu 2 (OH) 2 CO 3 layers, which enhanced surface roughness and free energy. The joint fabricated with 5 h treated HE exhibited a maximum lap shear strength (LSS) of 44.8 MPa, showing a 34.9% increase over the untreated sample, attributed to improved wettability and mechanical interlocking from the porous CuO layer. However, excessive oxidation (≥ 7 h) caused decomposition of Cu 2 (OH) 2 CO 3 during welding, generating gases that formed interfacial voids and degraded joint quality. Cross‐sectional and fractographic analysis confirmed a deeper elemental interdiffusion zone and a transition in failure mode from HE debonding failure to HE tearing failure under optimal conditions. These findings demonstrated that ozone treatment of copper mesh was an effective strategy to enhance interfacial bonding performance in thermoplastic composite induction welding.