Thermal Stress Mitigation and Mechanical Strength Enhancement in CFRP-Al Bonded Joints via Ply Curving Termination

Joining carbon-fiber-reinforced plastics (CFRPs) and metals is a critical technology in the aerospace industry. Therefore, a strong and reliable composite-metal adhesive bonding technology is necessary for future aerospace applications. This study focuses on the Ply Curving Termination (PCT) method, which locally modifies the fiber orientation of CFRPs. By reducing stiffness and aligning the thermal expansion coefficient at the CFRP edges to that of the metal, the PCT method effectively decreases stress concentrations in the adhesive layer. Cooling and tensile tests were conducted to demonstrate that PCT can prevent disbonding in CFRP-Al joints under cryogenic environments and suppress overall failure of the bonded region under tensile loading. Finite element analysis was used to evaluate stress distributions under cooling and tensile conditions, revealing that the effectiveness of PCT depends on the specific thermo-mechanical conditions applied to the composite-metal joint. In the most effective case, PCT increased the disbond strength of CFRP-Al joints by 74%. These findings highlight the potential of PCT to enhance the structural reliability of CFRP-metal joints, offering a promising solution for future aerospace applications.