Enhancing the properties of metal-composite interface by a nano-TiO2 coating

The application of metal-polymer structures has been restricted by challenges in achieving effective bonding between the two materials. To address this, nano-TiO2 coatings were introduced to improve the interfacial bonding between the treated 6061 Al alloy and carbon fiber-reinforced thermoplastic composite (CFRTP) during the laser joining process. The results highlighted that the joints created with nano-TiO2 coatings achieved significantly higher tensile shear force and strength, reaching 1.43 and 1.37 times the values of those without particles, respectively. This improvement can be attributed to the following factors: firstly, the incorporation of coatings led to an increase in the absorption of hydroxy groups, thereby improving the wettability of the Al alloy, which in turn promoted the formation of hydrogen bonds at the interface. Secondly, the increased surface roughness favored the chemical interaction between the Al alloy and CFRTP, ascribed to the enlarged contact area. Moreover, this change influenced the thermal contact conductance (TCC), thereby changing the temperature at the interface and joining areas of the two materials. Finally, a notable transformation in the failure mode was observed, transitioning from adhesive failure to cohesive failure when compared to joints without nano-TiO2 coatings. This underscored the reinforcing role played by nano-TiO2 particles, providing an innovative solution for enhancing the interface bonding between dissimilar materials.