Effect of thermal-mechanical conditions on strength of silanized Al alloy/CFRTP hybrid joint made by thinning-controlled hot pressing

Abstract

The strength of thermal-assisted joined metal and carbon fiber-reinforced thermoplastics (CFRTP) is dependent on physical and chemical interactions at the joining interface, which are strongly influenced by heat and pressure. Currently, there is a lack in deep research on effect mechanism of changeable pressure on the joining quality, limiting the joining condition optimization of the thermal-assisted joining process. In this study, an improved hot-pressing joining process with added thinning displacement control was adopted to study the effect of the joining pressure on the structure and strength of the interface between a silane-treated Al alloy and three CF-Polyamide-6 (CF/PA6). A high-strength, thinning-controlled lapped joint of Al and CF/PA6 could be realized by the proposed process, regardless of the fiber volume fractions in CF/PA6. At temperatures above the melting point of PA6, higher pressure typically resulted in higher interface strength. However, as the temperature approached the decomposition temperature, the joints under higher pressure tended to exhibit lower strength. The underlying mechanism of the interface strength variation with pressure was investigated by analyzing the effects of the joining conditions on the chemical reaction conditions, the resolidified-resin structure near the interlayer, and the existence of defects. These findings lay the foundational groundwork for future endeavors in metal/composite joining, offering potential benefits for industrial applications and environmental sustainability in the automotive sector.