Interfacial bonding mechanisms in laser welding of 2024 Al alloy and continuous CFR-PEEK via adjustable ring-mode laser beam

Abstract

Continuous carbon-fiber-reinforced polyether-ether-ketone (CFR-PEEK)/aluminum (Al) alloy heterogeneous composite joint provides a promising integration of the excellent properties of CFR-PEEK and Al alloy, and laser welding technology serves as a critical method for joining CFR-PEEK and Al alloy, offering advantages in high accuracy and efficiency. However, the inherent differences in physical and chemical properties of dissimilar materials and unclear welding mechanism limit its use in fabricating CFR-PEEK/Al alloy composite joints, and the high energy density of laser and the heat sensitivity of thermoplastic materials significantly leads to thermal risk of the joining of CFR-PEEK/Al alloy. Therefore, this work firstly established a direct joining of CFR-PEEK with Al alloy in an argon atmosphere, and further investigate interfacial bonding mechanism of various crystal planes of non-oxidized Al alloys and CFR-PEEK by interface adsorption model constructed through density functional theory (DFT) simulation, and firstly using the combined method of molecular dynamics (MD) simulation and finite element (FE) simulation to explore the interface dynamic behaviors and suitable interface temperature of CFR-PEEK and Al alloy. Furthermore, this study firstly introduced an adjustable-ring-mode (ARM) laser beam with an adjustable core/ring power ratio to optimize the heat input during welding of CFR-PEEK and high-strength 2024 Al alloy. Results indicated that PEEK could form covalent bonds with Al (111), (001), and (110) crystal planes, involving strong orbital hybridization between Al 3p and O 2p orbitals and electron transfer from Al atoms to electronegative O atoms. Furthermore, the thermal effects could be significant and precise influenced by the ARM laser beam, During the adsorption stage, the interaction energy increased most rapidly at 750 K. Guided by FE simulations, a 750 K interface temperature was selected for CFR-PEEK/2024 Al hybrid joints, and experiments demonstrated superior tensile shear strength, confirming the effectiveness of the optimized parameters and the reliability of the combined simulation-experimental approach. These findings elucidate the bonding characteristics and mechanisms of CFRTP/Al alloy joints, providing a theoretical framework for optimizing the welding process of CFR-PEEK and Al alloy.