Enhancing the bonding reliability of titanium alloy / CFRTP hybrid joint by directionally inducing high-density covalent bond and secondary interaction via functional diblock copolymer

The hybrid joint of titanium alloy (Ti–6Al–4V)/carbon fibers reinforced thermoplastic (CFRTP) has gained high interest from the industry due to lightweight. However, the bonding reliability of fabricated joints is relatively low due to the confined mechanical interlocking and weak interfacial chemical interactions, which limits its application for engineering. Herein, the novel functional poly glycidyl methacrylate-b-poly methacryloxy propyl trimethoxyl silane (PGMA-b-PMPTS) diblock copolymers were synthesized and introduced at the contact interface of Ti–6Al–4V/carbon fibers reinforced polyether-ether-ketone joints for enhancing the bonding reliability by directional induction of chemical interactions. Fourier-transform infrared spectroscopy (FT-IR) analysis and density functional theory (DFT) simulation calculation proved that both the Si–O–Ti covalent bonds and secondary interactions were successfully induced directionally at the bonding interface. The tensile-shear strength and bending strength were thus significantly improved by 341 % to 40.17 MPa and 152 % to 238.53 MPa compared with that of 9.09 MPa and 94.53 MPa in pretreated case. The bonding reliability improved gradually with the increase of molecular weight and molecular weight ratios between functional groups of PGMA-b-PMPTS diblock copolymers. The adhesion ratio of resin-carbon fibers mixture on failure surface increased to 89.6 % after the modification with synthesized PGMA-b-PMPTS diblock copolymers, which further verified the feasibility of promoting bonding strength of Ti–6Al–4V/CFRTP by inducing the high-density interfacial interactions directionally. Current work exhibits a simple yet attractive interfacial modification strategy to achieve high-reliability hybrid joints between metal and thermoplastics.