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• Proposed a facile and eco-friendly modification method to graft CNTs onto titanium surface. • The interface between titanium and PEEK was interlinked by "coordination bridges" and CNTs network. • The interfacial shear strength between modified titanium and PEEK had an increment of 205.4 %. • The flexural strength (210.0 %), and ILSS (95.2 %) of modified CF/PEEK-Ti composites were significantly enhanced. The primary challenge of fiber metal laminates (FMLs) is the insufficient interfacial adhesion between metal and resin, which impedes the realization of the full potential. To address this issue, a two-step strategy has been proposed: firstly, via the cerium coordination-based approach, followed by grafting carbon nanotubes onto the titanium surface. This modification enhances the interfacial behavior between titanium sheets and polyetheretherketone (PEEK), resulting in increased roughness and wettability on the titanium surface, facilitating tight contact between PEEK and titanium sheets while reducing defects at the interface. Compared to CF/PEEK-sandblasted Ti, the modified CF/PEEK-Ti composites exhibit significantly enhanced interfacial shear strength, equivalent flexural strength, and interlaminate shear strength with an increase of 205.4 % (39.4 MPa), 133.3 % (1434.3 MPa) and 95.2 % (93.7 MPa), respectively. Additionally, the failure mode has shifted from interfacial failure to cohesive failure. The interface enhancement mechanism can be attributed to the synergistic effects of coordination bonding, mechanical interlocking, and multiple interactions. This facile two-step modification method demonstrates the potential to enhance the interfacial properties of CF/PEEK-Ti composites. [Display omitted] [ABSTRACT FROM AUTHOR]

The mechanical properties of carbon fiber-reinforced polymer (CFRP) composites are strongly affected by the fiber-matrix interface performance. Here, we report a mussel-inspired nondestructive method to introduce carbon nanotube (CNT) onto carbon fiber (CF) surface using polydopamine (PDA) via π-π interaction and covalent bonding. The analysis of the surface morphologies, chemical properties, and the wettability of CF reveal that the functionalized CF exhibit an increased roughness and better wettability with epoxy matrix. Mechanically, the modification improves the tensile strength of CF by 14.73%, while the interfacial shear strength and interlaminar shear strength of modified CF/epoxy composite are enhanced by 89.72% and 55.44%, respectively. The enhancement mechanism could be attributed to the interpenetrating ultra-adhesive PDA molecules and CNTs network, which provide the synergistic effects of π-π interaction, hydrogen bonding, covalent bonding, and mechanical interlocking at the interface. As a result, the applied load can be effectively transferred from resin to CFs. This study provides a convenient and environment-friendly surface treatment approach to improve the interfacial and mechanical properties of CFRP composites. [Display omitted] [ABSTRACT FROM AUTHOR]

Improving the adhesion between metal sheet and resin is an important issue for the development of high-performance fiber metal laminates (FMLs). In this study, a novel rare-earth surface modification is applied for the first time to enhance the interfacial bonding strength of titanium sheets and polyetheretherketone (PEEK). Density functional theory (DFT) calculations show that cerium element could form coordination bonds at the interfaces between metallic titanium and resin. The surface wettability of titanium sheet is boosted, which is beneficial to PEEK infiltration and physical adhesion improvement. Meanwhile, with the existence of coordination bonds at the interface, the interfacial shear strength between titanium and PEEK, and the flexural strength and interlaminar shear strength of CF/PEEK-Ti laminates are enhanced significantly. Therefore, the cerium surface modification method proposed in this study has great potentials for FMLs, which provides a new strategy for generating chemical bond at interfaces between metal and resin. [Display omitted] • Proposed a novel and facile rare-earth surface modification method. • The interface between titanium and PEEK was bonded by rare-earth coordination. • The single lap shear strength of rare-earth modified interface between titanium and PEEK had an increment of 178.0%. • The flexural strength (180.0%), and ILSS (40.0%) of rare-earth modified CF/PEEK-Ti composites were significantly enhanced. [ABSTRACT FROM AUTHOR]

Due to the inert carbon fiber (CF) surface and the poor wettability of CF with poly(ether ether ketone) (PEEK), the fiber-matrix interface bonding of CF/PEEK composite is relatively weak, which limits the mechanical performance of the composite. Herein, a complex sizing agent containing Ti 3 C 2 T x MXene, carbon nanotube (CNT), and a dual compatibilizer of polyetherimide (PEI) was fabricated to graft on the CF surface. Compared with desized CF, the modified CF/PEEK composites showed a remarkable increase in flexural strength, flexural modulus, and interlaminar shear strength of 74.16%, 63.76%, and 62.79%, respectively. The improvement could be ascribed to the synergistic effects of multiple interactions, micromechanical interlockings, and substantially improved interfacial affinity by the hybrid grafting of MXene, CNT, and PEI. We also found that the interfacial failure mechanism changes from adhesive failure to cohesive failure with such a 1D/2D coating strategy. This facile and scalable approach demonstrates its potential for effectively improving fiber-matrix interfacial properties in CF/PEEK composites. [Display omitted] •A hierarchical structure containing 2D MXene, 1D CNT, and a dual compatibilizer of PEI was constructed on the CF surface. • The tensile strength of modified CF showed an appreciable improvement of 12.02%. • The ILSS (62.79%), flexural strength (74.16%), and flexural modulus (63.76%) of modified CF/PEEK composites were significantly enhanced. [ABSTRACT FROM AUTHOR]