Synergistic effect of interfacial silane film and laser texturing on joining characteristics of pretreated Al/CFRTP friction stir welded joints

• By prioritizing silane coupling before laser ablation, this hybrid pretreatment preserved precise microgroove geometry and intact silane films, thereby enabling concurrent enhancement of mechanical anchoring and chemical bonding at Al/CFRTP interfaces. • The strategy elevated tensile-shear strength to 32.6 MPa and cross-tension strength to 3.2 MPa where mechanical interlocking dominated laser-ablated zones and covalent Al-O-Si bonds combined with hydrogen bonding enhanced unablated regions. • HRTEM characterization confirmed direct atomic-scale integration of amorphous silane into nano-layered Al alloy substrates, establishing defect-free interfaces critical for dissimilar material integrity. Driven by lightweight requirements in the low-altitude economy, a synergistic laser ablation‒silane coupling process was developed to optimize friction stir welded joints between Al alloys and carbon fiber-reinforced thermoplastics (CFRTPs), with a focus on elucidating the sequence-dependent gradient interfacial joining mechanism. A sequence involving silane coupling prior to laser ablation was employed, enabling dual-mode enhancement of the interfacial geometric configuration and chemical bonding. Mechanical interlocking was ensured in laser-ablated zones, whereas the chemical bonding capacity in unablated regions was enhanced. The tensile–shear strength and cross-tension strength of the joints were measured at 32.6 MPa and 3.2 MPa, respectively. Detailed microstructural characterization revealed that mechanical interlocking occurred in the laser-ablated zones of the PA66 resin and that synergistic physicochemical reinforcement was achieved via covalent Al‒O‒Si bonds coupled with molecular chain entanglement/hydrogen bonding in unablated regions. Defect-free continuous interfacial transitions were confirmed through the penetration of nanolamellar structures by amorphous silane films. This synergistic strategy provides new insights for the high-performance joining of dissimilar metal and polymer materials.