Parameter Optimization and Enhancement Mechanisms of Ultrasonic Adhesive‐Impact Bonding for CNT ‐Reinforced Epoxy Adhesive Joints: A Combined Experimental and Molecular Dynamics Study

ABSTRACT This study proposed an ultrasonic adhesive‐impact bonding process tailored for carbon nanotube (CNT)‐reinforced epoxy adhesive joints. A predictive model for shear strength was established using the response surface methodology (RSM), and the optimal process parameters were determined. Under optimal conditions, the fabricated 6061 aluminum alloy/carbon fiber‐reinforced polymer (CFRP) joint exhibited a shear strength of 30.77 MPa, representing a 16.46% improvement over conventional bonding processes. The molecular dynamics (MD) simulation results indicate that ultrasonic vibration not only effectively enhances the filling behavior of adhesive molecular chains but also significantly promotes chemical reactions at the interface and within the adhesive layer. Compared with the model without ultrasonic vibration, the number of KH550 molecules participating in crosslinking increased by 57.14%, and the number of CN bonds formed increased by 63.64% under ultrasonic vibration. Meanwhile, the number of amino groups on the CNT participating in crosslinking and the associated CN bonds formed increased by 60% and 33.33%, respectively. The experimental results on interfacial microscopic morphology and chemical composition were consistent with the findings from MD simulations.