Study on adhesive-film bonded Al/CFRP joints strengthened by ultrasonic vibration

This study proposed a method of the adhesive-film bonded aluminum/CFRP (carbon fiber reinforced polymer composite) joints strengthened by ultrasonic vibration. An orthogonal experiment was performed to optimize ultrasonic vibration parameters, improving the bonded joints’ shear strength and stability by 29% and 33%, respectively. Static wedge tests were conducted to study the durability of the adhesive joints, showing a 63% improvement. The strengthening mechanism was analyzed in terms of microstructure and chemical bonding. With the application of ultrasonic vibration, bubbles at the bond interface burst and overflowed, reducing the weak bonding area. At the same time, the adhesive film was promoted to fill the irregular micro pits on the adherend surface, enhancing the mechanical anchoring effect between the adhesive and the adhered plate. The probability of a reaction between the cyano group in the adhesive film and the hydroxyl group on the aluminum plate’s surface was increased under the ultrasonic vibration. More carbonyl and Al-N chemical bonds were formed between the adhesive film and the aluminum plate, thus improving the bonding performance of aluminum/CFRP.