Correlation between adhesive film characteristics and the bonding performance

The bonding performance of carbon fiber composite joints is critically influenced by the choice of surface treatment method and adhesive film. While extensive research has focused on surface preparation, establishing the correlation between the fundamental properties of adhesive films and the bonding performance remains a significant challenge. In this study, two commercial adhesive films (Meltbond and EA7000) were systematically characterized for their physicochemical properties, surface wettability, and mechanical performance. Composite joints were subsequently fabricated using these adhesive films to bond composites treated with sanding and wet peel ply, and the bonding performance was evaluated. The results demonstrated that EA7000 exhibited higher surface energy and superior viscosity retention, whereas Meltbond showed higher tensile strength. For sanded surfaces, the high surface energy of EA7000 facilitated stronger interfacial adhesion and improved bonding quality. For surfaces treated with wet peel ply, Meltbond fully exploited its superior cohesive properties, achieving the maximum single-lap shear strength (29.26 MPa) and Mode I fracture toughness (G_IC, 871.87 J/m²). Notably, EA7000 excels through process adaptability (wetting), whereas Meltbond excels through its intrinsic energy dissipation capacity when supported by a well-prepared surface. Wet peel ply treatment increased G_IC values by 784% for Meltbond and 29% for EA7000 compared to sanding, attributed to its more uniform topography and higher surface energy. This work establishes a relationship between adhesive film and bonding performance, and provides theoretical and practical guidance for selecting optimal adhesive bonding processes for composite structures in aerospace applications.