Effect of the adhesion process and fiber orientation for low-velocity impact response of AA6061-T6 bonded with GFRP

Dissimilar material joints, such as composite materials combined with lightweight metals, have been widely used in the automobile and aerospace industries to improve fuel efficiency and reduce weight. Therefore, accurate analysis and study of the mechanical behavior of dissimilar material joints are fundamentally required. In this study, impact test analysis was performed on one-sided fiber glass composite bonded with aluminum to investigate the effect of the adhesion process and directional fiber orientation on the low-velocity impact response. Two different adhesion processes (secondary cure and co-cure) were evaluated, along with four fiber orientations (0/90°, ±15°, ±30°, and ±45°). The results demonstrated that ±30° fiber orientation exhibited the highest energy absorption, confirming its superior impact resistance. For lower fiber angles (0/90° and ±15°), secondary cure and co-cure performed similarly, with co-cure bonding showing slightly lower energy absorption. However, at higher fiber angles (±30° and ±45°), co-cure bonding significantly improved fracture resistance by reducing the fiber pullout and promoting interfacial-dominated failure modes (brooming and fiber crushing). A detailed fractographic and digital image analysis identified the different fracture zones: crack initiation, shear lips, crack propagation, final fracture, and their relations with the adhesion process and fiber orientation. © 2025 The Authors