A Comparative Study on the Bond Strength and Failure Mechanisms of CFRP / AA7075 ‐ T6 Joints: Effects of Sandblasting and Anodizing Process

ABSTRACT This study investigates the bonding performance of carbon fiber reinforced polymer (CFRP) and AA7075‐T6 aluminum alloy hybrid structures, which are critical for aerospace and defense applications. The research evaluates the impact of various metal surface treatments on adhesion using a Syensqo MTA 240 epoxy‐based adhesive film. Five distinct surface configurations were applied to the AA7075‐T6 plates: HNO ₃ etching, NC machined cross‐hatching, silica grit blasting, and clear anodizing following glass bead blasting. These treatments yielded surface roughness values ranging from Ra 0.23 to 4.10 μm. Single‐lap shear tests were conducted according to ASTM D1002, and failure mechanisms were characterized using optical microscopy, SEM, and X‐Ray Fluorescence (XRF) analyses. The results revealed that anodized and silica‐sandblasted specimens achieved 98% and 82% higher lap shear strength than the untreated reference specimen, respectively. Conversely, cross‐hatched specimens exhibited the lowest performance at 7.30 MPa. Metallographic investigations and SEM‐XRF analyses demonstrated that both the cross‐hatch patterns and the as‐received surfaces had a detrimental effect on the bonding performance. In contrast, it was determined that sandblasting and anodizing treatments facilitated the joining of AA7075‐T6 and CFRP plates, resulting in a stronger interfacial bond.