Influence of structured surface on the interlaminar delamination properties of bonded fiber-metal laminates

Fiber-metal laminates (FMLs) often exhibit weak interlayer mechanical properties. Delamination is a common issue across FMLs and significantly affects the overall mechanical performance, highlighting the critical need to enhance the interfacial bonding between metal and resin. Structured surface treatment has emerged as a promising method to improve interfacial bonding and has garnered significant attention in adhesive bonding applications. This study investigates the impact of surface structuring on delamination properties by designing two groove patterns (circular and hexagonal) on the metal surface of carbon fiber-reinforced aluminum alloy laminates (CARALL). Specimens were prepared and subsequently subjected to mode I and mode II static delamination tests. Test results indicate that both circular and hexagonal grooves substantially enhance interlaminar fracture toughness, with hexagonal grooves showing a superior improvement. Additionally, finite element models for double cantilever beam (DCB) and end-notched flexure (ENF) tests were developed using the cohesive zone model and progressive damage method. The numerical load–displacement curves were consistent with experimental curves, confirming the accuracy and applicability of the finite element approach.