Investigation of the effects of laser micro-texturing surface treatment and Al2O3 nano particles on the adhesion and flexural properties of GFRP/Al fiber metal laminate

Abstract

This study investigated the combined effect of laser‑induced surface microstructures (spacings of 450 μm and 900 μm, vs. untreated) and Al2O3 nanoparticles (0, 0.5, 1 wt%) in glass fiber/epoxy matrix on adhesion and flexural properties of GLARE‑type fiber metal laminates. Single-lap shear and three-point flexural tests were conducted, together with microscopic characterization of the fracture surfaces. The results showed that the highest single-lap shear strength was achieved for the specimen with a microtexture spacing of 900 μm and 1 wt% Al2O3 nanoparticles, reaching 9.8 MPa. The larger spacing reduced heat-affected zone overlap and resin flow instabilities, while improving air evacuation and resin penetration into the textured cavities, resulting in superior mechanical interlocking. Under flexural loading, the optimum performance was obtained for the specimen with a 450 μm microtexture spacing and 1 wt% nanoparticles, exhibiting a flexural strength of 393 MPa, a flexural modulus of 43.4 GPa, a flexural strain of 8.52%, and an energy absorption of 5.6 J. Compared with the untreated laminate without nanoparticles, these values represent substantial improvements in mechanical performance and damage tolerance. Microscopic observations revealed that laser texturing, combined with nanoparticle reinforcement, significantly suppressed interfacial delamination and promoted a transition from adhesive failure toward cohesive matrix-dominated fracture. Furthermore, SEM analysis showed that laser treatment generated a porous coral-like micro/nano-scale morphology that enhanced resin infiltration and provided favorable sites for nanoparticle accommodation. The combined application of laser microtexturing and Al2O3 nanoparticles produced a synergistic micro–nano reinforcement mechanism, resulting in improved interfacial adhesion and superior flexural performance.