Effect of laser surface treatment on fracture behavior of CFRP/AL adhesive joints: An experimental investigation

Abstract

This research investigates the effect of laser surface treatment in comparison to the sanding method on the mode I fracture toughness of Al/CFRP adhesive bonding, utilizing double cantilever beam (DCB) specimens. Furthermore, the study explores the effects of nominal laser powers, scanning speeds, and hatch distances on the average roughness, morphology, and composition of the Al and CFRP surface. Analysis of scanning electron microscope (SEM) images revealed the elimination of resin and no damage to fibers. The energy dispersive spectroscopy (EDS) analysis showed a reduction in O and Si elements and an increase in C element with laser energy densities of 0.21 J/mm and 0.25 J/mm at 100 μm and 50 μm hatch distances, respectively, on the surface of CFRP. This resulted in improvement in fracture energy. Laser surface treatment of Al surface increased O element and resulted in oxidation in comparison to the sanding method and untreated surfaces, which resulted in improved adhesion of the adhesive and Al. Finally, the mode I test results indicated increased fracture energy of up to 13.55 % in favor of the laser surface treatment method through fibers tearing at CFRP fracture surface and fibers bridging.