A study on the peel and shear strength of aluminum/CFRP composites surface-treated by plasma and ion assisted reaction method

This study investigates the effect of surface treatment of aluminum and CFRP on the peel strength and the shear strength of aluminum/CFRP composites. The surface of the aluminum was treated using DC plasma and the surface of the CFRP was treated by Ar+ IAR (ion assisted reaction) method under oxygen environment. Optimal plasma treatment conditions (treatment time, ratio of acetylene gas to nitrogen gas) and the optimal Ar+ ion dose were determined. In order to determine the treatment effect on the peel strength and the shear strength of aluminum/CFRP composites, T-peel tests and SLS (single lap shear) tests were performed using four types of specimens: (1) plasma-treated aluminum/irradiated CFRP specimen, (2) plasma-treated aluminum/untreated CFRP specimen, (3) untreated aluminum/ irradiated CFRP specimen, (4) untreated aluminum/untreated CFRP specimen. The results showed that the optimal plasma treatment time and the ratio of acetylene gas to nitrogen gas were 30sec and 5:5, respectively. The optimal Ar+ dose of CFRP was in a range of 10^15–10^16 ions/cm^2. The results also showed that the bond strength (T-peel strength and shear strength) of plasma-treated aluminum/irradiated CFRP specimen was largest and that of untreated aluminum/untreated CFRP specimen was smallest. The untreated aluminum/irradiated CFRP specimen produced better bond strength than the plasma-treated aluminum/untreated CFRP specimen. It was found from SEM examination that cohesive failure of epoxy adhesive occurred for specimens surfacetreated by plasma or ion irradiation while adhesive failure occurred for untreated specimens.