Fatigue characteristics of plasma treated aluminium repaired by graphite/epoxy composite patch

In the present study, the fatigue behaviour of plasma treated aluminium patched by a graphite/epoxy composite (carbon fibre reinforced plastic, CFRP) has been investigated. The aluminium was surface treated using a dc plasma containing acetylene gas and nitrogen gas at a volume ratio of 5:5 for 30 s. The effect of plasma treatment on the fatigue behaviour of the aluminium/CFRP specimen was determined from fatigue testing using two different single edge notched (SEN) specimens of cracked aluminium repaired with a CFRP patch and plasma treated aluminium also repaired with a CFRP patch. The load ratio and the frequency applied in the fatigue tests were 0.1 and 10 Hz, respectively. The surfaces of the aluminium specimens were examined using atomic force microscopy (AFM) to investigate the effect of plasma treatment on the surface morphology. The results showed that plasma treated specimens exhibited almost 12% more fatigue life than untreated specimens. The surface roughness of aluminium was increased ∼1.5 times by plasma treatment. The increased surface roughness improved the bonding strength between aluminium and the CFRP patch, increasing the fatigue life of aluminium patched by CFRP.