The effect of surface treatments on interfacial fatigue crack initiation in aluminum/epoxy bonds

The effect of different substrate surface pre-treatments on the initiation of interfacial fatigue cracks was studied for adhesive bonds. Aluminum-epoxy bimaterial specimens were used to investigate how surface pre-treatment affects resistance to fatigue crack initiation at the interface corner. A stress singularity approach was utilized to assess the effect of four different treatments; P2 etch, phosphoric acid anodization (PAA), sulfuric acid anodization (SAA), and sol-gel. A bimaterial system with a 90° epoxy wedge was tested under sinusoidal cyclic loading. The surface treatment effect was rather significant on the resistance to fatigue crack initiation at the interface. Results show that PAA generated the strongest interface, while SAA led to the weakest for the material system studied here.