Structural design and bonding strength evaluation of Al/epoxy resin joint via interpenetrating phase layer

The effect of the volume fraction of resin (V-r) on the bonding strength of Al/epoxy resin joints via interpenetrating phase layer (IPL) was investigated. The tensile strength reached maximum to be 38.3 MPa when V-r was 85%. Fracture occurred at either epoxy resin/IPL interface or Al/IPL interface depending on V-r (V-r <= 85%; epoxy resin/IPL interface, V-r >= 85%; Al/IPL interface). Fractography revealed that the separation and the fracture of the epoxy resin occurred on the epoxy resin/IPL interface, and the separation and the fracture of Al occurred on the Al/IPL interface. These results can be explained by the strength of each interface estimated from rule of mixture. The effect of grading V-r on the bonding strength was also investigated. The tensile strength of joint with the functionally graded IPL structure was higher than that of joints with the homogenous IPL structures.