Aluminium and copper are two metals frequently used in the automotive and aerospace industries due to their properties of lightness and high conductivity. In this study, copper and aluminium plates were joined using the explosive welding method. The effects of the explosive ratio on the properties of the bonding interface were investigated. Results of the experimental studies showed that the bonding interface changed from a slightly wavy structure to a completely wavy structure as the explosive ratio was increased. It was found that due to the cold deformation resulting from the collision of the flyer and parent plates during the explosion, there was an increase in the hardness values near the bonding interface and on the outer surfaces of the plates. The increase in deformation hardening along with the increasing explosive ratios led to the reduced impact toughness of the composites. In the results of the tensile-shear and bending tests, no separation or fracturing was seen in the bonding interfaces at any of the explosive ratios. As a result, it was seen that the explosive welding method can be used in combining copper and aluminium materials.