Experimental investigation of the clinching process for joining the three-layer aluminum/polymer/aluminum composite sheets

Three-layer aluminum/polymer/aluminum composite sheets are among the new materials developed to reduce the weight and fuel consumption of vehicles. Using the conventional methods for joining these materials to other materials is challenging. In this paper, the joinability of the three-layer aluminum/polymer/aluminum to a single-layer 1 mm-thickness aluminum sheet, in the clinching process is investigated. Three-layer sheets of AA5754/polyethylene/AA5754 with thicknesses of 0.5/0.6/0.5 mm were produced under laboratory conditions using two different methods; with and without a local reinforcement piece in the polymer core. The prepared specimens are joined using various geometric parameters of the clinching tools. The joint sections and their geometric parameters including interlock and neck thickness are evaluated in different joint conditions. Also, the strengths of the joints are examined by shear and peel tests. Studies show that it is possible to use the clinching process to join aluminum/polymer/aluminum sheets. Also, with a proper design of tools, the joint strength can be in the same order as the strength of the clinching of single-layer sheets. The maximum shear and peel test strengths, obtained in this study are 1288 N and 540 N, respectively. Increasing the pin penetration depth increases the interlock up to an optimal value. However, further increases in the pin penetration depth will decrease the neck thickness and joint strength. The conical angle of the pin, increasing the die cavity depth, and using a local reinforcement piece reduces the strength of the clinched joint and interlock in these materials. In all the test conditions, the most suitable joint conditions were when the failure mode was combined bottom separation and neck fracture mode.