Influence of Tool Rotational Speed on the Mechanical Properties of Friction Stir Spot Welded AA5052-H32/PU Foam/AA5052-H32 Sandwich Sheets

Depending on the core material, the sandwich structures are seen as alternative to several functional materials including honeycomb structures (Crupi et al. in Mar Struct 74–96, 2012). The sandwich sheets have wide range of applications as vibration and sound isolators in automobile, marine, rapid transport system, and in constructions as prefabricated products/building panels, etc. (Vijaya Ramnath et al. Mater Today: Proceed 16:859–864, 2019). The current article presents the results of investigation on fabrication of PU foam core AA5052-H32 face sheet sandwich structure by friction stir spot welding (FSSW). The polymer core sandwiches are traditionally made by adhesive bonding which has typical limitations associated with stiffness and brittleness. In this context, in the current work, AA5052-H32 face sheet of 2 mm thickness and PU foam core of 20 mm thickness were FSSW from both sides by using pinless tool. Tool rotational speed was varied systematically at five levels from 710 to 1800 rpm using a specially designed fixture. The effect of tool rotational speed with and without holes on skin sheet on the bonding strength of the sandwich sheet structure is reported. The preliminary investigation suggests intimate interlocking between the AA5052-H32 face sheet and PU foam. An increase in the rotational speed resulted in a significant change in lap shear strength of the sandwich structure. It is observed that the interfacial joint strength of the FSSW sandwich sheet structure is comparable to that of PU foam core. The sandwich sheets fabricated by FSSW performs better than adhesive bonded sheets in terms lap shear fracture load.