Optimization and microstructural study of friction riveted carbon-Kevlar and aluminum joints for aerospace applications

Friction riveting has emerged as a promising candidate for joining metals to polymers, as it is energy efficient, fast and environmentally friendly without material wastage. The joining of hybrid carbon-Kevlar polymer matrix composites with AA 7075 aluminium alloy is investigated in the current work. The multi-material joints were subjected to mechanical tests such as the T-pull tensile test and the lap shear pull-out test. The tensile load capacity and the shear pull-out capacity were 5.83 kN and 2.95 kN respectively. The process parameters involved were optimised by applying a hybrid Taguchi-Grey relation analysis. The optimum process parameters were 6000 rpm riveting speed, 0.2 MPa reaming pressure and 6 s reaming time. Optimization showed that the speed of the rivet is the most influential parameter in determining the strength of the joint and it is followed by friction time and pressure. Microstructural investigations showed the formation of different flow patterns and structures in bonding performance between carbon fibre and Kevlar fibre, that are involved in increasing the strength of the joints formed.