Thermo-mechanical analysis of multiple particle size reinforced silicon carbide particle aluminium matrix composite brake rotor

Abstract

Braking action is recognized as one of the challenges in automotive industries as a result of frictional heat generated on the interface between brake rotor and pad. This process results to high temperature which induces several undesirable conditions such as, thermal deformation and permanent distortion resulting in braking deficiency. The application of advanced materials with improved processing technique is required to tackle these challenges for brake rotor production. In this work, multiple particle size (MPS) reinforced silicon carbide particulate (SiCp) is incorporated into aluminium matrix as reinforcement phase in order to develop a light weight automotive composite brake rotor using the novel stir casting process. Finite element (FE) and actual braking analyses were performed by considering the influence of material type, particle size variation and volume fraction on mechanical and thermal performance stability. This study covers the effect of incorporating MPS-SiC in developing aluminium matrix composite (AMC) by evaluating the microstructural and mechanical properties when compared to 6061 aluminium alloy and commercial cast iron. Actual braking test was performed using a passenger car (Proton Wira 1.3) brake system rig set up and a high speed infrared (IR) camera to capture thermal distribution on the rotor surface. It was found that the microstructural and mechanical properties of MPS-SiCp AMC were influenced by varying the 20 wt% SiC particle size in the aluminium matrix. The microstructural analysis revealed a uniform distribution of the MPS-SiC reinforced particulate in the matrix which in turn improves density and tensile strength value. The tensile strength recorded an increment of 45.8 % and 10.2 % when compared to matrix alloy and cast iron material respectively. However, the ductility reduced due to particle reinforcement. The wear rate of cast MPS-SiC AMC is lower compared to the matrix alloy and cast iron used for various type of commercial brake rotor material as revealed from previous studies. Moreover, the friction coefficient is between 0.31 to 0.44, which is observed to be within the deviation band for automotive brake system application according to the industrial standard range. On the other hand, the actual braking test for 2 MPa pressure application on the rotor contact surface revealed an average temperature of 265.1 °C and 351.6 °C for the MPS-SiC AMC and cast iron rotors respectively indicating a significant thermal difference of ~25 %. It can be therefore concluded that AMC improved heat dissipation as a result of high thermal conductivity compared to cast iron thereby avoiding undesirable effects caused at high temperature. Moreover, a good agreement was achieved for thermal profile analysis between the simulation and actual braking results which did not exceed 5.5 % for the AMC brake rotor. Conclusively, the light weight MPS-SiC AMC has successfully improved the thermal and mechanical performance of the newly fabricated AMC brake rotor.