Numerical Modelling of Composite Brake Pad Operational Deflection Shapes

Abstract

This project outlines the effect of changing Young’s modulus, Poisson’s ratios and shear modulus on the pad natural frequencies. It aims to improve the understanding of the influence of friction material properties on the pad natural frequencies, to observe how the natural frequencies can change, with the changes in the properties of the composite brake pad friction material. In addition, two different brake pad models (Pad-A and Pad-B) were designed, using CATIA V5 software to study whether different pad aspect ratios can affect the influence of friction material properties on the natural frequencies. This study utilizes the free-free analysis on the brake pads, to investigate the natural frequencies, and the mode shapes of the first four modes, using ABAQUS software. Also, an experimental test (Tap testing) on Pad-A was carried out to verify the accuracy of the numerical analysis. The research has demonstrated that the maximum variation between the numerical and the experimental results is 5.1%, which is acceptable. Thus, the numerical analysis provided reasonable results.Furthermore, the factorial analysis was applied on the obtained natural frequencies for each pad, to find out the material properties that have the main effect on the natural frequencies, and the relationship between each property and the natural frequency, using MINITAB software. The results indicated that increasing Young’s modulus in the horizontal plane can increase the values of natural frequencies, while a decrease in Young’s modulus in the vertical plane, Poisson’s ratios, and shear modulus in all planes can increase the values of the natural frequencies. Therefore, the research deduced that Young’s modulus, and Poisson’s ratios in the horizontal plane must be taken into account, when choosing a suitable orthotropic friction material for brake pads. This relationship between the friction material properties and the natural frequency is independent of pad aspect ratios, and can be concluded for all types of pads. The natural frequency plays a significant role in triggering brake squeal. Brake squeal can occur if the pad natural frequency is coupled with the disc frequency. Therefore, determining how altering friction material properties affects the pad natural frequency, can help to propose an appropriate friction material for the pad, in order to have the pad natural frequency, which is not close to the disc frequency in the frequency range, where the brake noise occurs.