Squeal Noise Improvement by High Damping & High Stiffness under Layer Material

The purpose of this research is to clarify how damping characteristics of Under Layer (hereafter “UL”) material in the brake pads (hereafter “PAD”) influences brake squeal noise performance. In this study, UL material structure and dynamic viscoelasticity, for two different types of UL formulations are investigated. In addition, PAD damping ratio and squeal noise performance for multiple UL formulations are verified. As a result, the raw material orientation is determined based on manufacturing method, and it causes the UL material’s anisotropic properties. Dynamic viscoelasticity are dependent on the direction in which they are measured. In particular, the loss modulus, which is the damping element of dynamic viscoelasticity, is higher in the direction of the raw material orientation for the high damping and high stiffness UL formulation. In addition, it was confirmed that this loss modulus in the direction of the raw material orientation is effective for bending vibration. In the verification, the study focuses on the PAD damping ratio and squeal noise performance in the 1st bending vibration of the PAD. It is clarified that the PAD damping ratio increased as the loss modulus increases, which leads to improve squeal noise. In conclusion, this research proves that the high damping and high stiffness UL material is effective for squeal noise improvement.