Measurement and Simulation of the Complex Shear Modulus of Insulators

High frequency brake squeal is often suppressed by applying an insulator to the shoe plate of the pad. This may increase the damping and change the coupling conditions in a favorable way, but detailed knowledge about which of the several effects of insulators that are most important is not at hand. A joint effort is needed to increase the understanding of the effects of insulators. This paper describes a new way of measuring the shear stiffness and damping of insulators. The method can be used to measure either the individual layers in an insulator or the complete insulator that is build up of several layers.

The method does not rely on the resonant behavior of a structure and it therefore allows for measurements of the parameters over a wide frequency range. The measurement setup can be placed in a temperature chamber and this allows the parameters to be measured over a wide temperature range.

The parameters measured with this method can be used for numerical simulations with the purpose of investigating the effect of insulators in disc brakes. The measured parameters are verified by simulations of the response in a simple structure. Further measurements and simulations on brake components are included to illustrate the ability of the measured parameters to represent the properties of insulators in more complex structures.

A subsequent paper will deal with the ability of the derived insulator model to simulate the effects in a complete brake system.