Effect of Brake Insulator Bond State on Damping Performance 2010-01-1700

Meeting specific bonded insulator attachment specifications depend on the type of bonding polymer selected as well as application conditions. These conditions include initial apply parameters (time, temperature and pressure), backing plate surface characteristics (surface material, flatness, finish) and strength properties that avoid cohesive, adhesive or mixed mode failures during operating life of the braking pad assembly. “T-pull” and “Lap Sheaf testing provide an overall quantitative method to determine tensile and shear load/deflection properties. They do not assess the three dimensional dynamic stress state of the bond during braking conditions which involve the influence of temperature, apply pressure, rotational inertial forces and cyclic frequency/strain rate effect.

The operational factors which change the state of bond have an effect on damping performance and ability to control overall system noise. Bonding polymers are not linear isotropic materials and are quite sensitive to these factors. The equilibrium condition at the adhesive interfaces (insulator and backing plate planes) as well as within the internal cohesive region have loss and storage modulus properties which are highly dependent to variation of the operational factors. This visco-elastic behavior of the bond introduces a physical state of uncertainty which is undetermined in both strength and damping based energy dissipation. Existing bench test methods provide some comparative results in measuring performance. The dependent effects between bond and dynamic control rely primarily on dynamometer iterative trials. This study reviews several investigations conducted in determining the influence of bond state on insulator dynamic properties with conclusions on what the effects are as well as approaches to improve the quantitative relationship between bond state and dynamic properties.