A transient simulation of thermomechanical instability in metal-free friction materials with anisotropic properties

A two-dimensional non-linear transient thermomechanical model is developed to incorporate the anisotropic properties of a metal-free friction material sliding against a steel disc using a finite element approach. The main focus of the study is the effect of material anisotropy on thermomechanical instability (TMI) of friction linings used in automotive disc clutches or brakes. The model is validated by comparing the result to an existing eigenvalue solution. A parametric study on the material anisotropy revealed that for contact with the separation effect, an increase in elastic modulus E11 in the sliding direction and thermal conductivity K22 in the thickness direction discourage TMI formation. Conversely, a higher thermal conductivity K11 in the sliding direction and elastic modulus E22 in the thickness direction make the friction material more susceptible to TMI formation for a full-contact regime and contact with the separation effect. In addition, the effect of the thermal expansion coefficient was considered in this work.