Thermoelastic modeling of high-performance carbon–carbon (C/C) brakes

Carbon–carbon (C/C) friction materials are widely used in high-performance braking systems due to their lightness, the high thermal conductivity, and low thermal expansion at high temperature. In friction brakes, the contact pressure, temperature, and sliding speed distributions are not uniform along the contact region between the disc and pads, leading to local friction coefficient variations. In this work, a literature review is conducted to investigate the complex behavior of local and global friction coefficients in braking systems, as function of their operating conditions. A multiphysics coupled thermoelastic model of a high-performance C/C braking system is presented, aimed at providing a preliminary but reliable performance assessment of new braking systems during their early design stages. Both disc and pads are modeled through the finite volume method (FVM), applied to the three-dimensional case to deal with orthotropic C/C materials. Equivalent material properties are defined through solid to void volume and surface ratios, and are assigned to the simplified geometries of disc and pads to account for the geometrical complexity of the actual components. In the paper, all mechanical and thermal balance equations governing the physics of the model are detailed. An analytical friction law is defined to compute the local friction coefficient as function of contact pressure, temperature, and sliding speed of each pair of elements in contact. The numerical results obtained show good agreement with available experimental test bench results of a reference braking system, both in terms of predicted disc surface temperature and brake torque.