Abstract: A disk brake system is disclosed for a non-demountable rotary shaft, in which the brake has dismountable disks formed of thermostructural friction material, such as carbon-carbon, the aim being to confer to the resulting braking system the high resistance capacities which will enable it to withstand very high temperatures without being damaged, hence to dissipate very high energies. The disk brake finds use on a rotary shaft non-dismountable with respect to its carrying structure and is characterized in that two disks are constituted by at least two rings of thermostructural friction material, at least one of which ring is formed by at least two sectors in the same plane and assembled to the other ring by tightly fitted traversing pins, produced in the same material as the sectors. Angular connections are provided between the disks and, either the shaft, or one part of the structure.