Thermal deformation and strength of heat-protective coatings under operating conditions simulating the real ones

The thermal deformation of a heat-protective coating of polymer composite material with a phenol-formaldehyde matrix under conditions simulating the temperature-time interval of a spacecraft deorbiting is considered. It is shown that in the plane of reinforcing of the composite the maximum thermal deformations occur in a direction at 45° to the base of the fabric of the filler and with an increase in heating rate is a significant reduction in its amplitude. The residual relative thermal deformation of the heat-protective material tested according to the program of descent from a trajectory may reach 2% and more. The calculation of thermal stresses occurring in a layer of thermal protection during a spacecraft reentry in dense atmosphere is done using a method of the theory of elasticity with allowance made for physico-mechanical characteristics obtained for conditions simulating the actual ones. The tangential stresses, τ_zθ and τ_rz, at the juncture of the frontal shield with the side surface and also at 1/5th of the length of the reentry vehicle at its both ends, at a depth of 3-3, 5 mm from the outer surface are shown to be the most dangerous for the strength of the heat-protective coating