Critical conditions for fracture of burning stressed-strained composite solid propellants

Fracture of burning stressed-strained composite solid propellants (CSP) is studied as applied to the conditions of burning of a propellant charge rigidly fixed in the combustion chamber of a rocket motor. An experimental technique enabling fracture of burning CSP charges subject to high-rate stretching under conditions of hydraulic compression to be studied is developed. The critical conditions for fracture of burning stressed-strained CSP in the form of a growing main crack are ascertained. The conditions can be specified as follows: (i) for samples with a deliberately cut crack this is a critical strain and (ii) for samples with no precut cracks, durability. The effect of physical and mechanical propellant properties, strain rate, and pressure in the combustion chamber on the criteria is explored. The role played by the burning process enhancing the growth of microscopic cracks at an early stage of the fracture process is considered.