Abstract:
To evaluate the influence of the fluid-solid coupling on the mechanical properties of C/C composite material nozzle of underwater solid rocket motor, a finite element model is established for simulation analyses for cases in vacuum and underwater in different depths. It is shown that the nozzle has the highest modal frequency in vacuum; while under underwater conditions with the fluid-solid effect, the modal frequency of the nozzle reduces with the increase of the water depth due to the magnified virtual mass, and the number of coupled modes is increased. For the exciting force with a frequency in the range of 5 Hz to 800 Hz, the resonance modal rank of the nozzle increases with the fluid-solid coupling, and the maximum displacement of the vibration response of the nozzle outlet increases with the water depth. The displacement distributions of the nozzle are in a similar shape for different depths of water, with only numerical drifts; however, the stress concentration is found on the throat part of the nozzle in the case of underwater in 15 m depth, with a local stress of 2.5×10
7 Pa to 3.79×10
12 Pa, indicating a risk of destructive failure of the nozzle in the actual case.