Investigation on the Structural Integrity of Solid Propellant Grains with Different-Sized Void Defects

Area of Science:

• Solid Rocket Motor Technology
• Materials Science and Engineering
• Computational Mechanics

Background:

• Propellant grains in solid rocket motors are subjected to various loads during service.
• Internal pore defects can compromise the structural integrity of propellant grains.
• Understanding the mechanical response of defective propellant grains is crucial for reliable performance.

Purpose of the Study:

• To investigate the structural responses of propellant grains with internal pore defects under different loading conditions.
• To analyze the influence of pore size on stress and strain distribution.
• To provide data for the integrity evaluation and structural optimization of propellant grains.

Main Methods:

• Development of a three-dimensional finite element model for propellant-insulation layer-mold.
• Simulation of structural responses under curing cooling, curing cooling with gravity, and internal pressure loading.
• Analysis of pore defects with sizes ranging from 30 mm to 100 mm.

Main Results:

• Pores increase the overall mechanical response under curing cooling, concentrating stress at the core hole and wing groove.
• Pore size affects local stress concentration, with an 80 mm pore showing stress field interference.
• Large pores significantly reduce bearing capacity and increase propellant-mold contact pressure.
• Under combined cooling and gravity, stress concentrates at pore edges, increasing with pore size.
• Internal pressure causes stress concentration at the core hole-wing groove transition and wing groove ends.

Conclusions:

• Pore defects critically influence propellant grain structural integrity under various service loads.
• The size and location of pores dictate stress and strain patterns, impacting performance.
• Finite element analysis provides valuable insights for designing more robust propellant grains.