Crack Growth Rates in a Propellant Under Various Conditions
Abstract
Cracks may form in a solid rocket propellant during the manufacture, handling, storage, or use of the solid rocket motor. However, even after the formation of these cracks, the motor may still be usable, because the cracks may not grow under anticipated loads or may grow slowly enough to avoid catastrophic consequences before service life ends. This study attempts to answer two key questions about cracks in solid propellant: (1) at what point does a crack in propellant begin to grow, and (2) after growth begins, at what rate does this growth occur? Experimental studies at both ambient and pressurized conditions were conducted, and the results include crack growth data for different geometries at different pressures. Results show that specimen geometry and crack geometry did not significantly affect crack growth in the solid propellant. Biaxial test specimens gave similar results to single-edge notched tension (SENT) specimens, as did surface cracked specimens. This robustness did not change with the application of pressure. The effect of pressure, however, was significant, and caused a slowing of the crack growth for identical stress intensities. This slowing is due to the pressure affecting the hydrostatic component of stress near the crack tip, which in turn affects the microstructural phenomena of void nucleation, growth, and coalescence. The results show that experimenters can be less concerned with specimen geometry, but should be careful to use growth data with pressure conditions similar to those anticipated in service. (2 tables, 3 figures, 7 refs.)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 16, 2001
- Accession Number
- ADA410476
Entities
People
- Timothy C. Miller
Organizations
- Air Force Research Laboratory