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Determination of Optimum Length of End Release for Case Bonded Solid Propellant Rocket Motors
[Technical Report, Final Report]
ROCKETDYNE MCGREGOR TX
Pagination or Media Count:
The problem of predicting crack-type failures in composite solid rocket propellant grains has been a continuing one. The usual practice has been to use one of the classical failure theories to extrapolate the failure data collected from laboratory tests to the motor grain. Just which theory to use generally depends upon the stress state at the point being considered and the previous experience of the analyst. A new unifying approach based upon fracture mechanics is considered and evaluated both analytically and experimentally. The analytics illustrate the use of the numerical stiffness programs to compute the total strain energy in various grain-like configurations with different crack lengths and locations. The experiments were conducted to confirm the existence of a characteristic strain energy release rate for cracks propagating through propellants. Taken together, the growth of both cohesive cracks in the propellant grain and adhesive cracks along a grain-case interface can be predicted. The results reported indicate that the method may prove to be quite sensitive both for predicting the onset of grain cracking and for adjusting the design parameters to minimize the tendency for fracturing to begin.
[A, Approved For Public Release]