The Application of Rate Theory to the Failure of Solid Propellants
Technical Report,07 Dec 1971,30 Apr 1973
CALIFORNIA INST OF TECH PASADENA PASADENA
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The process of failure accumulation in composite propellants was studied. One part of the study was concerned with the experimental tracing of void and microcrack formation. A second part dealt with the development of a physical model of microcrack growth in which cracks grow as a function of time and load history. The law for crack growth rate was based on the fracture mechanics of fracture in viscoelastic solids. Correlation of calculations and experiments on uniaxially strained tensile specimens in single loading-unloading cycles as well as repetitive load cycling fatigue showed that the model, though relatively simple when compared with the actual physical situation, is surprisingly accurate in representing the damage accumulated under strain. Damage was directly coupled with the constitutive behavior because the growth of flaws modified the propellant rigidity. Tests on cylinders under simultaneous tension and torque indicated that the failure process in this biaxial strain state loading is nearly the same as in the uniaxial strain state.