As in the previous progress reports, the contents in this report have been categorized so as to present a clear picture of their role in contributing to the problem of mechanical failure analysis. The subject of material representation by mechanical failure analysis. The subject of material representation by mechanical models is discussed in Section I, while Section II contains additions to the subject of Elastic Solutions for cylinders. The Engineering Analysis section includes an example of the strain response of an internal star grain to pressure. A damped sinusoid has been assumed for the pressure rise, and the use of stress concentration factors for a star grain is demonstrated. Section V on failure includes some preliminary test results which indicate the feasibility of the cumulative damage concept for composite (polyurethane) propellants, at least in the limited range tested. Recommendations are given which would expand this testing to show how damage accumulates under other conditions such as low temperatures, high strain-rates and with other types of propellant
