Fundamental Studies Relating to Systems Analysis of Solid Propellants, January 1, 1960-May 31, 1960

Abstract

Previous reports of this series have attempted to define some of the important parameters affecting structural integrity of solid propellant rocket grains. Three general areas have been discussed, namely material properties, analytical procedures, and criteria for mechanical failure. This particular report is devoted to failure criteria, including both limiting deformation and fracture. First of all, the characteristic material properties of filled and unfilled elastomers are described, followed by a brief description of current and proposed tests which can be conducted to obtain experimental information relating to these characteristics in such a form that they can be incorporated in structural integrity analyses. In particular, the necessity for multi-axial tests is stressed in conjunction with minor requirements for new experimental equipment. The selection of appropriate fracture criteria is discussed. Most progress, however, can be reported only in criteria for unfilled elastomers for small and large strains where it appears a distortion strain energy density may be used. It is necessary to delay any really definitive remarks upon filled elastomers or actual grain composites, and subsequent use with cumulative damage analyses, until additional experimental data for propellants is forthcoming.