Damage and Dilatometry for Solid Propellants with Digital Image Correlation

Abstract

AbstractThe mechanical failure properties of composite solid propellants are determined largely by the strength of the particle matrix interfaces. Under applied loading, separation of the particulate matter from the surrounding matrix takes place, a phenomenon called dewetting. Vacuole formation and growth result in volume changes in the bulk material, so that, during tensile testing, in situ measurement of volume change correlates with this type of microstructural damage. Dewetting and dilatation have long been an important consideration, but characterization has been difficult. Fluid based dilatometry has been the dominant measurement technique but has some inadequacies. In this work, an alternative approach is shown that needs no contact with the specimen, that requires no gas or liquid, and that can accommodate various specimen geometries. Damage was induced in two common solid propellant types using either formulation considerations or strain induced damage. The volume changes during tensile testing were measured using this optical dilatometry method and show the ability of the approach to detect damage in solid propellants. Various parameters derived from the dilatation curves are compared. Verification of the approach with results from a conventional dilatometer are also included.