CHARACTERIZATION OF A GLYCIDYL AZIDE POLYMER COMPOSITE PROPELLANT - STRAIN-RATE EFFECTS AND RELAXATION RESPONSE

Uniaxial tension tests were completed on a developmental GAP/PSAN soli d rocket propellant at constant strain rates ranging over three decade s and at five different temperatures. An analysis of the maximum stres s (strength) and the strain at maximum stress showed that there is a r elatively narrow range of temperatures and strain rates that give rise to strains at maximum stress that exceed 18%. The long-term equilibri um strain capability (strain endurance) appears to be between 10% and 12%. The trend of the strength and initial deformation moduli were log -linear with the reciprocal of the strain rate across three decades. H owever, the shifted master curves were log-curvilinear in form. The re lationship between the strength and the initial modulus can be approxi mated by a power law. A series of stress relaxation tests was complete d at a level of 4% strain and at five different temperatures. The init ial portion of the shifted master relaxation curve is concave-up with correspondingly high stresses and moduli. It decays with time approach ing a log-constant slope. Tensile moduli derived from constant strain rate tests were found to be consistently higher in value than the modu li as a function of time determined from relaxation tests, for an equi valent shifted time. Preliminary evidence suggests that the tensile mo dulus as a function of the reciprocal of shifted strain rate can be eq uated to the relaxation modulus as a function of shifted time through an adjustment factor. This relationship extends the relaxation modulus results back a further three and one-half decades of shifted time. (C ) 1995 John Wiley & Sons, Inc.