Correlation of the Failure Modulus to Fracture-Generated Surface Area inUniaxially Compressed M43 Gun Propellant

摘要

M43, a large-caliber, nitramine composite propellant, was tested in uniaxialcompression at a rate of 100/s to 50.0% strain at temperatures from -40 deg to 60 deg C. Similar tests were performed to 20.0 and 10.0% strain. Failure modulus values (defined below) were measured and sufficient propellant was damaged so that closed bomb firings could be performed, which determined how the grain damage affected the pressure generation at ballistic pressures. After the burning rate was established using undamaged grains, the pressure-time curves from the damaged propellant were analyzed to extract the burning surface area profiles using the analysis program BRLCB. Results showed that the intercept of the linear fitted profile on the surface area axis, which was determined by plotting surface area against the amount of the propellant charge burned and fitting the initial 10% of that curve to a least squares fit straight line, seemed to be directly related to the logarithm of the failure modulus and the end strain. The resulting three curves, one for each level of strain, fell into a series that permitted the initial effective surface area to be predicted for any combination of failure modulus and the strain level within the fracture domain. These results seem to provide a method for assessing fracture damage by means of a simple mechanical measurement.