A NONLINEAR VISCOELASTIC CONSTITUTIVE MODEL FOR SOILD PROPELLANT

FAILURE ANALYSIS ASSOCIATES (FAAA) PROPOSES TO EVALUATE A NONLINEAR VISCOELASTIC CONSTITUTIVE LAW FOR MODELING THE RESPONSE OF SOLID ROCKET PROPELLANT. THIS CONSTITUTIVE LAW, WHICH IS BASED ON MODIFIED COLEMAN-NOLL MODEL, IS KNOWN AS THE BURKE MODEL, AFTER ITS DEVELOPER, DR MICHAEL A BURKE OF FAAA. THE BURKE MODEL HAS BEEN SUCCESSFULLY EMPLOYED TO ACCURATELY PREDICT THE BEHAVIOR OF POLYMERS AND RUBBER MATERIALS, BUT HAS NOT BEEN APPLIED TO PROPELLANT. IN THIS PROJECT, ALGORITHMS WILL BE DEVELOPED FOR THE BURKE MODEL AND FOR THE ANCILLARY CODE REQUIRED TO DERIVE MODEL COEFFICIENTS FROM TEST DATA. PROPELLANT BEHAVIOR PREDICTED USING THESE ALGORITHMS WILL BE COMPARED WITH EXISTING PROPELLANT TEST DATA TO PROVIDE A MEASURE OF THE ACCURACY AND APPLICABILITY OF THE BURKE MODEL. IF SUCCESS IS ACHIEVED, THE BURKE MODEL COULD THEN BE EXTENDED AND INCORPORATED INTO A FINITE ELEMENT CODE FOR USE IN THE ANALYSIS OF SOLID ROCKET MOTORS.