Visco-elastic-plastic Yield Model of NEPE Propellant Considering Aging at Low and Medium Strain Rates

In the first part of this study, uniaxial tensile tests were conducted on nitroester-plasticized polyether (NEPE) propellant before and after aging to analyze its yield and damage characteristics at low to moderate strain rates (1.190×10 -4 s -1 ~ 2.381 s -1 ). Electron microscopy tests were performed to compare the damage mechanisms at low to moderate strain rates before and after aging. The test curve reveals that the "dewetting point" strain of the propellant exhibits excellent strain rate insensitivity. Based on this, this study establishes the "dewetting" stress as the criterion for material yield strength. A visco-elastic-plastic yield model for NEPE propellant, accounting for aging, is constructed. Relationships between dynamic yield strength, viscoplastic strain rate, and static yield strength are produced by adding an aging factor and a dynamic yield function. Results indicate that as the propellant ages, the failure mode shifts from matrix failure to interfacial failure and particle dewetting. The yield model yields a static yield strength of 0.2483 MPa for NEPE propellant, significantly below the design strength.