Long-term stability analysis and failure mode of composite solid propellant: Experiment and modeling

Abstract

Composite solid propellant will inevitably experience long-term loading environments in aerospace structures and weaponry applications. However, failure modes such as delayed fracture and wire drawing under far lower service loading conditions restrict propellant applicability. Here, we proposed methods for analysing long-term stability and failure prediction. Relaxation and creep tests were carried out to discuss the stress sensitivity, stress softening characteristics, and failure modes of propellant. Based on irreversible thermodynamic internal state variable (ISV) theory, evolution equations for the conjugate thermodynamic forces of viscoelasticity, viscoplasticity, and damage ISVs are determined, and the viscoelastic-viscoplastic constitutive model with damage is developed. The long-term stability of propellant during creep and relaxation is discussed by using Lyapunov’s direct method with intrinsic dissipation rate as the Lyapunov function. The results show that the proposed methods successfully predict failure modes of wire drawing and delayed fracture under long-term load conditions, and reveal its thermodynamic mechanism. This work presents new theoretical and experimental guidelines for long-term stability analysis of propellant and other particle reinforced materials.