Crack propagation velocity and fracture toughness of hydroxyl-terminated polybutadiene propellants with consideration of a thermo-viscoelastic constitutive model: Experimental and numerical study

Abstract

Solid rocket motors are subject to numerous temperature loads during their service life, so it is essential to investigate the sensitivity of propellant mechanical properties to temperature, particularly fracture properties. This paper presents fracture characteristics of hydroxyl-terminated polybutadiene (HTPB) propellant with mechanical-thermal coupled responses. This work investigated the fracture morphology of the HTPB propellant at different temperatures (233.15 K–333.15 K) using a self-developed thermostatic in-situ video imaging. The crack propagation velocity and J-integral were measured using single-edge notched tension (SENT) specimens. In the numerical study, a thermo-viscoelastic constitutive model combined with 1/r singular elements was used to perform calculations on J-integral. The thermo-viscoelastic constitutive model combined with a cohesive zone model was used to simulate crack propagation; meanwhile, load–displacement curves and crack propagation velocity were obtained. All simulation results were analyzed in comparison to the experimental results. The results revealed that temperature could significantly affect the fracture properties of the HTPB propellant. The fracture morphology of the HTPB propellant changed significantly at different temperatures. As the temperature decreases, the strength of the material gradually increases, with a consequent increase in the critical J-integral and a decrease in the average crack propagation velocity. The time ratio governed the regularity of average instantaneous crack propagation velocity with temperature. Furthermore, three simulation methods for calculating the J-integral were analyzed and discussed.