Research On The Fracture Mechanics Behavior Of Modified Double Base Propellant

As the solid rocket motor develop in the direction of large caliber and long range, loading rate’s effect is more obvious with the viscoelastic material of CMDB. Especially in high ignition impact, high overload in emission, fall down and impact load et al. Its mechanical behavior is completely different from the quasi static condition, which can be described and analysed as a brittle material mechanical.In this paper, the split hopkinson bar (SHPB) and the universal material testing machine are used to study the mode I and II fracture behavior of CMDB. The tensile fracture experiment of mode I mainly carried out under the strain rate 10-4-101s-1 with uniaxial material testing machine. With the experiment we can confirm that the plane stress and the stress concentration affect the behavior of fracture, and the fracture energy changing with the strain rate under the condition of quasi-static. The fracture experiment research of mode II conducted with strain rate of 102～103s-1 under impact condition, by which the failure criterion of modified double-base propellant’s fracture under high strain rate is obtained. By contrast, shear fracture experiment at the strain rate 10-4～101s-1 is added. The experiment result of mode II fracture at high and low strain rates tell us, the modified double-base propellant shows the brittle fracture phenomenon at high strain rate and fracture occurs with large deformation under the condition of quasi-static, which means the strain rate has a great influence on the material’s fracture. The fracture energy and strain rate are linear correlation under high strain rate, and the quasi-static fracture energy is associated with strain rate exponentially.At the same time, the constitutive of modified double-base propellant was studied with split hopkinson bar, and we get the linear ZWT constitutive model that can accurately describe the material’s mechanical behavior at high strain rate. The constitutive model and fracture failure criterion expressed by VUMAT which based on FORTRAN language are used to numerical calculation. At last, the ABAQUS numerical calculation result proves the the material constitutive and fracture failure criteria are established correctly.