Investigation On The Mechanical Properties Of Composite Propellant Under Medium Strain Rate Compressive Load

Solid propellant is the main energy for missiles. The solid propellant will withstand load at varied temperature and strain rate when the missiles are used, which may destroy the structural integrity of propellant, thus leads to a catastrophic accident. In order to accurately analyze the mechanical properties of propellant under high overload, the uniaxial compressive experiments of composite propellant were performed at varied temperature and strain rate. Finally, a constitutive model which can describe the mechanical properties was established.In this paper, the uniaxial compressive experiments of composite propellant were performed on universal testing machine and high strain rate testing machine at varied temperature. And the resulting stress-strain curves were obtained at strain rate between 10-4s-1 and 102s-1. Result indicates that the composite propellant is rate-sensitive material and its initial modulus at low strain rate(<1s-1)and medium strain rate(1~100s-1) are approximately linear correlation with the logarithm of strain rate. Meanwhile, the mechanical properties of composite propellant also depend on temperature: with the increase of temperature, the material becomes soft and its mechanical properties degenerate. It was found that the curve at 100s-1 appeared stress wave effect and strain rate instability obviously by analyzing the experimental curves at medium strain rate. The coefficients of ZWT constitutive model equation were obtained by genetic algorithm and this model was sufficient to characterize the mechanical properties of the composite propellant within 30% strain at strain rate between 10-4s-1 and 102s-1. The constitutive model can provide theoretical support for the rocket engine design and the propellant structural integrity. Besides, the constitutive model at high strain rate was established, but this model cannot be used for describing the mechanical properties of the composite propellant under medium strain rate load.