Aging of Solid Propellants Investigated by Electromechanical Impedance Technique

Abstract

Aging induced changes in the mechanical properties of solid propellant can lead to defects, such as cracks and grain–liner separations, which limit the service lifetime of solid rocket motors. This Paper presents an active sensing in situ identification method based on the electromechanical impedance technique, which is particularly suited for monitoring aging of solid propellants. This Paper first instructs a one-dimensional viscoelastic electromechanical coupling impedance model. A relationship between the dynamic modulus of solid propellants and its mechanical impedance is established. Then numerical calculation and experimental verification of the viscoelastic impedance model are conducted. Experimental research on aging monitoring of real solid propellant rocket and thermal accelerated aging hydroxyl-terminated polybutadiene solid propellant specimens are carried out. The results show that the real part of mechanical impedance curves decreases with the increase of aging time of solid propellants, and there is an approximate exponential relationship model between the peak value of real part of mechanical impedance and thermal accelerated aging time. It can be seen that the electromechanical impedance technique is an innovative method which can effectively characterize in situ the dynamic modulus of solid propellants, monitor the aging of solid propellants, and construct the aging life prediction model.