Studies on the influence of testing parameters on dynamic and transient properties of composite solid rocket propellants using a dynamic mechanical analyzer

Abstract

Dynamic mechanical analysis is a unique technique that measures the modulus and damping of materials as they are deformed under periodic stress. Propellants, which are viscoelastic in nature, are subjected to time, temperature, and frequency effects during the analysis to determine their dynamic and transient properties. The choice of parameters during the experiments like temperature, frequency, strain (%), and stress level is very crucial to the results obtained since the propellant behaves differently under different conditions. A series of experiments like strain and temperature ramp/ frequency sweeps, creep, stress relaxation, etc. have been conducted using high burning rate composite propellant (burn rate ~20 mm/s at 7,000 kPa), in order to determine the precise effects of such parameters on the results obtained. The evaluated data revealed that as the temperature increases the storage modulus, loss modulus, and tan delta curves with respect to the frequency shift towards the lower side. Moreover, there is equivalency between the increase in the temperature and the decrease in the frequency, which can be used for the time-temperature superposition principles. Further, in transient tests, the relaxation modulus has been found to decrease when increasing strain levels in the given time range. Also, relaxation modulus versus time curves were found to shift towards the lower side with increasing temperature while creep compliance decreases with the increase in stress and decrease in temperature. The glass transition value of the composite propellant increases when there is an increase in the heating rate.

Anomalous Behavior of a Solid Rocket Motor Nozzle Insert During Static Firing Test

“…According to Wani et al (2012), most composite propellants contain typically ammonium perchlorate at proportions ranging from 65 to 70% by weight, a metallic fuel like aluminum powder at proportions ranging from 15 to 20% by weight and a rubberlike binder, such as HTPB, at proportions ranging from 10 to 15% by weight. These 3 constituents can correspond approximately to the amount of 95% by weight of the propellant weight (Glotov 2006;Susuki and Chiba 1989).…”

Vibration-Induced Heating of Energetic Materials: A Review

“…Wani et al cautioned that testing parameters (heating rate, frequency, stress/strain applied, temperature etc.) affect the measured mechanical response in composite propellants [98]. They published an "exhaustive data set" using DMA testing that included multi-strain and multi-frequency strain sweeps, stress relaxation and creep tests.…”

Measuring Propellant Stress Relaxation Modulus Using Dynamic Mechanical Analyzer

“…The DMA data were used in conjunction with various analytical chemistry methods (for example, sol-gel analysis and gas permeation chromatography) to assess the aging trends in different propellants and to investigate the dominant chemical mechanisms controlling the degradation of mechanical properties. Other authors have followed similar approaches, using DMA along with analytical chemistry to determine which microstructural changes were causing propellant aging [8][9][10][11][12][13][14].…”