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Simulation of Stress Relaxation Behaviour of Composite Propellants with Varying Solid Loading Using the Generalized Maxwell Model

Bihari Bipin Kumar, Kumaraswamy Adepu, Jain Mukesh, Kurva Ramesh, Vipin Lisha

Central European Journal of Energetic Materials

2023

Vol. 20, no. 2

221--235

Hydroxyl-terminated polybutadiene (HTPB) based composite propellants possess viscoelastic behaviour and hence time and temperature dependent mechanical properties. The mathematical analysis of viscoelastic behaviour of composite propellants becomes complex due to the non-linearity involved under various loading conditions. In the present study, a linear viscoelasticity assumption was considered to simulate stresses related to storage conditions. In this paper, a study of stress relaxation behaviour of composite propellants was carried out using the Generalized Maxwell model to obtain the material viscoelastic characteristics. The relaxation behaviour of composite propellants having solid loading varying from 85% to 89% were studied at different temperatures, from -27 to +32 °C, using a Dynamic Mechanical Analyser (DMA). The generated relaxation curves were curve fitted using MATLAB (R2022a) with the Generalized Maxwell model. The simulation demonstrated that a maximum of four elemental parameters of the Generalized Maxwell model are sufficient and can represent a best fit of the relaxation behaviour of the studied composite propellants. The equilibrium modulus was also evaluated at different temperatures, along with other material constants that are essential parameters for performing the structure integrity analysis of a solid propellant rocket motor. It was observed that the equilibrium modulus decreases with an increase in temperature, but increases with an increase in solid loading in the propellant composition formulations.

Composite Propellant Formulation of Poly (16-, 32- and 64-) Azido Dendritic Esters as Energetic Plasticizer and Evaluation of Properties

Yamajala Kanaka Durga Bhaskar, Singh Hema, Kurva Ramesh, Maurya Mehilal, Banerjee Shaibal

Central European Journal of Energetic Materials

2020

Vol. 17, no. 4

506--522

16-, 32- and 64-Polyazido hyperbranched dendrimers were synthesized from hydroxy terminated dendritic ester by following two steps namely, tosylation and azidation. The poly azido dendrimers were incorporated in composite propellant formulations as an energetic plasticizer. The physical, thermal sensitivity and ballistic properties of these composite propellants such as burning rate, Cal-val, density, ignition/decomposition temperature (AET), DSC-TGA, mechanical properties, impact and friction sensitivity were evaluated experimentally while the specific impulse (Isp) and characteristic velocity (C*) were obtained theoretically. A significant enhancement in heat release was noted in the propellant formulation having 16-azido dendritic ester as an energetic plasticizer compared to 32- and 64-azido dendritic esters and a reference composition.