Assessment of Poisson's Ratio for Hydroxy-terminated Polybutadine-based Solid Rocket Propellants

  • Himanshu Shekhar High Energy Materials Research Laboratory, Pune
  • Anil D Sahasrabudhe College of Engineering, Pune
Keywords: Composite propellants, Poisson?s ratio, tensile test, incompressible materials, filled polymers, solid rocket-propellants


Poisson's ratio of hydroxy-terminated polybutadine (HTPB)-based composite propellant is estimated from uni-axial tensile testing. Double dumbbell specimens as per ASTM D638 type IV standard were used and Poisson's ratio at break, obtained by change in volume of specimen, was calculated as approximately 0.25. It was also observed that Poisson's ratio is different along different lateral directions of the propellant specimen. Poisson's ratios in two orthogonal directions perpendicular to longitudinal axis were calculated as 0.17 and 0.30. As ASTM specimen has rectangular cross-section of approximate size 6 mm x 4 mm, the directional behaviour of Poisson's ratio may be attributed to initial dimensions. Prismatic propellant specimen with square cross-section and of 115 mm x 6 mm x 6 mm dimension do not show any variation wrt Young's modulus,tensile strength, and percentage elongation as compared to ASTM specimen. Directional behaviour of Poisson's ratio with almost similar numerical value was again observed, thus ruling out dependence of this behaviour on different initial dimensions of propellant cross-section. Further, Poisson's ratio varies linearly with strain even in linear portion of stress-strain curve in uni-axial tensile testing. The rate of reduction of Poisson's ratio with increase in strain is slower in linear region and it accelerates after dewetting due to formation of vacuoles. Variation of Poisson's ratio with strain has two different slopes in linear (slope = 0.3165) and nonlinear regions (slope = 0.61364). Numerical value of slope for variation of Poisson's ratio with strain almost doubles after dewetting. It must be noted that no change in volume does not necessarily indicate constant Poisson's ratioequal to 0.5. Composite propellants behave as compressible material in most of the regions and near-failure region or at higher strains; Poisson's ratio is not anywhere near to 0.5, instead it is near 0.25.

Defence Science Journal, 2010, 60(5), pp.497-501, DOI:

Author Biographies

Himanshu Shekhar, High Energy Materials Research Laboratory, Pune
He has obtained MTech (Mech Engg) from IIT, Kanpur, and is working as Deputy Director and Head, Ballistics Group, at High Energy Materials Research Laboratory (HEMRL), Pune. He has developed infrastructure for processing large size case-bonded solid propellant rocket motors and has processed several motors, which have been fired successfully. He has designed propellant grains for various applications.


Anil D Sahasrabudhe, College of Engineering, Pune
He has obtained PhD in Mechnical Engineering from IISc, Bangaluru. Presently, he is Director and Professor (Mechanical Engineering) at the College of Engineering, Pune. He has guided 40 BTech students and 5 PhD students. He has 34 publications to his credit, organised 9 seminars and handled 9 consultancy projects.
How to Cite
Shekhar, H., & Sahasrabudhe, A. (2010). Assessment of Poisson’s Ratio for Hydroxy-terminated Polybutadine-based Solid Rocket Propellants. Defence Science Journal, 60(5), 497-501.
Research Papers