Dynamic Shearing Resistance of HTPB, Sucrose and their Polymer-Bonded Energetic Simulant

Malhotra, Pinkeesh

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Overview

Year:: 2020
Contributor:: Malhotra, Pinkeesh (creator); Guduru, Pradeep (Advisor); Clifton, Rodney (Advisor); Henann, David (Reader); Chason, Eric (Reader); Brown University. Engineering: Mechanics of Solids (sponsor)
Genre:: theses
Subject:: Experimental; Solid Mechanics; Microscopy; Thermodynamics; Equation of State; Sucrose; HTPB; High Speed Imaging; Adiabatic Shear Band; Energetic Materials; Energetic Simulants; Polymer-Bonded Explosives; Constitutive Modeling
Extent:: 29, 257 p.

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Description

Abstract:: Pressure-shear plate impact (PSPI) experiments have been performed on a polymer- bonded energetic material simulant and its constituents – a simulant crystal sucrose and an elastomeric binder HTPB. Dynamic response of each of the constituents is first investigated under a range of normal stresses (3-10 GPa) and high shear strain-rates (10^5 − 10^6 𝑠^−1). Shear strength of HTPB shows a highly pressure-dependent behavior, with the strength increasing from 120 MPa to 470 MPa as the normal stress increases nominally from 3 GPa to 9 GPa. Peak shear strength of sucrose, on the other hand, shows a relatively weak dependence on normal stress, with its shear strength increasing merely from an average value of 410 MPa to 465 MPa as the normal stress increases from 2.9 GPa to 9.5 GPa. Sucrose also exhibits pronounced strain softening under shear after reaching a peak value. A quasi-linear viscoelastic model with a pressure-dependent instantaneous elastic response is used to model HTPB. A thermodynamic framework is presented for constitutive modeling of sucrose. A finite deformation thermo- mechanical model, incorporating a complete Mie-Gruneisen equation of state, is used to model sucrose. Simulations show that the dramatic drop in shear strength of sucrose is a result of localized deformation in the form of adiabatic shear bands. PSPI experiments on the sucrose/HTPB composite show that the peak dynamic shearing resistance of the composite increases from 176 MPa to 453 MPa as the normal stress increases nominally from 3 GPa to 9.75 GPa. The shearing resistance builds up to a peak value before decreasing to a smaller non- zero value. Such a drop could be due to multiple factors like fracture of sucrose and/or HTPB, delamination of HTPB from sucrose crystals, adiabatic shear band localization in the HTPB binder or sucrose crystals and friction between fractured surfaces. Once a strong foundation for material response of constituents of a polymer- bonded simulant is laid, in-situ quantitative experimental investigation of deformation fields and mechanisms of hot-spot formation is desired. A high-speed microscopic imaging system, with a temporal resolution of 250 ns and a sub-micron spatial resolution has been built in pursuit of this goal.
Notes:: Thesis (Ph. D.)--Brown University, 2020

Content

Citation

Malhotra, Pinkeesh, "Dynamic Shearing Resistance of HTPB, Sucrose and their Polymer-Bonded Energetic Simulant" (2020). Mechanics of Solids Theses and Dissertations. Brown Digital Repository. Brown University Library. https://repository.library.brown.edu/studio/item/bdr:aktsgb3c/

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Mechanics of Solids Theses and Dissertations

Theses and Dissertations for the Mechanics of Solids department.
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