Date of Award

Fall 2021

Document Type

Open Access Thesis

Department

Mechanical Engineering

First Advisor

Kidane Addis

Abstract

Polymer bonded explosives (PBXs), typically constitute 80-95% of energetic crystals and 5-20% of a soft polymer binder, are widely used in extreme loading conditions such as rocket propellants and explosive munitions because of their high performance and low sensitivity. The particle size of crystals has a significant effect on the mechanical properties of most polymer particulate composites.

In the study, the effect of particle size on the deformation behavior of PBX under dynamic loading is investigated. The study involves testing polymer bonded sugar (PBS) samples, a well-known mechanical simulant of PBXs, with four different crystal sizes: coarse, intermediate, fine and superfine with corresponding crystal sizes of 600-850 μm, 425-600 μm, 212-425 μm, and 100-212 μm, respectively. Dynamic compression load is applied to these samples using a split Hopkinson pressure bar (SHPB). The macroscale and local dynamic deformation of the samples are captured by taking series of images of the samples as it deforms using a high-speed camera.

From the macroscale experiment, it was observed that as the crystal size increase from superfine crystal size to coarse crystal size, the ultimate compressive stress of the PBS decreases. The mesoscale experiment shows that the local von Mises, axial and transverse strain fields of PBS for different crystal size specimens are different. The local strain fields in higher crystal size specimens such as coarse crystal size specimen are highly localized in the polymer rich regions, while more dispersed across the specimens with lower crystal size particularly superfine crystal size. The mechanism of failure for different size crystal is discussed. This study would give an in-depth knowledge and understanding of how the crystal size affects the deformation mechanics of energetic and other particulate polymer composites.

Rights

© 2021, Chizoba Onwuka

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