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Opportunity at Air Force Research Laboratory (AFRL)

Understanding Explosive Behavior Through Quantified Microstructural Information

Location

Munitions Directorate, RW/Ordnance Division

RO# Location
13.45.02.C0634 Eglin Air Force Base, FL 325426810

Advisers

name email phone
Molek, Christopher David christopher.molek@us.af.mil 850-882-9244

Description

It is well established that the properties (e.g. dynamic mechanical, initiation behavior, and detonation performance) of energetic materials are influenced by the microstructural features of an explosive or propellant formulation, but the details of those dependences are poorly understood.  The detonation physics community has embraced the idea that initiation of high explosives proceeds from an ignition event through subsequent growth to steady detonation. A weakness of all the commonly used ignition and growth models is that microstructural characteristics are not explicitly incorporated in their ignition and growth terms. This is the case in spite of a demonstrated, but not well-understood, empirical link between morphology and initiation of energetic materials. Morphological effects have been parametrically studied in many ways, with the majority of efforts focused on establishing a tie between bulk explosive powder metrics and initiation of a pressed explosive sample. More recently, there has been a shift toward characterizing the microstructure of samples in order to understand the underlying mechanisms governing the initiation behavior. This work would involve characterizing microstructures using multiple techniques. This project utilizes data obtained from an atomic force microscope, scanning electron microscope, and X-Ray computed tomography. The project scope provides an opportunity to lead the establishment/development of image segmentation approaches (e.g. machine learning) for components within samples that have minimal contrast differences, establishment/development sample preparation techniques to enhancing contrast differences between components in a sample, and develop component specific quantitative data analysis techniques.  These data will be used to establish correlations between microstructural features and dynamic properties of energetic materials.  These correlations should inform us on how to maintain the balance between necessary dynamic mechanical properties requirements while maintaining adequate initiation behavior and detonation performance of the energetic material. Mentees will have the opportunity to become familiar with a wide variety of topics including; sample preparation, characterization techniques, and data analysis techniques

References:

Molek, C. D., E. J. Welle, J. O. Mares, J. Vitarelli, D. B. Hardin, and M. Stuthers. "Impact of Void Structure on Initiation Sensitivity." Propellants Explosives Pyrotechnics 45, no. 2 (Feb 2020): 236-42.

Roy, S., O. Sen, N. K. Rai, M. Moon, E. J. Welle, C. D. Molek, K. K. Choi, and H. S. Udaykumar. "Structure–Property–Performance Linkages for Heterogenous Energetic Materials through Multi-Scale Modeling." Multiscale and Multidisciplinary Modeling, Experiments and Design 3 (2020): 265-93.

Kim, S., C. Miller, Y. Horie, C. D. Molek, E. J. Welle, and M. Zhou. "Computational Predictions of Probalilstic Ignition Threshold of Pressed Granular Octahydro-1,3,5,7-Tetranitro-1,3,5,7-Tetrazocine (Hmx) under Shock Loading." J. Appl. Phys. 120 (2016): 115902.

Keywords:
Explosives; Energetic Materials; Dynamic Mechanical Properties; Shock Initiation; Detonation Performance; Microstructure; Machine Learning; AFM; SEM; XCT

Eligibility

Citizenship:  Open to U.S. citizens
Level:  Open to Postdoctoral and Senior applicants

Stipend

Base Stipend Travel Allotment Supplementation
$76,542.00 $4,000.00

$3,000 Supplement for Doctorates in Engineering & Computer Science

Experience Supplement:
Postdoctoral and Senior Associates will receive an appropriately higher stipend based on the number of years of experience past their PhD.

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