Show simple item record

dc.contributor.advisorThadhani, Naresh N.
dc.contributor.authorBreidenich, Jennifer L.
dc.date.accessioned2016-01-07T17:36:02Z
dc.date.available2016-01-07T17:36:02Z
dc.date.created2015-12
dc.date.issued2015-11-11
dc.date.submittedDecember 2015
dc.identifier.urihttp://hdl.handle.net/1853/54403
dc.description.abstractThis work focuses on understanding the impact-initiated combustion of aluminum powder compacts. Aluminum is typically one of the components of intermetallic-forming structural energetic materials (SEMs), which have the desirable combination of rapid release of thermal energy and high yield strength. Aluminum powders of various sizes and different levels of mechanical pre-activation are investigated to determine their reactivity under uniaxial stress rod-on-anvil impact conditions, using a 7.62 mm gas gun. The compacts reveal light emission due to combustion upon impact at velocities greater than 170 m/s. Particle size and mechanical pre-activation influence the initiation of aluminum combustion reaction through particle-level processes such as localized friction, strain, and heating, as well as continuum-scale effects controlling the amount of energy required for compaction and deformation of the powder compact during uniaxial stress loading. Compacts composed of larger diameter aluminum particles (~70µm) are more sensitive to impact initiated combustion than those composed of smaller diameter particles. Additionally, mechanical pre-activation by high energy ball milling (HEBM) increases the propensity for reaction initiation. Direct imaging using high-speed framing and IR cameras reveals light emission and temperature rise during the compaction and deformation processes. Correlations of these images to meso-scale CTH simulations reveal that initiation of combustion reactions in aluminum powder compacts is closely tied to mesoscale processes, such as particle-particle interactions, pore collapse, and particle-level deformation. These particle level processes cannot be measured directly because traditional pressure and velocity sensors provide spatially averaged responses. In order to address this issue, quantum dots (QDs) are investigated as possible meso-scale pressure sensors for probing the shock response of heterogeneous materials directly. Impact experiments were conducted on a QD-polymer film using a laser driven flyer setup at the University of Illinois Urbana-Champaign (UIUC). Time-resolved spectroscopy was used to monitor the energy shift and intensity loss as a function of pressure over nanosecond time scales. Shock compression of a QD-PVA film results in an upward shift in energy (or a blueshift in the emission spectra) and a decrease in emission intensity. The magnitude of the shift in energy and the drop in intensity are a function of the shock pressure and can be used to track the particle scale differences in the shock pressure. The encouraging results illustrate the possible use of quantum dots as mesoscale diagnostics to probe the mechanisms involved in the impact initiation of combustion or intermetallic reactions.
dc.format.mimetypeapplication/pdf
dc.language.isoen_US
dc.publisherGeorgia Institute of Technology
dc.subjectIR
dc.subjectCTH
dc.subjectHEBM
dc.subjectCdTe
dc.subjectCombustion
dc.subjectAluminum
dc.subjectExplosives
dc.subjectCompact
dc.subjectReaction
dc.subjectHigh strain rate behavior
dc.subjectStructural energetic materials
dc.subjectIntermetallic forming mixtures
dc.subjectRod-on-anvil
dc.subjectPowder
dc.subjectMechanical pre-activation
dc.subjectHigh energy ball milling
dc.subjectSpectroscopy
dc.subjectGas gun
dc.subjectPressure
dc.subjectLight emission
dc.subjectMicrostructure-based simulations
dc.subjectParticle-particle interactions
dc.subjectParticle-level process
dc.subjectCompaction
dc.subjectDeformation
dc.subjectImpact
dc.subjectQuantum dots
dc.subjectLaser-accelerated flyer
dc.subjectShock compression
dc.subjectBlueshift
dc.subjectMesoscale diagnostic
dc.subjectHeterogeneous materials
dc.titleImpact-initiated combustion of aluminum
dc.typeDissertation
dc.description.degreePh.D.
dc.contributor.departmentMaterials Science and Engineering
thesis.degree.levelDoctoral
dc.contributor.committeeMemberSanders, Thomas H.
dc.contributor.committeeMemberGokhale, Arun M.
dc.contributor.committeeMemberDwivedi, Sunil
dc.contributor.committeeMemberPeiris, Suhithi
dc.date.updated2016-01-07T17:36:02Z


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record