Title:
Intermediate Strain Rate Behavior of Two Structural Energetic Materials

dc.contributor.advisor Zhou, Min
dc.contributor.author Patel, Nitin R. en_US
dc.contributor.committeeMember McDowell, David
dc.contributor.committeeMember Thadhani, Naresh
dc.contributor.department Mechanical Engineering en_US
dc.date.accessioned 2005-03-01T19:35:33Z
dc.date.available 2005-03-01T19:35:33Z
dc.date.issued 2004-12-08 en_US
dc.description.abstract A new class of materials, known as multi-functional energetic structural materials (MESMs), has been developed. These materials possess both strength and energetic functionalities, serving as candidates for many exciting applications. One of such applications is ballistic missiles, where these materials serve as part of structural casing as well as explosive payload. In this study, the dynamic compressive behavior of two types of MESMs in the intermediate strain rate regime is investigated. The first type is a thermite mixture of Al and Fe₂O₃ particles suspended in an epoxy matrix. The second type is a shock compacted mixture of Ni and Al powders. Compression experiments on a split-Hopkinson pressure bar (SHPB) apparatus are carried out at strain rates on the order of 103 s-1. In addition, a novel method for investigating the dynamic hardness of the Al + Fe₂O₃ + Epoxy materials is developed. In this method, high-speed digital photography is used to obtain time-resolved measurements of the indentation diameter throughout the indentation process. Experiments show that the shock compacted Ni-Al material exhibits a rather ductile behavior and the deformation of the Al + Fe₂O₃ + Epoxy mixtures is dominated by the polymer phase and significantly modulated by the powder phases. The pure epoxy is ductile with elastic-plastic hardening, softening, and perfectly plastic stages of deformation. The Al and Fe₂O₃ particles in Al + Fe₂O₃ + Epoxy mixtures act as reinforcements for the polymer matrix, impeding the deformation of the polymer chains, alleviating the strain softening of the glassy polymer matrix at lower levels of powder contents (21.6 - 29.2% by volume), and imparting the attributes of strain hardening to the mixtures at higher levels of powder contents (21.6 - 49.1% by volume). Both the dynamic and quasi-static hardness values of the Al + Fe₂O₃ + Epoxy mixtures increase with powder content, consistent with the trend seen in the stress-strain curves. To quantify the constitutive behavior of the 100% epoxy and the Al + Fe₂O₃ + Epoxy materials, the experimentally obtained stress-strain curves are fitted to the Hasan-Boyce model. This model uses a distribution of activation energies to characterize the energy barrier for the initiation of localized shear transformations of long chain polymeric molecules. The results show that an increase in powder content increases the activation energy, decreases the number of transformation sites, causes redistribution of applied strain energy, and enhances the storage of inelastic work. These effects lead to enhanced strength and strain hardening rate at higher levels of powder content. en_US
dc.description.degree M.S. en_US
dc.format.extent 4662355 bytes
dc.format.mimetype application/pdf
dc.identifier.uri http://hdl.handle.net/1853/4865
dc.language.iso en_US
dc.publisher Georgia Institute of Technology en_US
dc.subject Fe₂O₃ en_US
dc.subject Al
dc.subject Epoxy
dc.subject Hopkinson bar
dc.subject Intermediate strain rate behavior
dc.subject Energetic materials
dc.subject Epon
dc.subject.lcsh Metal powders Compression testing en_US
dc.subject.lcsh Ballistic missiles en_US
dc.subject.lcsh Materials Compression testing en_US
dc.title Intermediate Strain Rate Behavior of Two Structural Energetic Materials en_US
dc.type Text
dc.type.genre Thesis
dspace.entity.type Publication
local.contributor.advisor Zhou, Min
local.contributor.corporatename George W. Woodruff School of Mechanical Engineering
local.contributor.corporatename College of Engineering
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relation.isOrgUnitOfPublication c01ff908-c25f-439b-bf10-a074ed886bb7
relation.isOrgUnitOfPublication 7c022d60-21d5-497c-b552-95e489a06569
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