Micro and nano composites composed of a polymer matrix and a metal disperse phase.

Micro and nano composites composed of a polymer matrix and a metal disperse phase.

Date: December 2007
Creator: Olea Mejia, Oscar Fernando
Description: Low density polyethylene (LDPE) and Hytrel (a thermoplastic elastomer) were used as polymeric matrices in polymer + metal composites. The concentration of micrometric (Al, Ag and Ni) as well as nanometric particles (Al and Ag) was varied from 0 to 10 %. Composites were prepared by blending followed by injection molding. The resulting samples were analyzed by scanning electron microscopy (SEM) and focused ion beam (FIB) in order to determine their microstructure. Certain mechanical properties of the composites were also determined. Static and dynamic friction was measured. The scratch resistance of the specimens was determined. A study of the wear mechanisms in the samples was performed. The Al micro- and nanoparticles as well as Ni microparticles are well dispersed throughout the material while Ag micro and nanoparticles tend to form agglomerates. Generally the presence of microcomposites affects negatively the mechanical properties. For the nanoparticles, composites with a higher elastic modulus than that of the neat materials are achievable. For both micro- and nanocomposites it is feasible to lower the friction values with respective to the neat polymers. The addition of metal particles to polymers also improves the scratch resistance of the composites, particularly so for microcomposites. The inclusion of Ag ...
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Aliens and atheists: The Plurality of Worlds and Natural Theology in Seventeenth-Century England.

Aliens and atheists: The Plurality of Worlds and Natural Theology in Seventeenth-Century England.

Date: December 2007
Creator: Oliver, Ryan
Description: The plurality of worlds has had a long history in England, which has not gone unnoticed by scholars. Historians have tended to view this English pluralist tradition as similar to those found on the continent, and in doing so have failed to fully understand the religious significance that the plurality of worlds had on English thought and society. This religious significance is discovered through a thorough investigation of plurality as presented by English natural philosophers and theologians, and in so doing reveals much about England in the seventeenth century. As natural philosophers incorporated plurality within the larger framework of natural theology, it became a weapon of science and reason to be used against the unreasonable atheists of late seventeenth-century England.
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Microstructural evolution in elastically stressed systems. Final report

Microstructural evolution in elastically stressed systems. Final report

Date: September 14, 1997
Creator: Johnson, W.C.
Description: The results, which have been compared to numerical simulations and found to be in very good agreement, predict that diviations in composition on the order of several atomic percent (measured with respect to equilibrium compositions) are possible at the interface. Interfacial compositions are strongly time dependent and are also influenced by the stress state.
Contributing Partner: UNT Libraries Government Documents Department
Subcritical Crack Growth in Ceramic Composites at High Temperature Measured Using Digital Image Correlation

Subcritical Crack Growth in Ceramic Composites at High Temperature Measured Using Digital Image Correlation

Date: January 11, 1996
Creator: Mumm, D.R.; Morris, W.L.; Dadkhah, M.S. & Cox, B.N.
Description: An in situ experimental technique is described that allows high resolution, high sensitivity determination of displacements and full-field strains during high temperature mechanical testing. The technique is used to investigate elevated temperature crack growth in SiC/Nicalon sub f composites. At 1150 degrees C, the reinforcing fibers have a higher creep susceptibility than the matrix. Fiber creep leads to relaxation of crack bridging tractions, resulting in subcritical crack growth. Differential image analysis is used to measure the crack opening displacement profile u(x) of an advancing, bridged crack. With appropriate modeling, such data can be used to determine the traction law, from which the mechanics of cracking and failure may be determined.
Contributing Partner: UNT Libraries Government Documents Department
Fiber-Matrix Interface Studies on Electron Beam Cured Composites

Fiber-Matrix Interface Studies on Electron Beam Cured Composites

Date: May 23, 1999
Creator: Drazel, L.T.; Janke, C.J. & Yarborough, K.D.
Description: The recently completed Department of Energy (DOE) and industry sponsored Cooperative Research and Development Agreement (CRADA) entitled, ''Electron Beam Curing of Polymer Matrix Composites,'' determined that the interlaminar shear strength properties of the best electron beam cured IM7/epoxy composites were 19-28% lower than autoclave cured IM7/epoxy composites (i.e. IM7/977-2 and IM7/977-3). Low interlaminar shear strength is widely acknowledged as the key barrier to the successful acceptance and implementation of electron beam cured composites in the aircraft/aerospace industry. The objective of this work was to improve the interlaminar shear strength properties of electron beam cured composites by formulating and evaluating several different fiber sizings or coating materials. The researchers have recently achieved some promising results by having discovered that the application of epoxy-based, electron beam compatible sizings or coatings onto surface-treated, unsized IM7 carbon fibers improved the composite interlaminar shear strength properties by as much as 55% versus composites fabricated from surface-treated, unsized IM7 fibers. In addition, by applying these same epoxy-based sizings or coatings onto surface-treated, unsized IM7 fibers it was possible to achieve an 11% increase in the composite interlaminar shear strength compared to composites made from surface-treated, GP-sized IM7 fibers. Work is continuing in this area of research ...
Contributing Partner: UNT Libraries Government Documents Department