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Full-Text Articles in Engineering Science and Materials

Multiscale Modeling And Simulation Of Nanocrystalline Zirconium Oxide, Chaojun Wang Dec 2009

Multiscale Modeling And Simulation Of Nanocrystalline Zirconium Oxide, Chaojun Wang

Engineering Mechanics Dissertations & Theses

Nanocrystalline zirconium oxide (ZrO2) nanofibers fabricated with the sol-gel electrospinning process are expected to provide a new class of super-strong yet ultra-flexible materials. To predict their mechanical properties, we have carried out multiscale modeling and analyses. A computational model that combines the Voronoi polycrystal simulation of nanocrystalline structure with the finite element analysis has been developed. It enables the use of the first-principles predictions for the three ZrO2 crystal phases in continuum analysis of the elastic stress and strain fields in the nanofibers under uniaxial-stress tension. Calculations have been performed for each of the three phases and for ...


The Effects Of Combined Compression And Aging On The Properties Of Glassy Polycarbonate, Kyle W. Strabala Aug 2009

The Effects Of Combined Compression And Aging On The Properties Of Glassy Polycarbonate, Kyle W. Strabala

Engineering Mechanics Dissertations & Theses

Physical aging and plastic flow are known to cause changes in the properties of glassy polycarbonate (PC). Although the individual effects of physical aging and plastic flow have been studied, the combined mechanical and thermal effects have yet to be evaluated for PC at large plastic strains. This work is the first characterization of the combined effects in PC of large plastic flow followed by thermal (physical) aging. To conduct this study, samples were prepared with different extents of plastic compressive strain, up to approximately 50% engineering strain, followed by thermal aging up to 135 °C, with various aging times ...


Multiscale Modeling Of Glass Fiber Reinforced Viscoelastic Polymers Subjected To Impact Loads, Victor Ferreira Teixeira Jun 2009

Multiscale Modeling Of Glass Fiber Reinforced Viscoelastic Polymers Subjected To Impact Loads, Victor Ferreira Teixeira

Engineering Mechanics Dissertations & Theses

New applications for polymer composite materials are occurring at a rapid pace today. These include structural components in the energy, transportation, and biomedical fields. Many if not all of these new applications will require that part performance is insured with some degree of sustainable damage. With the growth in the use of composite structures comes the necessity of improved methodologies that can predict more accurately the life and serviceability conditions of composite parts. Damage mechanics in two-phase composite materials is a very complex problem that has challenged researchers for many years. However, most of the available models perform only a ...


Multiscale Modeling Of Impact On Heterogeneous Viscoelastic Solids With Evolving Microcracks, Flavio V. Souza Apr 2009

Multiscale Modeling Of Impact On Heterogeneous Viscoelastic Solids With Evolving Microcracks, Flavio V. Souza

Engineering Mechanics Dissertations & Theses

Multiscale computational techniques play a major role in solving problems related to viscoelastic composite materials due to the complexities inherent to these materials. In the present work, a numerical procedure for multiscale modeling of impact on heterogeneous viscoelastic solids containing evolving microcracks is proposed in which the (global scale) homogenized viscoelastic incremental constitutive equations have the same form as the local scale viscoelastic incremental constitutive equations, but the homogenized tangent constitutive tensor and the homogenized incremental history dependent stress tensor depend on the amount of damage accumulated at the local scale. Furthermore, the developed technique allows the computation of the ...