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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The high-temperature, alkaline degradation of a new cellulose model compound

Kaylor, Rosann Matthews 05 1900 (has links)
No description available.
2

Fatigue delamination growth under cyclic compression in unidirectional composites

Malik, Basharat U. 12 1900 (has links)
No description available.
3

Nonlinear aeroelastic effects in damaged composite aileron-wing structures

Douxchamps, Benoit 12 1900 (has links)
No description available.
4

Reactive molding and self-assembly techniques for controlling the interface and dispersion of the particulate phase in nanocomposites.

Pranger, Lawrence A.. January 2008 (has links)
Thesis (Ph.D)--Materials Science and Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Tannenbaum, Rina; Committee Member: Garmestani, Hamid; Committee Member: Jacob, Karl; Committee Member: Patterson, Tim; Committee Member: Singh, Preet. Part of the SMARTech Electronic Thesis and Dissertation Collection.
5

Crack branching in cross-ply composites

La Saponara, Valeria 05 1900 (has links)
No description available.
6

Transport of seawater and its influence on the transverse tensile strength of unidirectional composite materials

Unknown Date (has links)
The objective of this research was to characterize the seawater transport and its effect on the transverse tensile strength of a carbon/vinylester composite. The moisture contents of neat vinylester and unidirectional carbon/vinylester composite panels immersed in seawater were monitored until saturation. A model for moisture up-take was developed based on superposition of Fickian diffusion, and Darcy’s law for capillary transport of water. Both the predicted and measured saturation times increased with increasing panel size, however the diffusion model predicts much longer times while the capillary model predicts shorter time than observed experimentally. It was also found that the saturation moisture content decreased with increasing panel size. Testing of macroscopic and miniature composite transverse tensile specimens, and SEM failure inspection revealed more fiber/matrix debonding in the seawater saturated composite than the dry composite, consistent with a slightly reduced transverse tensile strength. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection
7

Environmental life cycle driven decision making in product design

Lu, Di 02 June 2010 (has links)
There is growing interest in the assessment of products from a life cycle perspective. Product life cycles are often dominated by extensive chemical supply chains that lead up to the materials contained in the products and the overwhelming contribution that the production of these chemicals make to the overall life cycle due to their energy intensity. Hence, chemical engineers are uniquely positioned to carry out significant components of this assessment because of their skills in chemical process design and analysis. Furthermore, the complexity and extent of life cycle concerns creates opportunities for new process systems tools to be developed to support product design and analysis. The specific thesis objectives are threefold. The first is to develop a systematic methodology to optimize material selections for a product based on life cycle inventory (LCI) characteristics. The second is to use this methodology combined with sustainability assessment standards to assess whether these standards are congruent with life cycle assessment. The third is to develop an approach to design product sustainability assessment standards that are clear and consistent with life cycle principles. The overall contributions will be in the applied domain of life cycle assessment and its integration into standards setting, and in contributions to optimization tools and methods. The three objectives will be illustrated in the domain of carpet systems. Previous research has generated a substantial database of gate-to-gate (GTG) life cycle inventories for various chemicals that make up carpet, extending from the inputs to the final carpet mill back to the natural resources such as oil, natural gas and mined calcium carbonate. Carpet recycling is a promising alternative approach for reducing life cycle impacts and is being practiced at a growing scale in the U.S. This thesis uses the specific individual LCI gate-to-gate blocks for virgin materials and for important carpet recycling and general polymer recycling processes. A database for the GTG LCI will be used to construct a virtual chemical tree that automatically that represents the potential cradle-to-gate (CTG) use of resources. The alternatives for each possible route for the product will be generated, and optimization approaches will be applied to optimize the performance of the carpet system according to life cycle objectives. Sustainability assessment standards are currently being developed for a range of building products, such as carpet, resilient flooring, commercial textile coverings and office furniture. This activity has been stimulated through the considerable success of the U.S. Green Building Council's (USGBC) LEED standard. The LEED Standard is points-based: the building design and construction earns points for having certain attributes or promoting certain activities. The points are totaled and then the building earns a rating based on the total being above a certain threshold. The second thesis objective is met through extending the LCI optimization methodology to represent point-based standards. A product can then be optimized to maximize the number of points it earns or to minimize its life cycle attributes. This approach can be used to evaluate the effectiveness of an emerging carpet sustainability standard, NSF-140, in integrating LCI into the standard. The last objective, standard design, is approached through designing the tables that award points in the standard to be consistent with life cycle information. Certain minimum principles of consistency are articulated and then the designs shown to be consistent with these principles in the case that the life cycle impact assessment method maps the life cycle inventory to impact through a linear weighting.
8

Reactive molding and self-assembly techniques for controlling the interface and dispersion of the particulate phase in nanocomposites.

Pranger, Lawrence A. 07 November 2008 (has links)
This research explored the processing and properties of PNCs using a polyfurfural alcohol (PFA) matrix. The precursor for PFA, furfuryl alcohol (FA) is sourced from feedstocks rich in hemicellulose, such as corn cobs, oat hulls and wood. To exploit FA as a polymerizable solvent, cellulose whiskers (CW) and montmorillonite clay (MMT) were used as the nanoparticle phase. Results from PNC processing show that CW and MMT can be dispersed in the PFA matrix by means of insitu polymerization, without the use of surfactants or dilution in solvents. Both CW and MMT nanoparticles catalyze the polymerization of furfuryl alcohol (FA). Moreover, the insitu intercalative polymerization of FA in the interlayer galleries of MMT leads to the complete exfoliation of the MMT in the PFA matrix. CW and MMT both function as effective matrix modifiers, increasing the thermal stability of PFA nanocomposites compared to pure PFA polymer. The increased thermal stability is seen as significant increases in the onset of degradation and in residual weight at high temperature. This research also explored the surface functionalization of Cu, Ni and Pt substrates by self-assembly of a range of difunctional linker molecules. Characterization by XPS and PM-IRRAS indicate that diisocyanides and dicarboxylic acids both form chemically "sticky" surfaces after self-assembly on Cu and Ni. Sticky surfaces may provide a means of increasing nanoparticle dispersion in metal nanocluster filled PNCs, by increasing their interaction with the matrix polymer. Another potential application for sticky surfaces on Cu is in the ongoing miniaturization of circuit boards. The functionalization of Cu bond pad substrates with linker molecules may provide an alternate means of bonding components to their bond pads, with higher placement accuracy compared to solder bumps.
9

Study of agro-composite hemp/polypropylene : treatment of fibers, morphological and mechanical characterization / Étude des agro-composites chanvre/polypropylène : traitement des fibres, caractérisation morphologique et mécanique

Han, Hongchang 04 February 2015 (has links)
L’utilisation des fibres végétales dans les polymères composites suscite de nombreuses investigations. Avant de mélanger les fibres végétales dans le polymère, un traitement chimique peut être effectué permettant de réduire l’hydrophilicité des fibres et d’améliorer l'adhérence à l’interface fibre/matrice. Dans cette thèse, l'eau et l'alcali sont utilisés d'abord pour traiter les fibres de chanvre, puis trois agents silane : 3-(triméthoxysilyl)propyl méthacrylate (MPS), N-[3- (triméthoxysilyl)propyl] aniline (PAPS) et (3-Aminopropyl)-triéthoxysilane (APS), sont utilisés pour modifier plus ou moins la surface des fibres de chanvre. Ces fibres traitées ou modifiées sont ensuite mélangées avec le polypropylène (PP) pour la fabrication des composites. Les effets de ces différents traitements sur la structure, les composants et l’hydrophilicité des fibres, et les propriétés mécaniques de ces composites sont mis en évidence. Nous avons étudié ensuite l’effet de vieillissement sur leurs comportements mécaniques, notamment l'humidité, la température et le rayonnement ultraviolet. Les résultats ont montré que le traitement de fibres par l'eau et l’alcali a des effets considérables sur la structure de fibres, les propriétés mécaniques et la durabilité des composites renforcés. La modification par l'agent de silane a une influence moins importante sur la structure des fibres, pourtant son groupe fonctionnel a une influence significative sur les propriétés mécaniques et la résistance au vieillissement des composites renforcés / Using agro fiber as reinforcement of polymer com-posites attracts numerous investigations due to the good mechanical properties and environmental benefits. Prior to blend agro fiber with polymer, chemical treatment can be employed to treat agro fiber for the purpose of reducing the hydrophilicity of fiber and improving the interfacial adhesion fi-ber/polymer matrix. In this thesis, water and alkali are utilized to treat hemp fiber firstly and then three silane agent as 3-(Trimethoxysilyl)propyl methacry-late (MPS), N-[3-(Trimethoxysilyl)propyl]aniline (PAPS) and (3-Aminopropyl)-triethoxysilane (APS) are employed to modify the hemp fiber surface. These treated or modified fibers are blended respectively with polypropylene (PP) to fabricate the hemp fiber/PP composites. The effects of these different treatments on the structure, components and hydro-philicity of fiber, and the mechanical properties of the reinforced PP composites are studied. Moreover, the accelerated ageing experiments including humidity, temperature and ultraviolet of the reinforced PP composites are conducted. The results showed that the fiber treatment of water and alkali has a considerable effect on fiber structure, mechanical properties and durability of the reinforced compo-sites. The silane agent modification of fiber has less influence on the fiber structure but its functional group has great influence on the mechanical proper-ties and ageing resistance of the reinforced compo-sites.
10

Manufacturing of hemp/PP composites and study of its residual stress and aging behavior / Elaboration des chanvre/PP composites et étude des contraintes résiduelles et du comportement de vieillissements

Zhang, Xiaohui 31 May 2016 (has links)
Depuis quelques années les matériaux composites à base de fibres naturelles sont de plus en plus utilisés pour les nouvelles performances qu’ils proposent. C’est surtout au niveau des fibres naturelles que de nouvelles propriétés sont proposées. Dans ce travail, nous nous sommes essentiellement intéressés aux fibres naturelles de chanvre. Ces fibres sont déjà fortement utilisées dans l’automobile et la construction. En Europe, ces fibres sont produites principalement en France et plus particulièrement dans l’Aube. Pour développer des agro-composites hautes performances, c’est sous la forme de fibres longues et de tissus que nous avons choisi d’orienter ce travail de thèse. Nous avons choisi la thermocompression pour élaborer des plaques avec des tissus de chanvre et une matrice en polypropylène (PP). Ce travail permet de voir l’influence des conditions d’élaboration sur le comportement mécaniques de ces agro-composites. Cette thèse permet aussi de voir l’effet du vieillissement aux UV et à l’Humidité sur les performances de ces matériaux. Enfin une analyse des contraintes résiduelles par la méthode du trou incrémental permet de voir leurs effets sur ces agro-matériaux / In recent years composite materials based on natural fibers are more and more used for their new performances. Natural fibers propose attractive environmental, mechanical and thermal properties.In this work, we are firstly interested in hemp fibers. These fibers are already used in the automotive and construction industry. In Europe, these fibers are produced mainly in France and especially in Aube. To develop agro-composites with high performances, we have focused this thesis on hemp woven. We chose to elaborate the plates with hemp woven and a polypropylene matrix (PP) by compression molding. This work allows us to see the influence of elaboration conditions on the mechanical behavior of these agro-composites. This thesis also allows us to see the effect of aging conditions UV and humidity on the performance of these materials. Finally an analysis of residual stresses determined by the hole drilling method is proposed to see their effects on the agro-materials

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