View All Items
(1 - 5 of 5)
- Title
- CALIBRATION OF ALUMINA-EPOXY NANOCOMPOSITES USING PIEZOSPECTROSCOPY FOR THE DEVELOPMENT OF STRESS-SENSING ADHESIVES.
- Creator
-
Stevenson, Amanda, Raghavan, Seetha, University of Central Florida
- Abstract / Description
-
A non-invasive method to quantify the stress distribution in polymer-based materials is presented through the piezospectroscopic calibration of alumina-epoxy nanocomposites. Three different alumina volume fraction nanocomposites were created and loaded under uniaxial compression in order to determine the relationship between applied stress and the frequency shift of the R-lines produced by alumina under excitation. Quantitative values for six piezospectroscopic coefficients were obtained...
Show moreA non-invasive method to quantify the stress distribution in polymer-based materials is presented through the piezospectroscopic calibration of alumina-epoxy nanocomposites. Three different alumina volume fraction nanocomposites were created and loaded under uniaxial compression in order to determine the relationship between applied stress and the frequency shift of the R-lines produced by alumina under excitation. Quantitative values for six piezospectroscopic coefficients were obtained which represent the stress-sensing property of the nanocomposites. The results were applied to an alumina-filled adhesive in a single lap shear configuration demonstrating the capability of the technique to monitor R-line peak positions with high spatial resolution and assess the stress distribution within the material prior to failure. Additionally, particle dispersion and volume fraction were confirmed with spectral intensities, introducing a novel experimental method for the assessment of quality in manufacturing of such nanocomposites. Results were further used to initiate studies in determining the load transfer to the nanoparticles and assessing the fundamental driving mechanisms.
Show less - Date Issued
- 2011
- Identifier
- CFE0003744, ucf:48777
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003744
- Title
- Asteroid Surfaces: The Importance of Cohesive Forces.
- Creator
-
Jardine, Keanna, Dove, Adrienne, Tetard, Laurene, Britt, Daniel, University of Central Florida
- Abstract / Description
-
Adhesive forces play a significant role on airless bodies due to their weak gravities. Investigating adhesion at the surface of asteroids and their constituent components is vital to understanding their formation and evolution. Previous research has been done to understand the interaction of micron-sized spheres to planar surfaces and sphere-to-sphere interactions, which have been used to develop models of asteroid surfaces. Our investigation experimentally investigates adhesion through...
Show moreAdhesive forces play a significant role on airless bodies due to their weak gravities. Investigating adhesion at the surface of asteroids and their constituent components is vital to understanding their formation and evolution. Previous research has been done to understand the interaction of micron-sized spheres to planar surfaces and sphere-to-sphere interactions, which have been used to develop models of asteroid surfaces. Our investigation experimentally investigates adhesion through atomic force microscopy (AFM) measurements between JSC-1 simulant particles and several AFM tips, including a typical pyramidal gold tip and microspheres of sizes 2 (&)#181;m and 15 (&)#181;m. The samples of JSC-1 consist of three size ranges: (<) 45 (&)#181;m, 75-125 (&)#181;m, and 125-250 (&)#181;m. For each sample we looked at the magnitude and distribution of the measured adhesive forces. Results show that the pyramidal tip produced larger forces than the spherical tips generally, and the sample that produced larger forces and a larger distribution of those force was the smaller, more powder-like sample with sizes (<)45 (&)#181;m.
Show less - Date Issued
- 2018
- Identifier
- CFE0007755, ucf:52377
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007755
- Title
- An Adhesive Vinyl-Acrylic Electrolyte and Electrode Binder for Lithium Batteries.
- Creator
-
Tran, Binh, Zhai, Lei, Zou, Shengli, Kuebler, Stephen, Hernandez, Florencio, Gesquiere, Andre, University of Central Florida
- Abstract / Description
-
This dissertation describes a new vinyl-acrylic copolymer that displays great potential for applications in lithium ion batteries by enabling novel, faster, safer and cost-effective processes. Understanding the chemistry of materials and processes related to battery manufacturing allows the design of techniques and methods that can ultimately improve the performance of existing batteries while reducing the cost. The first and second parts of this dissertation focuses on the free radical...
Show moreThis dissertation describes a new vinyl-acrylic copolymer that displays great potential for applications in lithium ion batteries by enabling novel, faster, safer and cost-effective processes. Understanding the chemistry of materials and processes related to battery manufacturing allows the design of techniques and methods that can ultimately improve the performance of existing batteries while reducing the cost. The first and second parts of this dissertation focuses on the free radical polymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA), methyl methacrylate (MMA), and isobutyl vinyl ether (IBVE) monomers to afford a vinyl-acrylic poly(PEGMA-co-MME-co-IBVE) random copolymer and the investigation of its properties as a soluble, amorphous, and adhesive electrolyte that is able to permanently hold 800 times its own weight. Such material properties envision a printable battery manufacturing procedure, since existing electrolytes lack adhesion at a single macromolecular level. Electrolytes can also be used as an electrode binder so long as it has structural integrity and allows ion transfer to and from the active electrode material during insertion/extraction processes. In the third section, the use of this electrolyte as a water-soluble binder for the aqueous fabrication of LiCoO2 cathodes is presented. Results of this study demonstrated the first aqueous process fabrication of thick, flexible, and fully compressed lithium ion battery electrodes by using commercial nickel foam as a supporting current collector. This feat is rather impressive because these properties are far superior to other aqueous binders in terms of material loading per electrode, specific area capacity, durability, and cell resistance. Finally, the fourth section expands on this concept by using the poly(PEGMA-co-MMA-co-IBVE) copolymer for the aqueous fabrication of a low voltage Li4Ti5O12 anode type electrode. Altogether, results demonstrate as a proof of concept that switching the current toxic manufacturing of lithium-ion batteries to an aqueous process is highly feasible. Furthermore, new electrode manufacturing techniques are also deemed possible.
Show less - Date Issued
- 2013
- Identifier
- CFE0004761, ucf:49780
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004761
- Title
- FINITE ELEMENT SIMULATION OF SINGLE-LAP SHEAR TESTS UTILIZING THE COHESIVE ZONE APPROACH.
- Creator
-
Perez, Wilson A, Gordon, Ali P., University of Central Florida
- Abstract / Description
-
Many applications require adhesives with high strength to withstand the exhaustive loads encountered in regular operation. In aerospace applications, advanced adhesives are needed to bond metals, ceramics, and composites under shear loading. The lap shear test is the experiment of choice for evaluating shear strength capabilities of adhesives. Specifically during single-lap shear testing, two overlapping rectangular tabs bonded by a thin adhesive layer are subject to tension. Shear is imposed...
Show moreMany applications require adhesives with high strength to withstand the exhaustive loads encountered in regular operation. In aerospace applications, advanced adhesives are needed to bond metals, ceramics, and composites under shear loading. The lap shear test is the experiment of choice for evaluating shear strength capabilities of adhesives. Specifically during single-lap shear testing, two overlapping rectangular tabs bonded by a thin adhesive layer are subject to tension. Shear is imposed as a result. Debonding occurs when the shear strength of the adhesive is surpassed by the load applied by the testing mechanism. This research develops a finite element model (FEM) and material model which allows mechanicians to accurately simulate bonded joints under mechanical loads. Data acquired from physical tests was utilized to correlate the finite element simulations. Lap shear testing has been conducted on various adhesives, specifically SA1-30-MOD, SA10-100, and SA10-05, single base methacrylate adhesives. The adhesives were tested on aluminum, stainless steel, and cold rolled steel adherends. The finite element model simulates what is observed during a physical single-lap shear test consisting of every combination of the mentioned materials. To accomplish this, a three-dimensional model was created and the cohesive zone approach was used to simulate debonding of the tabs from the adhesive. The thicknesses of the metallic tabs and the adhesive layer were recorded and incorporated into the model in order to achieve an accurate solution. From the data, force output and displacement of the tabs are utilized to create curves which were compared to the actual data. Stress and strain were then computed and plotted to verify the validity of the simulations. The modeling and constant determination approach developed here will continue to be used for newly-developed adhesives.
Show less - Date Issued
- 2016
- Identifier
- CFH2000149, ucf:45973
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000149
- Title
- Acute Pro-inflammatory Immune Response Following Different Resistance Exercise Protocols in Trained Men.
- Creator
-
Wells, Adam, Hoffman, Jay, Stout, Jeffrey, Fukuda, David, Oliveira, Leonardo, University of Central Florida
- Abstract / Description
-
The successful regeneration of muscle tissue is dependent upon the infiltration of phagocytic CD14++CD16- monocytes that support the proliferation and differentiation of myogenic precursor cells. Physiologically, the magnitude of the cellular response following resistance exercise is dictated by the level of receptor expression on the plasma membrane of the monocyte, as well as the secretion of their cognate ligands from tissue resident cells. However, it remains unclear whether the innate...
Show moreThe successful regeneration of muscle tissue is dependent upon the infiltration of phagocytic CD14++CD16- monocytes that support the proliferation and differentiation of myogenic precursor cells. Physiologically, the magnitude of the cellular response following resistance exercise is dictated by the level of receptor expression on the plasma membrane of the monocyte, as well as the secretion of their cognate ligands from tissue resident cells. However, it remains unclear whether the innate pro-inflammatory immune response varies with different resistance training protocols, and how it may impact recovery and the muscle remodeling process. Therefore, the purpose of this investigation was to examine temporal changes in the expression of chemotactic and adhesion receptors following an acute bout of high-volume, moderate-intensity (VOL) versus high-intensity, low-volume (HVY) lower-body resistance exercise in experienced, resistance trained men. Changes in receptor expression were assessed in conjunction with plasma concentrations of MCP-1, TNF?, and cortisol. Ten resistance-trained men (90.1 (&)#177; 11.3 kg; 176.0 (&)#177; 4.9 cm; 24.7 (&)#177; 3.4 yrs; 14.1 (&)#177; 6.1% body fat) performed each resistance exercise protocol in a random, counterbalanced order. Blood samples were obtained at baseline (BL), immediately (IP), 30 minutes (30P), 1 hour (1H), 2 hours (2H), and 5 hours (5H) post-exercise. Analysis of target receptor expression on CD14++CD16- monocytes was completed at BL, IP, 1H, 2H and 5H time points via flow cytometric analysis. Plasma concentrations of myoglobin, and LDH AUC were significantly greater following HVY compared to VOL (p = 0.003 and p = 0.010 respectively). Changes in plasma TNF?, MCP-1, and expression of CCR2, CD11b, and GCR on CD14++CD16- monocytes were similar following HVY and VOL. When collapsed across groups, TNF? was significantly increased at IP, 30P, 1H and 2H post-exercise (p = 0.001 (-) 0.004), while MCP-1 was significantly elevated at all post-exercise time points (p = 0.002 (-) 0.033). CCR2 expression was significantly lower at IP, 1H, 2H and 5H post-exercise (p = 0.020 (-) 0.040). In contrast, CD11b receptor expression was significantly greater at 1H relative to BL (p = 0.001), while GCR expression was not significantly different from baseline at any time point. As expected, plasma cortisol concentrations were significantly higher following VOL compared to HVY (p = 0.001), although this did not appear to be related to changes in receptor expression. Plasma testosterone concentrations and TNFr1 receptor expression did not appear to be affected by resistance exercise. Our results do not support a role for cortisol in the modulation of CCR2 receptors in vivo, while the degree of muscle damage does not appear to influence plasma concentrations of TNF?, or MCP-1. It is therefore likely that both HVY and VOL protocols constitute an exercise stimulus that is sufficient enough to promote a robust pro-inflammatory response, which is similar in timing and magnitude.
Show less - Date Issued
- 2015
- Identifier
- CFE0005736, ucf:50088
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005736
