Matching Items (173)
Description
This paper presents a multiscale modeling approach to simulating the self-sensing behavior of a load sensitive smart polymer material. A statistical spring-bead based network model is developed to bridge the molecular dynamics simulations at the nanoscale and the finite element model at the macroscale. Parametric studies are conducted on the developed network model to investigate the effects of the thermoset crosslinking degree on the mechanical response of the self-sensing material. A comparison between experimental and simulation results shows that the multiscale framework is able to capture the global mechanical response with adequate accuracy and the network model is also capable of simulating the self-sensing phenomenon of the smart polymer. Finally, the molecular dynamics simulation and network model based simulation are implemented to evaluate damage initiation in the self-sensing material under monotonic loading.
ContributorsZhang, Jinjun (Author) / Koo, Bonsung (Author) / Liu, Yingtao (Author) / Zou, Jin (Author) / Chattopadhyay, Aditi (Author) / Dai, Lenore (Author) / Ira A. Fulton Schools of Engineering (Contributor) / School for the Engineering of Matter, Transport and Energy (Contributor)
Created2015-08-01
Description
Identification of early damage in polymer composites is of great importance. We have incorporated cyclobutane-containing cross-linked polymers into an epoxy matrix, studied the effect on thermal and mechanical properties, and, more importantly, demonstrated early damage detection through mechanically induced fluorescence generation. Two cinnamate derivatives, 1,1,1-tris(cinnamoyloxymethyl) ethane (TCE) and poly(vinyl cinnamate) (PVCi), were photoirradiated to produce cyclobutane-containing polymer. The effects on the thermal and mechanical properties with the addition of cyclobutane-containing polymer into epoxy matrix were investigated. The emergence of cracks was detected by fluorescence at a strain level just beyond the yield point of the polymer blends, and the fluorescence intensified with accumulation of strain. Overall, the results show that damage can be detected through fluorescence generation along crack propagation.
ContributorsZou, Jin (Author) / Liu, Yingtao (Author) / Shan, Bohan (Author) / Chattopadhyay, Aditi (Author) / Dai, Lenore (Author) / Ira A. Fulton Schools of Engineering (Contributor) / School for the Engineering of Matter, Transport and Energy (Contributor)
Created2014-09-01
Description
Evidence of Six Sigma principles dates back as far as the 1800s when normal distributions were first being introduced by Friedrich Gauss. Since then, Six Sigma has evolved and been documented into the Define, Measure, Analyze, Improve, and Control (DMAIC) methodology that is used today. Each stage in the DMAIC methodology serves a unique purpose, and various tools have been developed to accomplish each stage’s goal. The manufacturing industry has developed its own more specified set of methods and tools that have been coined as Lean Six Sigma. The more notable Lean Six Sigma principles are TIMWOOD, SMED, and 5S.
As a case study, DMAIC methodology was used at a company that encourages Six Sigma in all its departments—Niagara Bottling. Ultimately, the company was able to cut its financial losses in fines from customers by over 15% in just a 12-week span by utilizing Six Sigma. In this, the importance of instilling an entire culture of Six Sigma is exemplified. When only a handful of team members are on board with the problem-solving mindset, it is significantly more difficult to see substantial improvements.
As a case study, DMAIC methodology was used at a company that encourages Six Sigma in all its departments—Niagara Bottling. Ultimately, the company was able to cut its financial losses in fines from customers by over 15% in just a 12-week span by utilizing Six Sigma. In this, the importance of instilling an entire culture of Six Sigma is exemplified. When only a handful of team members are on board with the problem-solving mindset, it is significantly more difficult to see substantial improvements.
ContributorsHumphreys, Nicholas Michael (Author) / Dai, Lenore (Thesis director) / Lin, Wendy (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
Hospital wastewater usually contains high concentrations of pharmaceuticals and other hazardous materials, depending on how waste is disposed of in a hospital. This poses potential health concerns for both the surrounding ecosystem and the contamination of drinking water. Membrane bioreactors (MBRs) are at the forefront of treating hospital wastewater due to their efficiency in dealing with high concentrations of pharmaceuticals and the relatively small size of the MBR system. Although MBRs are typically the best method of dealing with pharmaceutical-containing wastewater, an MBR is just one of many methods for treating wastewater. Engineers should be consulted to determine which water treatment systems are best for a hospital, depending on the total water usage, required size of the system, and the duration of operation for the system. Sustainable water practices can be implemented in hospitals to reduce the cost and consumption of water. Treating and reusing hospital wastewater with membrane bioreactors significantly reduces the concentration of pharmaceuticals, making hospital wastewater reusable in various parts of a hospital, which lowers the consumption of water. Furthermore, other practices can be used to minimize costs for both MBRs and total water usage within a hospital.
ContributorsSalazar, Steven Adam (Author) / Lind, Mary Laura (Thesis director) / Thomas, Elisabeth (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
Ionic liquids are salts with low melting temperatures that maintain their liquid form below 100 °C, or even at ambient temperature. Ionic liquids are conductive, electrochemically stable, non-volatile, and have a low vapor pressure, making them a class of excellent candidate materials for electrolytes in energy storage, electrodeposition, batteries, fuel cells, and supercapacitors. Due to their multiple advantages, the use of ionic liquids on Earth has been widely studied; however, further research must be done before their implementation in space. The extreme temperatures encountered during space travel and extra-terrestrial deployment have the potential to greatly affect the liquid electrolyte system. Examples of low temperature planetary bodies are the permanently shadowed sections of the moon or icy surfaces of Jupiter’s moons. Recent studies have explored the limits of glass transition temperatures for ionic liquid systems. The project is centered around the development of an ionic liquid system for a molecular electronic transducer seismometer that would be deployed on the low temperature system of Europa. For this project, molecular dynamics simulations used input intermolecular and intramolecular parameters that then simulated molecular interactions. Molecular dynamics simulations are based around the statistical mechanics of chemistry and help calculate equilibrium properties that are not easily calculated by hand. These simulations will give insight into what interactions are significant inside a ionic liquid solution. The simulations aim to create an understanding how ionic liquid electrolyte systems function at a molecular level. With this knowledge one can tune their system and its contents to adapt the systems properties to fit all environments the seismometers will experience.
ContributorsDavis, Vincent Champneys (Author) / Dai, Lenore (Thesis director) / Gliege, Marisa (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
This study aims to determine the feasibility of producing mechanophore-incorporated epoxy that can be healed. This was accomplished by grafting a synthesized mechanophore into tris(2-aminoethyl)amine to create a new epoxy hardener. Then this branched hardener was combined with a second hardener, diethylenetriamine (DETA). A proper ratio of the branched hardener to the DETA will ensure that the created epoxy will retain the force responsive characteristics without a noticeable decline in both the physical and thermal properties. Furthermore, it was desired that the natural structure of the epoxy would be left in place, and there would only be enough branched hardener present to elicit a force response and provide the possibility for healing. The two hardeners would then be added to Diglycidyl Ether of Bisphenol F (DGEBPF), which is the epoxy resin. The mechanophore-incorporated epoxy was compared to a standard epoxy—just DETA and DGEBPF—and it was determined that the incorporation of the mechanophore led to an 8.2 degrees Celsius increase in glass transition temperature, and a 33.0% increase in cross link density. This justified the mechanophore-incorporated epoxy as a feasible alternative to the standard, as its primary thermal and physical properties were not only equal, but superior. Then samples of the mechanophore-incorporated epoxy were damaged with a 3% tensile strain. This would cause a cycloreversion in the central cyclobutane inside of the mechanophore. Then they were healed with UV light, which would redimerize the severed hardener moieties. The healed samples saw a 4.69% increase in cross-link density, demonstrating that healing was occurring.
ContributorsPauley, Bradley (Author) / Dai, Lenore (Thesis director) / Gunckel, Ryan (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-12
Description
This thesis investigates an interpenetrating network of polyacrylamide and poly acrylic acid for use in a dynamic tactile display, which presents traditionally two-dimensional electronic screens as three-dimensional topographical models that can be experienced through touch. This kind of display would allow for greater access to traditionally visual information for the visually impaired. This hydrogel demonstrates Upper Critical Solution Temperature (UCST) near room temperature which facilitates a swelling transition, characterized by a sharp increase in swelling as this temperature is surpassed. Through the utilization of light responsive additives, light can trigger this shift, as the additives harness visible light, convert it into heat to raise the gel’s temperature, and increase the volume of the gel. Light-responsive additives explored include chlorophyllin, gold nanoparticles, and carbon black. Each of these additives required unique synthesis planning and strategies in order to optimize the performance of the gels. Synthesized gels were characterized using thermal swelling tests, light response tests and compression tests to determine the material strength. The best performing additive was chlorophyllin and allowed for a 20.8%±4.5% percent weight increase upon exposure to light for 10 minutes. In addition to investigating light-responsive additives, modifications were pursued to alter the overall UCST behavior, such as the addition of sodium chloride. By adding sodium chloride into the hydrogel, the gel was found to have a wider transition. Overall, light-responsive behavior was developed, and further work can be done in improving the response time and degree of swelling in order to make this material more viable for use in a dynamic tactile display.
ContributorsSitterle, Philip Kerry (Author) / Dai, Lenore (Thesis director) / Xu, Yifei (Committee member) / School of Music (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-12
Description
Statistical process control (SPC) is an important quality application that is used throughout industry and is composed of control charts. Most often, it is applied in the final stages of product manufacturing. However it would be beneficial to apply SPC throughout all stages of the manufacturing process such as the beginning stages. This report explores the fundamentals of SPC, applicable programs, important aspects of implementation, and specific examples of where SPC was beneficial. Important programs for SPC are general statistical software such as JMP and Minitab, and some programs are made specifically for SPC such as SPACE: statistical process and control environment. Advanced programs like SPACE are beneficial because they can easily assist with creating control charts and setting up rules, alarms and notifications, and reaction mechanisms. After the charts are set up it is important to apply rules to the charts to see when a system is running off target which indicates the need to troubleshoot and investigate. This makes the notification part an integral aspect as well because attention and awareness must be brought to out of control situations. The next important aspect is ensuring there is a reaction mechanism or plan on what to do in the event of an out of control situation and what to do to get the system running back on target. Setting up an SPC system takes time and practice and requires a lot of collaboration with experts who know more about the system or the quality side. Some of the more difficult parts of implementation is getting everyone on board and creating trainings and getting the appropriate personnel trained.
ContributorsSennavongsa, Christy (Author) / Raupp, Gregory (Thesis director) / Dai, Lenore (Committee member) / Materials Science and Engineering Program (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
Zeolite thin films and membranes are currently a promising technology for pervaporation, gas separation and water purification. The main drawback with these technologies is that the synthesis is not consistent leading to varied and unreproducible results. The Langmuir-Blodgett technique is a robust method for transferring monolayers of molecules or crystals to a solid substrate. By measuring the surface pressure and controlling the area, reliable results can be achieved by transferring monolayers to different solid substrates. It has been shown previously that various types of zeolites can be functionalized and dispersed on the top of water. This is done by using an alcohol to form a hydrophobic coating on the surface of zeolite. The Langmuir-Blodgett can be used to create thin, compact films of zeolites for synthesizing and growing zeolite films. For the first reported time, cubic LTA Zeolites monolayers have been assembled with the Langmuir-Blodgett technique with multiple solvents and different sizes of zeolites. These films were characterized with Scanning Electron Microscopy and Pressure-Area Isotherms generated from the Langmuir-Blodgett. It was found that linoleic acid is a required addition to the zeolite dispersions to protect the mechanical stability during agitation. Without this addition, the LTA zeolites are broken apart and lose their characteristic cubic structure. This effect is discussed and a theory is presented that the interparticle interactions of the long alkane chain of the linoleic acid help reduce the shear stress on the individual zeolite particles, thus preventing them from being broken. The effect of size of the zeolites on the monolayer formation was also discussed. There seemed to be little correlation between the monolayer quality and formation as size was changed. However, to optimize the process, different concentrations and target pressures are needed. Lastly, the effect of the solvent was explored and it was found that there is a different between monolayer formations for different solvents likely due to differing interparticle interactions. Overall, LTA zeolites were successfully fabricated and the important factors to consider are the zeolite size, the solvent, and the amount of surfactant stabilizer added.
ContributorsDopilka, Andrew Michael (Author) / Lind, Mary Laura (Thesis director) / Cay, Pinar (Committee member) / Materials Science and Engineering Program (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
This study aims to provide a foundation for future work on photo-responsive polymer composite materials to be utilized in additive manufacturing processes. The curing rate of 2,2-dimethoxy-2-phenyl-acetophenone (DMPA) in thin (<20 µm) and thick (>2 mm) layers of DMPA and poly(ethylene glycol) diacrylate (PEG-DA) mixtures was assessed for 5.0 w/v% (grams per 100 mL) concentrations of DMPA dissolved in PEG-DA. The polymerization rate and quality of curing was found to decrease as the concentration of DMPA increased beyond 1.0 w/v%; thus, confirming the existence of an optimum photo-initiator concentration for a specific sheet thickness. The optimum photo-initiator concentration for a 3-3.1 mm thick sheet of PEG-DA microstructure was determined to be between 0.3 and 0.38 w/v% DMPA. The addition of 1,6-hexanediol or 1,3-butanediol to the optimum photo-initiator concentrated solution of DMPA and PEG-DA was found to increase the Tg of the samples; however, the samples could not fully cure within 40-50 s, which suggested a decrease in polymerization rate. Lastly, the DMPA photo-initiator does not produce gaseous byproducts and is translucent when fully cured, which makes it attractive for infusion with strengthening materials because quality light penetration is paramount to quick polymerization rates. It is recommended that more trials be conducted to evaluate the mechanical properties of the optimum curing rate for DMPA and PEG-DA microstructures as well as a mechanical property comparison following the addition of either of the two alcohols.
ContributorsPiper, Tyler Irvin (Author) / Green, Green (Thesis director) / Lind, Mary Laura (Committee member) / School of Sustainability (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12