<p>This investigation delineates the optimal synthesis and characterization of innovative epoxy-carbon nanotube (CNT) nanocomposite filaments via electrospinning. Electrospinning thermosetting materials such as epoxy resins presents significant challenges due to the polycationic behavior arising from intermolecular noncovalent interactions between epoxide and hydroxyl groups, resulting in a substantial increase in solution surface tension. In this study, electrospinning submicron epoxy filaments was achieved through partial curing of epoxy via a thermal treatment process in an organic polar solvent, circumventing the necessity for plasticizers or thermoplastic binders. The filament diameter can be modulated to as low as 100 nm by adjusting electrospinning parameters.</p> <p><br></p> <p>Integrating a minimal amount of CNT into the epoxy matrix yielded enhanced structural, electrical, and thermal stability. The CNTs were aligned within the epoxy filaments due to the electrostatic field present during electrospinning. The modulus of the epoxy and epoxy-CNT filaments were determined to be 3.24 and 4.84 GPa, respectively, resulting in a 49% improvement. Epoxy-CNT nanofibers were directly deposited onto carbon fiber reinforced polymer (CFRP) prepreg layers, yielding augmented adhesion, interfacial bonding, and significant mechanical property enhancements. The interlaminar shear strength (ILSS) and fatigue resistance demonstrated a 29% and 27% increase, respectively, under intense stress conditions. Up to 45% of the Barely Visible Impact Damage (BVID) energy absorption was increased. In addition, the strategic incorporation of CNT (multi-walled) networks between the layers of CFRP resulted in a significant increase in thermal and electrical conductivities.</p> <p>This study also introduces a scalable fabrication procedure to address large volume processing, reproducibility, accuracy, and electrospinning safety. Electric fields of the experimental multi-nozzle setups were simulated to elucidate the induced surface charges responsible for the Taylor cone formation of the epoxy-CNT solution droplet on the nozzle tips. Electrospinning parameters were subsequently optimized for the multi-nozzle system and analyzed alongside simulated data to improve stability and synthesize fibers with smaller diameters.</p> <p><br></p> <p>Smaller diameter epoxy-CNT nanofibers proved critical as CNTs maintained alignment within the nanofibers when compared to larger diameter nanofibers. This research examines the impact of effective parameters on the diameter of electrospun epoxy-CNT nanofibers using artificial neural networks (ANNs). Consequently, employing a genetic algorithm (GA) and Bayesian optimization (BO) methods enable accurate prediction of epoxy-CNT nanofiber diameters prior to electrospinning. The presented models could aid researchers in fabricating electrospun thermosetting and thermoplastic scaffolds with specified fiber diameters, thereby tailoring these scaffolds for specific applications.</p>

No description available.

Magnetic nanoparticles that display high saturation magnetization and high magnetic susceptibility are of great interest for medical applications. Nanomagnetite is particularly desirable because it displays strong ferrimagnetic behavior, and is less sensitive to oxidation than magnetic transition metals such as cobalt, iron, and nickel. Magnetite nanoparticles can be prepared by co-precipitating iron (II) and iron (III) chloride salts in the presence of ammonium hydroxide at pH 9-10. One goal of this work has been to develop a generalized methodology for stabilizing nanomagnetite dispersions using well-defined, non-toxic, block copolymers, so that the resultant magnetite-polymer complexes can be used in a range of biomedical materials. Hydrophilic triblock copolymers with controlled concentrations of pendent carboxylic acids were prepared. The triblock copolymers contain carboxylic acids in the central urethane segments and controlled molecular weight poly(ethylene oxide) tail blocks. They were utilized to prepare hydrophilic-coated iron oxide nanoparticles with biocompatible materials for utility in magnetic field guidable drug delivery vehicles. The triblock copolymers synthesized contain 3, 5, or 10 carboxylic acids in the central segments with Mn values of 2000, 5000 or 15000 g/mol poly(ethylene oxide) tail blocks. A method was developed for preparing ~10 nm diameter magnetite surfaces stabilized with the triblock polymers. The carboxylic acid is proposed to covalently bind to the surface of the magnetite and form stable dispersions at neutral pH. The polymer-nanomagnetite conjugates described in this thesis have a maximum of 35 wt. % magnetite and the nano-magnetite particles have an excellent saturation magnetization of ~66 - 78 emu/g Fe3O4. Powder X-ray diffraction (XRD) confirms the magnetite crystal structure, which appears to be approximately single crystalline structures via electron diffraction spectroscopy analysis (EDS). These materials form stable magnetic dispersions in both water and organic solvents. / Ph. D.

The Tom's Creek Bridge is a small-scale demonstration project involving the use of fiber-reinforced polymer (FRP) composite girders as the main load carrying members. The project is intended to serve two purposes. First, by calculating bridge design parameters such as the dynamic load allowance, transverse wheel load distribution and deflections under service loading, the Tom's Creek Bridge will aid in modifying current AASHTO bridge design standards for use with FRP composite materials. Second, by evaluating the FRP girders after being exposed to service conditions, the project will begin to answer questions about the long-term performance of these advanced composite material beams when used in bridge design. This thesis details the In-Service analysis of the Tom's Creek Bridge. Five load tests, at six month intervals, were conducted on the bridge. Using mid-span strain and deflection data gathered from the FRP composite girders during these tests the above mentioned bridge design parameters have been determined. The Tom's Creek Bridge was determined to have a dynamic load allowance, IM, of 0.90, a transverse wheel load distribution factor, g, of 0.101 and a maximum deflection of L/488. Two bridge girders were removed from the Tom's Creek Bridge after fifteen months of service loading. These FRP composite girders were tested at the Structures and Materials Research Laboratory at Virginia Tech for stiffness and ultimate strength and compared to pre-service values for the same beams. This analysis indicates that after fifteen months of service, the FRP composite girders have not lost a significant amount of either stiffness or ultimate strength. / Master of Science

The full text will be available at the end of the embargo: 26th April 2025

The Route 601 Bridge in Sugar Grove, Virginia spans 39 ft over Dickey Creek. The Bridge is the first to use the Strongwell 36 in. fiber reinforced polymer (FRP) double web beam (DWB) in its superstructure. Replacement of the old bridge began in June 2001, and construction of the new bridge was completed in October 2001. The bridge was field tested in October 2001 and June 2002. This thesis details the field evaluation of the Rt. 601 Bridge. Using mid span deflection and strain data from the October 2001 and June 2002 field tests, the primary goal of this research was to determine the following AASHTO bridge design parameters: wheel load distribution factor g, dynamic load allowance IM, and maximum deflection. The wheel load distribution factor was determined to be S/5, a dynamic load allowance was determined to be 0.30, and the maximum deflection of the bridge was L/1500. Deflection results were lower than the AASHTO L/800 limit. This discrepancy is attributed to partial composite action of the deck-to-girder connections, bearing restraint at the supports, and contribution of guardrail stiffness. Secondary goals of this research were to quantify the effect of diaphragm removal on girder distribution factor, determine torsion and axial effects of the FRP girders, compare responses to multiple lane symmetrical loading to superimposed single lane response, and compare the field test results to a finite element and a finite difference model. It was found that diaphragm removal had a small effect on the wheel load distribution factor. Torsional and axial effects were small. The bridge response to multilane loading coincided with superimposed single lane truck passes, and curb-stiffening effects in a finite difference model improved the accuracy of modeling the Rt. 601 Bridge behavior. / Master of Science

The Route 601 Bridge spans 39 ft over Dickey Creek in Sugar Grove, VA and represents the first use of Strongwell's 36 in. double web beam (DWB) as the main load carrying members for a traffic bridge. The bridge was designed for AASHTO HS20-44 and AASHTO alternate military loading with a targeted deflection limit of L/800. For the preliminary design, conservative properties for the 36 in. DWB were assumed based on experience at Virginia Tech with Strongwell's 8 in. DWB used in the Tom's Creek Bridge. An elastic modulus (E) of 6,000 ksi and a shear stiffness (kGA) of 20,000 ksi-in2 were assumed and used with Timoshenko shear deformable beam theory to characterize the beams and determine the deflections. This thesis details the experimental work conducted in conjunction with the design of the Route 601 Bridge, which had two goals. First, a deck-to-girder connection was tested to determine if a bolted connection could develop composite action between the girder and the deck. This connection was shown to provide a significant amount of composite action when used with the 8 in. DWB and a composite deck, but little or no composite action when used with the 36 in. DWB and a glue-laminated timber deck. Second, eleven 36 in. DWB's were tested to determine their stiffness properties (EI and kGA) to insure that these properties were above the values assumed in the preliminary design, and all the beams had stiffness properties that were close to or above the assumed values. The eleven beams were also proof tested to a moment equivalent to five times the service load moment to insure the safety of the Route 601 Bridge, and one beam was tested to failure to determine the failure mode and residual stiffness of the 36 in. DWB. Finally, based on these results eight beams were chosen for the Route 601 Bridge. / Master of Science

Yes / This paper presents an analytical method for estimating the flexural strength of reinforced concrete beams strengthened with externally bonded fibre reinforced polymer (FRP) laminates. The method is developed from the strain compatibility and equilibrium of forces. Based on the size of external FRP laminates, several flexural failure modes may be identified, namely tensile rupture of FRP laminates and concrete crushing before or after yielding of internal steel reinforcement. Upper and lower limits to the size of FRP laminates used are suggested to maintain ductile behaviour of strengthened reinforced concrete sections. Comparisons between the flexural strength obtained from the current method and experiments show good agreement. Design equations for calculating the size of FRP laminates externally bonded to reinforced concrete sections to enhance their flexural strength are proposed.

Inledning: Kantbalkar på broar är en utsatt konstruktionsdel som ofta har beständighetsproblem och betongkantbalkar är svåra att utföra till den kvalitet som krävs. I denna studie undersöks möjligheten att byta ut den traditionella betongkantbalken till en fiberförstärkt polymerkomposit (FRP-komposit) med avseende på trafiksäkerhet, beständighet och lönsamhet. Studien omfattar endast brokantbalkar och inte hela brokonstruktioner. Metod: Studien omfattar litteraturstudie och beräkningar. Insamling av information till litteraturstudien sker genom sökning i forskningsdatabaser. Beräkningar utförs genom handberäkningar och med hjälp av programvara. FEM Design 17 används för att ta fram inre spänningar i konstruktionen och Granta EduPack används för att hitta material som uppfyller kraven. Beräkningar utförs i enlighet med Eurokoderna. Resultat: Spänningar i konstruktionen uppgick som högst till 151 MPa. De karakteristiska hållfasthetsvärdena i materialet behövde som högst motsvara minst 240 MPa när reduktionsfaktorer bestämts. Av totalt 782 tillgängliga FRP-kompositer i Granta EduPack fanns 18 som klarade samtliga krav på bärförmåga. Litteraturstudien fann flera tidigare studier där FRP-kompositer använts i brokonstruktioner med goda resultat angående beständighet och långsiktig lönsamhet.Diskussion och slutsatser: Flera antaganden gjordes i beräkningarna, vilka förenklar modellen och påverkar resultatets pålitlighet. Vidare påverkas resultatet av både konstruktionens design och profilers tjocklek. Resultatet av beräkningarna skulle dock kunna användas som en uppskattning av de hållfasthetsvärden som FRP-kompositer behöver uppnå i en kantbalkskonstruktion. Resultatet av litteraturstudien indikerar att en brokantbalk i FRPkomposit skulle vara fördelaktigt beständighetsmässigt, samt att det skulle kunna vara ekonomiskt lönsamt i längden, men det behövs vidare studier för att bekräfta detta. / Introduction: Edge girders on bridges are an exposed structural part that often has durability problems and concrete edge girders are difficult to produce to the required quality. In this study, the possibility of replacing the traditional concrete edge girder with a fibre reinforced polymer composite (FRP-composite) is investigated regarding traffic safety, durability, and profitability.The study covers only bridge edge girders and not entire bridge structures. Method: The study includes literature study and calculations. Collection of information for the literature study is done by searching in research databases. Calculations are performed by hand calculations and with the help of software. FEM Design 17 is used to produce internal stresses in the construction and Granta EduPack is used to find materials that meet the requirements. Calculations are conducted in accordance with the Eurocodes. Results: Stresses in the construction amounted to a maximum of 151 MPa. The characteristic strength values in the material had to correspond at most to at least 240 MPa when reduction factors were determined. Out of a total of 782 available FRP-composites in Granta EduPack, there were 18 that met all the load-bearing capacity requirements. The literature study found several previous studies where FRP-composites were used in bridge structures with good results regarding durability and long-term profitability. Discussion and conclusions: Several assumptions were made in the calculations, which simplify the model and affect the reliability of the results. Furthermore, the result if affected by both the design of the construction and the thickness of the profiles. However, the result of the calculations could be used as an estimate of the strength values that FRP-composites need to achieve in an edge girder construction. The results of the literature study indicate that a bridge edge girder in FRP-composite could be advantageous in terms of durability, and that it could be economically profitable in the long run, but further studies are needed to confirm this

Roller conveyors are critical components in various industries for material handling, enabling the efficient transportation of items in assembly lines, warehouses, and distribution centers. Traditionally constructed from materials such as steel, aluminum, or plastic, roller conveyors are now being innovatively designed using composite materials. This study investigates the design, analysis, and optimization of roller conveyors utilizing composite materials to achieve weight reduction while maintaining or enhancing structural integrity and operational efficiency. Composite materials offer enhanced properties compared to their individual components. Typical composites include fibers like carbon, glass, or aramid within a matrix of epoxy resin, providing superior strength, corrosion resistance, and customization capabilities. The research employs finite element analysis (FEA) and other advanced modeling techniques to evaluate the performance of composite roller conveyors under various loading conditions. The findings suggest that using composite materials can significantly reduce the weight of roller conveyors, leading to decreased energy consumption, lower operational costs, and improved handling efficiency. The optimized design enhances productivity and contributes to sustainability by minimizing environmental impact. This thesis advances the understanding of composite-based roller conveyors, demonstrating their potential to replace conventional materials and achieve higher efficiency in industrial applications.