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Sustainable Composite Systems For Infrastructure Rehabilitation, Francisco J. De Caso Y Basalo

Open Access Dissertations

The development of composite materials by combining two or more constituents with improved mechanical properties, when compared to either of the constituents alone, has existed since biblical times when straw or horse hair was mixed with clay or mud to produce bricks. During the second half of the twentieth century, modern composites known as fiber reinforced polymers (FRP) - consisting of a reinforcing phase (fibers) embedded into a matrix (polymeric resin or binder) - were developed to meet the performance challenges of space exploration and air travel. With time, externally-bonded FRP applications for strengthening of reinforced concrete (RC) structures gained …

The Effects Of Adding Attachments In Conventional Composite Hybrid Joints On Tensile Strength, Peng Hao Wang

Purdue Polytechnic Directed Projects

Mechanical fasteners are commonly used in today’s composite aircraft adhesive joints. The primary purpose for using mechanical fasteners was to provide redundancy to the adhesive joints because of the uncertainties associated with an adhesive only joint. Therefore, the use of a fastener in a conventional composite hybrid joint was mainly a part of a fail-safe design. Acting as a safety backup, the fastener did not contribute tensile strength to the joint until the adhesive joint failed. When only being used for redundancy purposes in case of an adhesive joint failure, the existing fastener became simply an added weight to the …

Axisymmetric Finite Element Modeling For The Design And Analysis Of Cylindrical Adhesive Joints Based On Dimensional Stability, Paul E. Lyon

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The use and implementation of adhesive joints for space structures is necessary for incorporating fiber-reinforced composite materials. Correct modeling and design of cylindrical adhesive joints can increase the dimensional stability of space structures. The few analytical models for cylindrical adhesive joints do not fully describe the displacement or stress field of the joint.

A two-dimensional axisymmetric finite element model for the design and analysis of adhesive joints was developed. The model was developed solely for the analysis of cylindrical adhesive joints, but the energy techniques used to develop the model can be applied to other types of joints as well. …

Fabrication Of Multi-Material Structures Using Ultrasonic Consolidation And Laser-Engineered Net Shaping, John Olorunshola Obielodan

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This research explores the use of two additive manufacturing processes for the fabrication of multi-material structures. Ultrasonic consolidation (UC) and laser- engineered net shaping (LENS) processes were used for parallel systematic investigations of the process parameters and methodologies for the development of multi-material structures.

The UC process uses ultrasonic energy at low temperature to bond metallic foils. A wide range of metallic materials including nickel; titanium; copper; molybdenum; tantalum; MetPreg®; silver; stainless steel; and aluminum alloys 1100, 3003, and 6061 were bonded in different combinations. Material domains are inherently discrete in ultrasonically consolidated structures. The mechanical properties of some of …

Fabrication Of Fluorescent Nanoparticle-Polymer Composites For Photoactive-Based Materials, Brett Ellerbrock

All Theses

Nanocomposites of nanoparticles dispersed throughout a polymer matrix have been studied to great length to improve the overall polymer properties. These enhancements are observed in the thermal, physical, and/or optical characteristics. Being able to harness nanoparticles in such a way may help improve fiber technology into the 21st century.
This work was geared toward synthesizing rare earth doped lanthanum fluoride (LaF₃) nanoparticles because good separation in the absorption and emission bands of the material and it fluoresces in the visible to near-infrared range. Terbium ions were added to a LaF₃ crystal because of their distinct visible green …

Comprehensive Process Maps For Synthesizing High Density Aluminum Oxide-Carbon Nanotube Coatings By Plasma Spraying For Improved Mechanical And Wear Properties, Anup K. Keshri

FIU Electronic Theses and Dissertations

Plasma sprayed aluminum oxide ceramic coating is widely used due to its outstanding wear, corrosion, and thermal shock resistance. But porosity is the integral feature in the plasma sprayed coating which exponentially degrades its properties. In this study, process maps were developed to obtain Al2O3-CNT composite coatings with the highest density (i.e. lowest porosity) and improved mechanical and wear properties. Process map is defined as a set of relationships that correlates large number of plasma processing parameters to the coating properties. Carbon nanotubes (CNTs) were added as reinforcement to Al2O3 coating to improve the fracture toughness and wear resistance. Two …

Non-Traditional Lightweight Polypropylene Composites Reinforced With Milkweed Floss, Narendra Reddy, Yiqi Yang

Department of Textiles, Merchandising, and Fashion Design: Faculty Publications

Lightweight composites are preferred for automotive applications due to the weight restrictions and also due to the presence of inherent voids that can enhance the sound absorption of these composites. The density of the reinforcing materials plays a crucial role in such lightweight composites. Milkweed is a unique natural cellulose fiber that has a completely hollow center and low density (0.9 g cm−3) unlike any other natural cellulose fiber. The low density of milkweed fibers will allow the incorporation of higher amounts of fiber per unit weight of a composite, which is expected to lead to lightweight composites with better …

Delamination Of Sandwich Composites, Richard Anthony Davis

Aerospace Engineering

The use of shear keys to help stop or inhibit the face-sheet core delamination of sandwich composite beams under monotonic loading was analyzed in Cal Poly’s structural design lab. The composite beams were treated with the same boundary conditions as the ASTM D5528 double cantilever beam bending in which both faces of the beam remain free; one of the faces would have a debonded side and the other would not. An aluminum tab is attached to the top of the specimens and the load is applied there. Each specimen has piezoelectric sensors that are utilized in the detection of delamination …

Adapting Biodegradable Oligo(Poly(Ethylene Glycol) Fumarate) Hydrogels For Pigment Epithelial Cell Encapsulation And Lens Regeneration, Mimi W. Zhang, Hansoo Park, Xuan Guo, Kenta Nakamura, Robert M. Raphael, F. Kurtis Kasper, Antonios G. Mikos, Panagiotis A. Tsonis

Biology Faculty Publications

This study investigated the encapsulation of newt iris pigment epithelial cells (PECs), which have the ability to regenerate a lens by trans-differentiation in vivo, within a biodegradable hydrogel of oligo(poly(ethylene glycol) fumarate) crosslinked with poly(ethylene glycol)-diacrylate. Hydrogel beads of initial diameter of 1mm were fabricated by a molding technique. The swelling ratio and degradation rate of the hydrogel beads decreased with increasing crosslinking ratios. Confocal microscopy confirmed the cytocompatibility of crosslinking hydrogel formulations as evidenced by the viability of an encapsulated model cell line within a crosslinked hydrogel bead. Hydrogel beads encapsulating iris PECs were also implanted into lentectomized newts …

Electrochemical Capacitance Of Mno_2 /Pani Composite, Xiao-Cun Xu, Kai-Yu Liu, Zhi-Gang Yin, Zhe Sun, Geng Su

Journal of Electrochemistry

Nano-MnO2 was prepared by using P123 as a soft template.The MnO2 /polyaniline composite was further prepared by polymerization of aniline with the nano-MnO2 in acidic conditions and was investigated by XRD and IR.The morphology of nano-MnO2 observed by SEM was changed with the introduction of aniline.The electrochemical properties of MnO2 /PANI electrode were investigated using cyclic voltammetry,galvanostatic charge-discharge and electrochemical impedance spectroscopy.The specific capacitance of MnO2 /PANI electrode could reach as high as 190.8 F·g-1,which decayed only 4.7% over 500 cycles.And the coulombic efficiency has been maintained at above 97%.

Thermal Degradation Of High-Temperature Fluorinated Polyimide And Its Carbon Fiber Composite, Andrea D. Adamczak, Adam A. Spriggs, Danielle M. Fitch, Walid Awad, Charles A. Wilkie, Jaime C. Grunlan

Chemistry Faculty Research and Publications

No abstract provided.

Functionalization Of Multi-Walled Carbon Nanotubes And The Interactions Of Multi-Walled Carbon Nanotubes In Epoxy Composites, Christopher Fitzwater

University of Kentucky Master's Theses

Multi-walled carbon nanotubes (MWNTs) are a relatively new allotrope of carbon that have potentially useful properties that may improve polymer composites. The work of this thesis explores the interactions between MWNTs and functionalized MWNTs within epoxy matrix and the properties of the MWNT/epoxy composite. These interactions were characterized with an emphasis on finding how well the MWNT/epoxy composite flows and how conductive it is after curing.

Three-Dimensional C/Sno2 Composites As Anode Materials For Lithium Ion Batteries, C F. Zhang, M Quince, P Zhang, Z X. Chen, Z P. Guo

Faculty of Engineering and Information Sciences - Papers: Part A

The nano-carbon materials have attracted a lot of research interests since the discovery of C60 molecule in 1985 by Kroto et al. (1), and the first experimental evidence of tabular carbon structure from Iijima in 1991 (2). Current methods used for the preparation of nano-carbon materials, including chemical vapour deposition (CVD) and arc vaporisation (3), are commonly characterized by high cost and the high-pure carbonaceous precursor gasses. In this work, the potential of using coconut shell which is very cheap and readily available for the production of graphitic nano-carbon three-dimensional networks was investigated.

On The Use Of Polyurethane Matrix Carbon Fiber Composites For Strengthening Concrete Structures, Zachary Haber

Electronic Theses and Dissertations

Fiber-reinforced polymer (FRP) composite materials have effectively been used in numerous reinforced concrete civil infrastructure strengthening projects. Although a significant body of knowledge has been established for epoxy matrix carbon FRPs and epoxy adhesives, there is still a need to investigate other matrices and adhesive types. One such matrix/adhesive type yet to be heavily researched for infrastructure application is polyurethane. This thesis investigates use of polyurethane matrix carbon fiber composites for strengthening reinforced concrete civil infrastructure. Investigations on mirco- and macro-mechanical composite performance, strengthened member flexural performance, and bond durability under environmental conditioning will be presented. Results indicate that polyurethane …

Performance Of Reinforced Concrete Columns Strengthened With Fiber Reinforced Polymers Under Various Loading Conditions, Mohamed Gamal Mohamed El Sayed

Theses

Strengthening of reinforced concrete (RC) structures with Carbon Fiber Reinforced Polymer (CFRP) composites has been a popular subject that attracted considerable attention from researchers for the last two decades. The high specific strength, stiffness, environmental resistance, and ease of application make CFRP composites highly desirable for strengthening and rehabilitation of RC structural components.

For concentrically loaded RC members with a circular cross-section, the lateral CFRP-confinement of concrete results in a substantial increase in load capacity and ductility. CFRP-confinement is less effective for RC compression members with square and rectangular cross-sections due to stress concentration at the corners and lack of …

Modeling And Simulation For Shape Memory Polymer Based Self-Healing Syntactic Foam, Wei Xu

LSU Doctoral Dissertations

Syntactic foams, renowned for their low density and high mechanical properties, are enjoying continuing growth in various civilian and military sectors. However, like laminated composites, foam cored structures are vulnerable to impact damages and suffering from inabilities in repairing macro-scale cracks. A self-healing mechanism for structural damage is genuinely desired. A recent development in self-healing structural damage is a two-step close then heal (CTH) scheme proposed by Li and Nettles [1] and elucidated by Li and Uppu [2], by mimicking the self-healing process of human skin. This concept has been further demonstrated in Nji and Li’s work [3] that a …