Engineering Commons^™

Modeling, Simulation, And Validation Of Process-Structure-Property Relationships In Fused Filament Fabrication, Aaron Grant

Electronic Theses and Dissertations

As additive manufacturing (AM) grows in popularity, the need for better simulation tools to predict the process-structure-property relationships of AM parts becomes ever more necessary to employ the technology in design of functional parts with varying degrees of complexity and performance requirements. Many simulation tools and techniques have been developed that aim to achieve this goal, and the main purpose of this research is to explore how well different simulation tools and modeling approaches can capture various AM-specific features such as inter-raster and end-of raster voids, and residual stresses induced by dissimilar rates of thermal expansion. Process simulation of fused …

Utilization Of Low-Lime Calcium Silicate In Hydrated And Carbonated Cementitious Materials, Mohammad Rakibul Islam Khan

Electronic Theses and Dissertations

This study investigated the potential application of wollastonite as a cementitious material in both hydrated and carbonated binder systems. Wollastonite is naturally occurring low-lime calcium silicate (CaO.SiO₂) mineral with a substantially lower carbon footprint compared to the ordinary Portland cement (OPC). The first part of this work presented the application of wollastonite as partial replacement of OPC in traditional hydrated cement-concrete system. Second part of this work evaluated the properties of carbonation activated binder produced using wollastonite as the primary ingredient.

For the first part of the thesis, ground wollastonite with 3.5 µm and 9 µm mean particle …

An Investigation On The Effects Of Cellulose Nanofibrils On The Performance Of Cement Based Composites, Hosain Haddad Kolour

Electronic Theses and Dissertations

Cellulose nanofibrils (CNFs) are hydrophilic biodegradable nanoparticles (typically, less than 0.2 mm in length and 20-50 nm in width) that can be extracted from various plants, trees, and recycled paper stock. Their low density, low toxicity, relatively low cost, high aspect ratio, and high specific surface enable functionalization. In this work, the effects of CNFs on selected properties of cement paste, mortar, and concrete were investigated. For the cement pastes, rheology tests using a simple rheometer showed a reduction in workability as CNF dosage increased. Free shrinkage tests showed an increase in shrinkage at high w/c ratios but a decrease …

A Laboratory Investigation Of Cement Based Materials With Cellulose Nanofibers, Parivash Takasi

Electronic Theses and Dissertations

Cellulose Nanofibers (CNFs) are used as additives in cement-based products to modify their properties. Recent studies about the effects of CNFs on cement paste showed inconsistent results for several different important properties, including compressive strength and free shrinkage. There is reason to believe that the unsystematic results of the compressive strengths were affected by the lack of uniform dispersion of CNFs. As a potential remedy, two different mixing methods were applied. The first method used a basic mixer, but aggregates were added to the cement paste mixture to improve the blending process. The second method utilized a high-speed shear mixer …

Rapid Prototyping To Roll-To-Roll Manufacturing Of Microfluidic Devices, Amber Lee Boutiette

Electronic Theses and Dissertations

Microfluidics constitutes a widely applicable field of enabling technologies with great potential to revolutionize healthcare and biotechnology. The ability to miniaturize and parallelize processes with microfluidics is seen as a solution for many problems with diagnostics technologies and accessibility. Unfortunately, fabricating microfluidics often require extremely expensive, time consuming, and specialized high-precision methods, making both prototyping and commercial-scale mass manufacturing difficult to accomplish. In this work, we evaluate the feasibility of using a unique roll-to-roll (R2R) micropatterning manufacturing process coupled with Additive Manufacturing (3D printing) to rapidly prototype and produce microfluidic devices at high-volume on film or paper backings for applications …

Elucidation Of The Factors Affecting The Production And Properties Of Novel Wood Composites Made Using Renewable Nanomaterials As A Binder, Ezatollah Amini

Electronic Theses and Dissertations

A novel application of cellulose nanofibrils (CNF) as a binding agent is proposed. In this work the utilization of CNF as a complete replacement for the conventional resin-adhesives in the formulation of particleboard (PB) was evaluated. PB panels with varying CNF contents and target densities were produced using a two-step (i.e. cold and hot) pressing process. For initial evaluation, the mechanical and physical properties of the manufactured panels were determined. The need to remove a considerable amount of water from the wood particle (WP)-CNF mixture during cold pressing, motivated the study of the furnish dewatering behavior. Dewatering was assessed through …

Development Of Finite Element Techniques To Simulate Concrete-Filled Fiber-Reinforced Polymer Tube Structures, Hakeem S. Majeed

Electronic Theses and Dissertations

This dissertation presents the development of finite-element (FE) techniques to simulate the behavior of concrete-filled fiber reinforced polymer (FRP) tubes (CFFTs) in support of more effective structural design and analysis methods for buried composite arch bridges (BCABs) that use CFFT arches as main structural members. The research includes three specific topics to make contributions in different aspects of the investigation of these complex structures.

The first topic is the nonlinear three-dimensional FE modeling of steel-free CFFT splices. For model validation, comparisons were made between the model predictions and control beam and spliced beams with and without internal collars tested by …

Damage Resistance And Tolerance Of 3d Woven Composites, Justin T. Mcdermott

Electronic Theses and Dissertations

Composite materials have been adopted into primary aircraft structures by virtue of their great strength-to-weight and stiffness-to-weight ratios, fatigue insensitivity, and corrosion resistance. These characteristics are leveraged by aircraft designers to deliver improved fuel effciency and reduced scheduled maintenance burdens for their customers. These benefits have been impressively realized in the Boeing 787 and Airbus A350 XWB, with airframes utilizing about 50% composites by weight. Tempering these successes, however, are the inherent vulnerabilities of carbon-fiber reinforced composites. When compared to conventional metallic structure, composite laminates are more sensitive to stress concentrations at mechanical fastenings and damage due to low-velocity impact. …

Modeling Response Of Water Quality To Land-Use And Climate Change In Lake Auburn, Me, Nicholas Messina

Electronic Theses and Dissertations

Lake Auburn, Maine, USA, is a historically unproductive lake that has experienced multiple algal blooms since 2011. The lake is the water supply source for a population of ~60,000. We modeled past temperature, and concentrations of dissolved oxygen (DO) and phosphorus (P) in Lake Auburn by considering the watershed and internal contributions of P as well as atmospheric factors, and predicted the change in lake water quality in response to future climate and land-use changes. A stream hydrology and P-loading model (SimplyP) was used to generate input from two major tributaries into a lake model (MyLake) to simulate physical mixing, …

Development Of An Electrical Interface For A Lateral Field Excited Sensor System, Thomas J. Leighton

Electronic Theses and Dissertations

Sensor systems are utilized to provide critical information to an end user which may range from a physician in a heath care facility to a soldier in a battle field environment. The "heart" of the sensor system is the sensing platform, examples of which include semiconductor, piezoelectric and optical devices. The responses of these sensors must be converted into a format that the user can read and interpret. This conversion is achieved through integrating the sensing platform with an electrical interface.

The focus of this thesis is the development of the first electrical interface for Quartz Crystal Microbalance (QCM) sensors …

Characterization Of Nano-Cellulose Based Composites For Biomedical Applications, Mitchell P. Chesley

Electronic Theses and Dissertations

The number of orthopedic surgeries performed globally has steadily increased over the past decade due to the standardization of procedures as well as technological advancements. During this time orthopedic devices have been composed predominantly of metals, such as Titanium, Vanadium, Molybdenum, and Stainless steel, as well as their alloys, due to the high strength and durability of these materials. However, metals may, in fact, be suboptimal for orthopedic devices. For example, metals exhibit Young’s modulus much greater than the surrounding bone, inducing localized stress-shielding promoting cortical atrophy, which can lead to osteoporosis. In recent years polymers have been successfully explored …

Development Of A Hybrid Thermoplastic Composite And Concrete Deck System, Benjamin T. Smith

Electronic Theses and Dissertations

Reinforced concrete is a widely used structural system in conventional construction. It is used to create beams, columns, slabs, walls, bridge decks, dams, and many other structures. Concrete is a relatively inexpensive material that is much stronger in compression than in tension. This leads to the need to combine concrete with other materials to make an efficient hybrid structure. In conventional construction, steel reinforcing bars (rebar) are often used to carry the tension in the structure, as they are widely available and their design is well understood. There are some situations where rebar is not effective such as highly corrosive …

Design, Analysis, And Optimization Of Compactible Origami-Inspired Shelters, Anthony M. Verzoni

Electronic Theses and Dissertations

Origami-inspired design is a growing field with numerous engineering applications, including rapidly compactable and erectable shelters with nondeformed flat panels, which are considered in this research. Shelter geometry is controlled by the shape, size, and connectivity of individual panels that must fold and unfold in a kinematically compliant manner resulting in no panel intersection. Panel size and shape are altered to yield shelter designs with varying volumetric capacities. Thin panels are initially used to study the kinematics of shelter concepts as traditional origami. With increasing panel thickness, the location of fold or hinge lines exerts a large influence on the …

Design, Construction And Application Of A Home-Built, Two-Photon Microscope, William P. Breeding

Electronic Theses and Dissertations

Two-photon microscopy (TPM) is a powerful, versatile imaging modality for the study of biological systems. This thesis overviews the relevant physics involved in TPM, design considerations and process of constructing a home-built, two-photon microscope, and provides a set of procedures to operate the system. Furthermore, this work explores several applications of TPM through the study of single-cell metabolism and imaging the cellular-material interface. Explored in particular depth was the imaging of cellulose nanofiber (CNF) materials, with the goal of understanding the three-dimensional nature of fibroblast cell growth when embedded within the materials. This work uncovered several optical properties of CNF, …

Cellulose Nanofibrils (Cnf) For Textile Applications: Production Of Neat Cnf Filaments And Reinforcement Of Natural Fiber Yarns, Shokoofeh Ghasemi

Electronic Theses and Dissertations

Being the most abundant natural polymer on earth, cellulose materials have been used in many different applications. Cellulose nanofibrils (CNF) are a relatively new group of lignocellulose resource-based nanomaterials and have been the topic of many research efforts in wood products and material science field over the recent years. Using CNF in textile applications is one way to diversify product portfolio of these materials as they contain nanoscale fibrils with high mechanical properties which can fulfil textile industry’s demand for strong natural fibers. Considering that CNF is a wood-based cellulosic material in the form of water suspension, in order to …

Potential Value-Added Utilization Of Wood Ash In Construction Materials, Naveen Saladi

Electronic Theses and Dissertations

Wood ash is a byproduct from biomass power plants. Most of the wood ash is currently being disposed of as landfilling material that causes severe economic and environmental concerns. This project focuses on the feasibility of using this wood ash in construction materials. Wood ash was found to contain varieties of mineral phases including calcium carbonate, calcium aluminate, and quartz. Based on the chemical composition, the efficacy of wood ash (i) as supplementary cementitious materials (SCM), (ii) in the controlled low strength materials (CLSM) production and (iii) Portland cement production was evaluated.

Wood ash with adequate pozzolanic properties can be …

Prediction Of Paper Coating Mechanical Behavior Based On Particle-Scale Models, Daniel H. Varney

Electronic Theses and Dissertations

The mechanical properties of pigmented coatings are important for a number of situations; including coated paper, architectural paints, and structures in flexible lithium ion batteries. Coated paper and board undergo a variety of post coating application processes which have the potential to cause serious quality problems such as cracking, picking, and crack-at-the fold (CAF). Because a large number of parameters are known to influence the results, fundamental models are needed to help describe these processes and link them to the coating formulations and to the defects.

A discrete element method (DEM) computer model was developed to describe the pigment level …

Investigating The Time-Dependent And The Mechanical Behavior Of Wood Plastic Composite Lumber Made From Thermally Modified Wood In The Use Of Marine Aquacultural Structures, Murtada A. Alrubaie

Electronic Theses and Dissertations

Wood Plastic Composite (WPC) lumber based on a patent-pending formulation is being explored for use in the manufacture of an aquaculture fish cage structure (Aquapod net pen cage), as an alternative to the current high density polyethylene (HDPE) lumber. The use of WPC lumber in structural applications in marine environments requires a comprehensive effort to understand the material viscoelastic behavior and the structural performance of the WPC lumber in marine environments where the WPC lumber is exposed to the combined effect of saltwater immersion and temperature (hygrothermal). The evaluation of the viscoelastic behavior of WPC lumber in marine environments was …

Conversion Of Pretreated Hardwood To Medium-Chain Fatty Acids For Production Of Biolubricants, Koorosh Kashkooli

Electronic Theses and Dissertations

Medium-chain fatty acids (MCFA, e.g., hexanoic, heptanoic and octanoic acid) are versatile chemical compounds that are suitable precursors for the production of high-carbon-number, value-added chemicals such as bio-based lubricants. Short-chain fatty acids (SCFA, e.g., acetic, propionic, butyric, valeric acid) and methane are the natural fermentation products of anaerobic digestion, however, they have a lower value compared to MCFAs. Our current investigation seeks to integrate the production of MCFAs through chain elongation fermentation of pretreated biomass with catalytic conversion of MCFAs to lubricant molecules. By adding reducing agents such as ethanol and lactic acid to the anaerobic digestion, and inhibiting methanogenesis, …

Tide And Storm Surge Dynamics In Estuaries Of Variable Morphology, Preston Spicer

Electronic Theses and Dissertations

Storm surges are the most destructive component of coastal storms, and climate change is predicted to enhance the frequency of intense storm events in the future. Currently, most storm surge forecasting assumes linear surges and the extent to which this assumption leads to model inaccuracies is currently unknown. The goals of this research are to characterize storm surge in estuaries and determine the contribution of nonlinear tide-surge interaction to total inland surges. A citizen science experiment was conducted in four estuaries in Maine. Results show the estuary shape influences surges through convergence, friction and man-made constrictions. These mechanisms modified total …

3d Printed Bioinspired Vascularized Polymers, Kayla Marquis

Electronic Theses and Dissertations

Biological vascular systems contain a network of three-dimensional channels that transport and deliver necessary nutrients throughout the organism. These systems are complex, adaptable, and possess the ability to detect and respond to external stimuli as needed. In this work, we mimic the complexity and adaptability of biological systems by incorporating vascular systems into polymeric materials. Vacant channels are created using a fugitive ink technique along with 3D gel printing. Upon completion of vascular channel construction, proof of principle testing is performed by inoculating the polymeric surface with bacteria and adding antibiotics to the vascular channels. The system is then characterized …

Tidal And Subtidal Processes At The Mouth Of A Macrotidal Estuary, Rachel Chambers

Electronic Theses and Dissertations

Secondary flows and mixing have been shown to influence sediment transport, the vertical salinity gradient, and the exchange flow in estuaries. Typically, these hydrodynamic properties are investigated with respect to time and depth and their variability across the estuary is neglected. However, recent studies have shown that secondary flows and mixing, along with mechanisms that influence them, can exhibit lateral variability. Additionally, the variability of these hydrodynamic properties has not been studied in macrotidal estuaries, where the increased tidal forcing could affect the strength and cross channel variability.

There are two primary objectives of this thesis. The first objective is …

Global Performance Testing, Simulation, And Optimization Of A 6-Mw Annular Floating Offshore Wind Turbine Hull, Hannah L. Allen

Electronic Theses and Dissertations

Floating offshore wind turbine (FOWT) hull technologies are evolving rapidly with many technically viable designs. However, a commercially dominant architecture has yet to emerge. This thesis presents a methodology for evaluation of the hydrodynamic performance of an annular FOWT hull. This hull shows significant promise from a manufacturing and installation standpoint, but limited performance data exists. This thesis will provide ample documentation on scale model testing of an annular FOWT hull as well as the corresponding numerical validation approach and opportunities for design improvement.

The first portion of this work involves testing a 1/100th-scale model in the Harold Alfond Wind …

Process Optimization Of Levulinic Acid Production From Seaweeds And Its Upgrading To Tdo Oil, Maurvin Patel

Electronic Theses and Dissertations

Levulinic acid (LA) is a platform chemical and it can be upgraded to various products like bio-oil. The acid hydrolysis of cellulose is a widely researched pathway to make LA. However, investments to produce LA commercially can be subjected to risks due to feedstock price volatility and high processing costs. Such risks can be reduced by expanding the feedstock portfolio to produce LA from feedstock beyond wood and improving the energy efficiency of the process. One little investigated feedstock for production of LA is macro algae (seaweed). Seaweed is potentially attractive because it has low content of lignin or 5 …

Perspectives On Water Resources Risk, Policy, And Stewardship, Anne Marie Lausier

Electronic Theses and Dissertations

Water management approaches have historically optimized water for human use and placed lower emphasis on the relationship between ecosystems and humans. Despite efforts to balance human and ecosystem needs, existing management approaches tend to prioritize some needs, knowledges, and values over others. Natural and anthropogenic changes pose challenges to water governance institutions due to policy inflexibility, and may lead to ecosystem degradation, water stress, and conflict among water users. This work seeks to redress these shortcomings through three scholarly contributions. First, a conceptual framework for Water Resources Stewardship is developed in support of equitable and adaptive solutions under changing conditions. …

Influence Of Mechanical Properties Of Paper Coating On The Crack At The Fold Problem, Seyyed Mohammad Hashemi Najafi

Electronic Theses and Dissertations

Paper coating layers are subject to various stresses and deformations in many converting processes such as calendering, printing, slitting, and folding of the paper. In some cases, products may crack during folding to generate a defect called cracking at the fold (CAF). The parameters that influence these defects are not well understood. The overall goal of this thesis is to better understand the CAF behavior as related to material properties of the coating layer.

A method was developed to produce free-standing pigmented coating layers thick enough to be tested in bending as well as tension. The mechanical properties of these …

Parameters That Influence The Performance Of Dispersion Barrier Coatings, Randy Raditya

Electronic Theses and Dissertations

Barrier coating layers are important in many paper grades used in food packaging and have the potential to help reduce our use of plastics in some situations. Barrier layers to produce water proof packaging such as milk or juice cartons or coffee cups are common. Water based dispersion barrier coatings have the potential to be a low-cost alternative to extrusion coated layers. Water borne coatings are reported to be easy to recycle and break down in the environment. However, barrier properties are often less than what is desired and expected for these water borne coatings. The reason for this poor …