Engineering Commons^™

Buckling Load Optimization Of Variable Stiffness Composite Plate Using Fem And Semi-Analytical Method, Jeegar Vallabhbhai Patel

Mechanical and Aerospace Engineering Theses

The advent of new composite manufacturing techniques like Automated Fiber Placement (AFP) offers greater flexibility in structural designs by allowing curvilinear fiber paths. Hence, it is now possible to change laminate stiffness locally, thereby enabling Variable Stiffness (VS) composite structures. Such structures demonstrate superior buckling performance over traditional constant stiffness structures. However, obtaining the optimum fiber paths to improve buckling performance remains an open area of research due to the complexity of determining such fiber paths. This research investigated two approaches for optimizing fiber paths; First, a Finite Element Method (FEM) approach that utilizes linear shape functions to interpolate local …

High Performance Electromagnetic Interference Shielding From Lightweight-Flexible Polymer Composite Fiber Structures, Fariha Rubaiya

Theses and Dissertations

This study focuses on the development and characterization of fiber-based polymer composite structures with the goal of developing high performance, flexible, lightweight, and cost-effective materials for electromagnetic interference shielding and piezoelectricity. Polyvinylidene fluoride (PVDF) was used as the base fiber mat while polyaniline (PANI), polypyrrole (PPY), polyindole (PIN), polydiacetylene (PDA) and Zn2GeO4 (ZGO) were incorporated via solution mixing and in-situ polymerization. The PVDF fine fiber systems were produced using the Forcespinning® method. Morphology, structure, thermal stability, electrical properties, EMI shielding effectiveness and piezoelectric performance of the fiber mats were analyzed. The composite system containing 1.25 wt. % of ZGO-PVDF displayed …

Understanding The Adhesion Mechanism In Mycelium-Assisted Wood Bonding, Wenjing Sun

Electronic Theses and Dissertations

The increasing environmental awareness has led to an increased interest in developing more sustainable materials as alternatives to petroleum-derived products. Among different nature-based products, fungal-mycelium-based bio-composites have gained considerable attention in various applications. Multiple materials with different densities and structures and potential applications can be fabricated by inoculating filamentous white-rot fungi in lignocellulosic materials and other substrates. Different from lower-density as-grown foam-like mycelium composites, higher-density mycelium-lignocellulosic panels have the potential to replace commercial particleboard and fiberboard bonded by petroleum-based resins. This kind of composite can be produced by directly adding heat and pressure to the low-density foams or by assembling …

Investigating A Finite Element Model Updating Methodology For Characterizing Mechanical Properties Of Ncf Composites, Pasworn Chanchai

Mechanical and Aerospace Engineering Theses

Composite materials have been a key breakthrough in developing aircraft structures. Their superior strength and stiffness-to-density ratio, which are unmatched by no other materials, allow engineers to create high strength and ultra-lightweight aircraft structures. Recently, non-Crimp Fabric (NCF) composites have emerged as attractive alternatives to traditional autoclave pre-impregnated composites allowing for lower production costs, better handling and improved shelf life while maintaining excellent in-plane mechanical properties compared to other types of textile composites. NCF out-of-plane mechanical properties can also be enhanced by stitching a high tensile strength yarn throughout their entire laminate thickness, improving the resistance to delamination. However, stitch-reinforced …

Inhomogeneous Composite Design For High Energy Impact Resistance Through Computational Design, Physical Testing And Analysis, And Mathematical Modeling, Trenin Bayless

Graduate Theses & Non-Theses

Research in the development of impact resistant materials has been an expanding field for the better part of a hundred years. The development of a light penetration resistant and man-portable system that can resist extreme quantities of kinetic energy has been a subject of substantial study. In particular, the use of composite materials, polymers, ceramics, and metals has been critical to the development of the field. With the advent of complex computational programs for defining material properties, it has become possible to use simulations as a starting point for the development of next generation armored systems. To that end, it …

Analysis Of Laminated Beams: A Bibliometric Review, Arati Waghmare, Sanjay Kulkarni

Library Philosophy and Practice (e-journal)

In this paper statistical analysis of literature on “Analysis of Laminated Beams” using Scopus and Web of Science database is done. Reason behind bibliometric study of literature is to understand the extent of research in this particular area. Since Scopus and Web of Science indexing are known as the most reliable sources amongst all the peer reviewed journals, literature from Scopus and Web of Science database only is taken into consideration. Benchmarks used for the analysis are publications in a year, published articles of different authors, citations of authors etc. Considered period is from 2000 to 2020. It is found …

Porous Scaffold And Soft Hydrogel Composite For Biomedical Applications, Matthew Dicerbo

Theses and Dissertations

Biophysical signals including stiffness and dimensionality influence a myriad of stem cell behaviors including morphology, mechanosensing, and differentiation. 2D stiff environments cause increased cellular spreading and induce osteogenic differentiation whereas 3D soft environments favor rounder cell morphologies attributed to a chondrogenic phenotype. The goal of this study is to create a composite that integrates these divergent biophysical signals within one system. This composite consists of a stiff and porous polycaprolactone (PCL) backbone that provides mechanical stiffness and a 2D environment. The PCL backbone is then perfused with mesenchymal stem cells (MSCs) and a soft methacrylated gelatin (GelMe) hydrogel to provide …

In Situ Characterization Of Fiber-Matrix Interface Debonding Via Full-Field Measurements, Robert Livingston

Theses and Dissertations

Macroscopic mechanical and failure properties of fiber-reinforced composites depend strongly on the properties of the fiber-matrix interface. For example, transverse cracking behavior and interlaminar shear strength of composites can be highly sensitive to the characteristics of the fiber-matrix interface. Despite its importance, experimental characterization of the mechanical behavior of the fiber-matrix interface under normal loading conditions has been limited. This work reports an experimental approach that uses in situ full-field digital image correlation (DIC) to quantify the mechanical and failure behaviors at the fiber-matrix interface. Single fiber model composite samples are fabricated from a proprietary epoxy embedding a single glass …

Autonomous Navigation Of The Surface Autonomous Vehicle For Emergency Rescue (Saver), Andrew Skow

ENGS 88 Honors Thesis (AB Students)

Once dropped into the ocean, SAVER will autonomously navigate towards the Advanced Next-Generation Emergency Locator beacon, worn by every NASA astronaut, that emits a 121.5 MHz distress signal. Using a rotating directional loop antenna SAVER is able to detect and identify the direction of the distress beacon and navigate itself towards the signal source. The autonomous navigation system is dependent on several electrical, and mechanical systems to function properly and presents a novel systems engineering problem. Given testing limitations, NASA requires that SAVER is designed to operate indoors and with an umbilical power supply. The radio direction finding (RDF) system …

Composite Pegboard, Asa J. Cusick, Luis Corrales, Joelle Hylton, Wyatt Pauley

Mechanical Engineering

Many of those with mobility limitations who are told they will need a wheelchair for the rest of their lives can actually begin to stand and walk again given the proper tools and support. The current design for a wheelchair seeking to support this process is overly complex, heavy, and exhibits some features that could potentially pose a serious health hazard to those using it. The scope of this project is to aid in the design of an adaptable composite wheelchair frame that can be both lightweight and strong, while still allowing for physical diversity of potential users. Through research …

Prediction Of In-Plane Stiffnesses And Thermomechanical Stresses In Cylindrical Composite Cross-Sections, Bryson M. Chan

Master's Theses

Accurate mechanical analysis of composite structures is necessary for the prediction of laminate behavior. Cylindrical composite tubes are a mainstay in many structural applications. The fundamental design of circular composite cross-sections necessitates the development of a comprehensive composite lamination theory. A new analytical method is developed to characterize the behavior of thin-walled composite cylindrical tubes using a modified plate theory. A generated numerical solver can predict properties such as axial stiffness, bending stiffness, layer stresses, and layer strains in composite tubes subjected to combined mechanical loading and thermal effects. The model accounts for the curvature by transforming and translating the …

Layered Bismuth Tungstate: Heterogeneous Photocatalysis For Environmental Remediation, Mirabbos Hojamberdiev, Zuhra Kadirova, Shahlo Daminova, Khasan Sharipov, Nobuhiro Matsushita

CHEMISTRY AND CHEMICAL ENGINEERING

Air and water pollution has been one of the challenging environmental issues in modern society. Since the Honda-Fujishima effect was first reported in 1972, a semiconductor-based photocatalysis has been regarded as one of the most green and economical processes for potential application in environmental remediation. Bismuth-based semiconductors are regarded as a promising group of advanced photocatalytic materials due to their suitable band gap for visible light response, an increased mobility of photo-generated charge carriers because of well-dispersed Bi 6s orbital, non-toxicity, and easy tailoring of their morphologies. To utilize its full potential in environmental remediation, various studies have been carried …

3d Printing Of Hybrid Architectures Via Core-Shell Material Extrusion Additive Manufacturing, Robert Cody Pack

Doctoral Dissertations

Biological materials often employ hybrid architectures, such as the core-shell motif present in porcupine quills and plant stems, to achieve unique properties and performance. Drawing inspiration from these natural materials, a new method to fabricate lightweight and stiff core-shell architected filaments is reported. Specifically, a core-shell printhead conducive to printing highly loaded fiber-filled inks, as well as a new low-density syntactic foam ink, are utilized to 3D-print core-shell architectures consisting of a syntactic epoxy foam core surrounded by a stiff carbon fiber-reinforced epoxy composite shell. Effective printing of test specimens and structures with controlled geometry, composition, and architecture is demonstrated …

Electroactive Polymeric Composites To Mimic The Electromechanical Properties Of Myocardium In Cardiac Tissue Repair, Kaylee Meyers, Bruce Lee, Rupak Rajachar

Michigan Tech Publications

Due to the limited regenerative capabilities of cardiomyocytes, incidents of myocardial infarction can cause permanent damage to native myocardium through the formation of acellular, non-conductive scar tissue during wound repair. The generation of scar tissue in the myocardium compromises the biomechanical and electrical properties of the heart which can lead to further cardiac problems including heart failure. Currently, patients suffering from cardiac failure due to scarring undergo transplantation but limited donor availability and complications (i.e., rejection or infectious pathogens) exclude many individuals from successful transplant. Polymeric tissue engineering scaffolds provide an alternative approach to restore normal myocardium structure and function …

Stretching The Applications Of Biomass: Development Of Lignin Based Thermoplastic Elastomers And Composite Materials, Anthony Stephen Bova

Doctoral Dissertations

Bio-based plastics and composites have seen increased industry adoption in recent years due to growing demand for materials with a low carbon footprint. The use of lignin as a feedstock for polymers has seen growing interest as the concept of an integrated cellulosic biorefinery gains traction and advances the need to use all components of separated biomass for value-added applications. Historically, use of lignin in thermoplastic and elastomeric copolymers and blends has been bottlenecked by the inability to introduce lignin content above 30 weight percent due to difficulties with interfacial adhesion of lignin with other soft segments. Efforts to overcome …

Corrosion Rate Prediction In Frp-Concrete Repair, Mohammad A. Khawaja

USF Tampa Graduate Theses and Dissertations

Research has proven that wrapping structural elements with fiber-reinforced polymers (FRPs) slows down chloride-induced corrosion rate but does not stop it. Although FRP has been used for corrosion repair for over 40 years, predictive corrosion rate models for FRP-concrete systems are limited in literature. This dissertation presents an oxygen diffusion-based predictive framework to estimate corrosion rate in FRP-concrete systems.

The dissertation has three main components. First, a core framework that is referred to as Khawaja-Sen-Bhethanabotla (KSB) model. In the KSB model, statistical methods were used to extend experimental data on oxygen permeation coefficients. These data were for one and two …

Composite-Based Additive Manufacturing Applications In The Polymer Injection Molding Cycle, Cody Bivens

Masters Theses

“The experimental method utilized in this research was the application of composite-based additive manufacturing (CBAM) mold plates in the injection molding process. The mold plates comprised carbon fibers and polyether ether ketone (PEEK) matrix. Modifications were made to the mold plates post manufacturing in order to properly adapt to the rest of the injection molding die. A custom cooling system was engineered and integrated into the injection molding machine for the CBAM mold plates. The polymer processed in the injection molding cycle for this study was Lustran 348 acrylonitrile butadiene styrene (ABS). The result of the trials conducted in this …