Engineering Commons^™

The Effect Of Through Thickness Reinforcement Angle On The Disbonding Behavior In Skin-Stringer Configuration, Christopher John Morris

Mechanical & Aerospace Engineering Theses & Dissertations

Post-cure through thickness reinforcement is a method used to increase the mechanical properties of composite laminates in the transverse direction. This study conducted a test on skin-stringer structures bonded together in three configurations using an epoxy or thermoplastic adhesive at the interface with reinforcing pins inserted through the laminate thickness located at the edge of the stringer at differing angles between -30º and 30º. The fabrication of these samples in configurations B and C consisted of the use of carbon fiber prepeg laminate at a ply orientation of [0₂90₂]_2s for the skin and [0 90] …

Interfacial Thermomechanical Behavior Of Hybrid Carbon Fibers, Sriraj Srihari

Doctoral Dissertations and Master's Theses

The carbon fiber/epoxy interface is of great importance in composite design due to its load transfer mechanisms from the weak epoxy to the stronger fiber. Improving the strength of the interface reduces the risk of failure at the interface and improves the load transfer to the fiber. In this study, two types of nano-species ZnO nanowires and nickel-based metal organic frameworks were grown on carbon fibers to improve the interfaces. The interfacial mechanics of the enhanced fibers are evaluated using nanoindentation studies. Composite samples with Aeropoxy matrix and vertically aligned fibers are fabricated for this purpose. A Bruker TI-980 TriboIndenter …

Chemical And Physical Interaction Mechanisms And Multifunctional Properties Of Plant Based Graphene In Carbon Fiber Epoxy Composites, Daniel W. Mulqueen

Mechanical & Aerospace Engineering Theses & Dissertations

Graphene has generated substantial interest as a filler due to its exceptional strength, flexibility, and conductivity but faces obstacles in supply and implementation. A renewable, plant-based graphene nanoparticle (pGNP) presents a more accessible and sustainable filler with the same properties as mineral graphenes. In this study, the mechanisms of graphene reinforcement in carbon fiber reinforced plastic (CFRP) were examined, along with the resulting improvements to mechanical strength, resistance to crack propagation, electrical and thermal conductivity at elevated temperatures. pGNP, produced from renewable biomass, was shown to have a graphitic structure with flakes 3-10 layers thick and a median lateral size …

The Modernization Of Large Power Transformer Tanks, Babajide O. Williams

Electronic Theses and Dissertations

Due to the current demands placed on the power grid in terms of climate change, increasing urbanization, and terrorist attacks, the U.S. government in response to these demands, mandated that all the grid components be modernized in order to increase their reliability. As a critical component of the grid, Large Power Transformers (LPTs) play a key role in ensuring sustainable power generation and distribution. A literature search performed in this work and the analysis of data retrieved from the search showed that the tanks of these LPTs are critical to their durability, longevity, and reliability. Therefore, the reliability of LPTs …

Study Of A Carbon Fiber Reinforced Polymer Composite Using A Biobased Polyurethane As A Thermosetting Resin, Teddy Mageto

Electronic Theses & Dissertations

Carbon Fiber Reinforced Polymer composites (CFRP) have garnered increasing interest in recent years especially in the aerospace and automobile industries where they are gradually replacing metals as structural materials. This is owing to their light weight, high strength, high modulus, and excellent strength-to-weight ratio. Polymers are typically used as thermosetting resins in these composites. However, the synthesis of polymers currently is conducted via petrochemical processes which leads to adverse effects on the environment. To this end, in this work a biobased Polyurethane (PU) was used as a thermosetting resin in a CFRP. The biobased PU was synthesized by the reaction …

Shape Memory Polymer-Based Multifunctional Syntactic Foams, Siavash Sarrafan

LSU Doctoral Dissertations

With the increase in popularity of shape memory polymers (SMPs), especially in applications such as aerospace, textile, biomedical engineering, and even structures, the weight of the material and the devices made with it has always been a crucial factor. Using the shape memory polymer as a matrix to make a syntactic foam is one of the best and most affordable approaches to creating a lighter material that still has the shape memory effect. The addition of particles of different stiffness, strength, and size, with variable fractions, creates a composite that enables engineering the mechanical, as well as other physical and …

Contact Dewatering Of Cellulose Nanofibers For Biopolymer Composite Applications, Alexander Collins

Electronic Theses and Dissertations

Cellulose Nanofibrils (CNFs) are promising materials for reinforcement of polymer matrices attributable to their impressive physical and mechanical properties, as well as their biodegradability. However, the utilization of these materials in composites is made challenging by the water content of CNF slurries, the tendency of CNFs to agglomerate as they dry, and incompatibility between hydrophilic CNFs and hydrophobic polymer matrices. The most commercially viable drying methods to produce small-scale dry CNFs, such as spray drying, are very energy intensive, can only dry the materials down to micron-scale agglomerates, and do not preserve fibrillar aspect ratios. “Contact dewatering,” or the removal …

3d Printed Multicomponent Polymer Based Materials Via Hybrid Filaments: Fabrication And Characterization, Erik Antonio

All Dissertations

Additive manufacturing, also known as 3D printing, promises a manufacturing revolution for both industry and academic circles. One of the most widely used method of 3D printing is Fused Deposition Modeling (FDM) or Fused Filament Fabrication (FFF), which requires a thermoplastic filament to be directed towards a heating block and then deposited via extrusion layer by layer to produce a finished part. However, there are significant issues with this technology, mainly a limitation on the materials available for use and mechanical property deficiencies when compared to traditional manufacturing. These issues are brought about by the temperature limited nature of the …

Investigation Of The Effects Of Cladding Layers On Longitudinal And Transverse Mechanical Properties In Composite Laminates, Rachel Potratz, Tiffany Foo, Joseph Kamlet

Materials Engineering

The addition of cladding layers to composite laminates is used in industry to improve bond adhesion and the ease of manufacturing. However, there is no public data on the effects of cladding layers on the mechanical properties of composite components. To directly observe how cladding layers affect mechanical properties, four laminates with zero, one, two, and three cladding layers of twill fabric were added symmetrically to a biased core. The mechanical testing performed was tensile, short beam strength, and compression testing in the longitudinal and transverse directions. The measured strengths were related to the longitudinal properties of the core, and …

Non-Destructive Material Analysis Of Metals And Composites Via Thermography, Jonathan R. Doubt, James L. Chapman

Materials Engineering

The Naval Surface Warfare Center, Port Hueneme Division, is interested in the development of non-destructive damage assessment of shipboard materials via drones at distance. Long Pulsed Thermography (LPT), a method of non-destructive evaluation, was investigated as a possible method for detecting damage in metals (5005h24 Al alloy and 1008 carbon steel) and composites (aramid fiber honeycomb sandwich structure) at distances from 0.5 m to 3.0 m. LPT was conducted using two 1000 W can lights to heat the samples, and a FLIR E8-XT thermal camera. The images were then analyzed using ImageJ software to determine if damage could be detected …

Sol-Gel Derived Bioceramic Poly(Diethyl Fumarate – Co – Triethoxyvinylsilane) Composite, Aref Sleiman

Electronic Thesis and Dissertation Repository

Synthetic bone graft materials have become an increasingly popular choice for bone augmentation. Ceramic-based and polymer-based bone graft materials constitute the two main classes of synthetic bone graft materials. This study investigated the synthesis of novel bioactive composites for their potential use as bone graft biomaterials. Poly(diethyl fumarate-co-triethoxyvinylsilane)/bioceramic class II organic/inorganic hybrid biomaterials were synthesized via a sol gel process. These biomaterials were then reacted with an ammonium phosphate solution to prepare their respective composites. For the first time, we successfully synthesized sol-gel derived bioceramic poly(diethyl fumarate-co-triethoxyvinylsilane) composites. In vitro bioactivity evaluation of poly(diethyl fumarate-co-triethoxyvinylsilane)/bioceramic composites in simulated body fluid …

Monitoring Of State Transitions In Extreme Environment Application Materials Using Fiber Bragg Grating Sensors, Sabuj Khadka

Electronic Theses and Dissertations

By embedding both a single fiber Bragg grating (FBG) sensor and a thermocouple (TC) during the manufacturing for extreme environment applications of certain classes of materials such as metals and polymers, a novel in-situ approach was developed to precisely monitor their entire manufacturing processes. This novel monitoring technique was able to identify many characteristic points during the curing of room and high-temperature epoxies and the solidification processes of metal alloys composed of tin and bismuth which were selected in this research purely for verification purposes. Some of the characteristic points identified for the epoxies were: (i) the gel point, (ii) …

Rheological Properties Of Recyclable Polymer Matrices For Advanced Composite Applications, Rahul Shankar

Dissertations

This dissertation focuses on evaluating the rheological characteristics of a variety of recyclable polymer matrices, which can compete with thermosets in a wide range of specialized applications. Studying the fundamental solid and melt-state viscoelastic properties and establishing structure-property-processing relationships is critical for the widespread adoption of these novel recyclable polymers in commercial applications. The first chapter provides an introductory overview of the different recyclable polymer matrices and their applications including high performance thermoplastics as thermoset replacements in high energy composite manufacture, multifunctional specialty thermoplastics for additive manufacturing and next generation, reprocessable covalent adaptable networks for self-healing applications. Furthermore, the important …

Discontinuous Recycled And Repurposed Carbon Fiber Reinforced Thermoplastic Organosheet Composites, Philip R. Barnett

Doctoral Dissertations

There is a significant need for low cost, high volume composites in the automotive industry to aid in vehicle lightweighting and safety. The current state-of-the-art severely compromises the mechanical properties of composites to achieve cost and cycle time goals. In this dissertation, a novel composite format, termed discontinuous carbon fiber organosheets, using recycled and repurposed carbon fibers in a thermoplastic matrix is developed and studied. Unlike traditional composites, the long fiber length and rapid processing time yield mechanical properties and cycle times competitive with automotive metals.

Several studies were performed to characterize this new material format. First, samples were manufactured …

Finite Element Analysis Investigation Of Hybrid Thin-Ply Composites For Improved Performance Of Aerospace Structures, Alana M. Zahn

Mechanical & Aerospace Engineering Theses & Dissertations

Commercial and private aircraft have a need for strong yet light materials in order to have the most ideal performance possible. This study looks at the use of thin-ply composite materials to improve the performance of aircraft structures by means of weight savings and/or strength increase when compared to laminates that are composed of exclusively standard-ply materials. In order to perform an investigation based solely on finite element analysis, validation efforts were performed using test data from open hole tension, open hole compression, notched tension, and notched compression specimens. Once the models were validated sufficiently, the same modeling practices were …

Mechanism Of Compaction With Wrinkle Formation During Automatic Stitching Of Dry Fabrics And The Size Effect Of Compression Molded Discontinuous Fiber-Reinforced Composites, Anibal Benjamin Beltran Laredo

Mechanical & Aerospace Engineering Theses & Dissertations

With an ever-increasing demand for composites, more ways of manufacturing them are becoming popular and widely used. Stitching of dry fabrics is an efficient method for improving delamination resistance. Discontinuous fiber reinforced composites can be used as a lightweight alternative material for metals through a process of compression molding, which allows for complex shape manufacturing while offering structural grade mechanical properties.

This study demonstrates how the stitching of dry fabrics can be adapted to more complex surfaces. The consequences of stitching of curvilinear surfaces can result in defect formation. Therefore, to understand the physical formation of possible defects, experimental characterization …

Study Of Permeability Testing Methods For Composite Laminates, Thomas S. Busse, Giannina Marie M. Yu

Materials Engineering

Permeability measurements are strong indicators of the effectiveness of evacuation channels within a composite prepreg. The effectiveness of these evacuation channels directly relates to the void content within a processed composite laminate. The goal of Toray Advanced Composites was to compare two permeability tests and determine which one was more reliable, accurate, and economical. The first permeability test method was the Cirrus method, designed by Cirrus Aircraft, a customer of Toray Advanced Composites. The second test was ASTM D8132, the standard method for permeability testing. Additionally, Toray sought to investigate the effect out-time had on the permeability of three different …

Through-Thickness Reinforcement And Repair Of Carbon Fiber Based Honeycomb Structures Under Flexure And Tension Of Adhesively Bonded Joints, Aleric Alden Sanders

Mechanical & Aerospace Engineering Theses & Dissertations

Repair and reinforcement of composite honeycomb structures is an area of concern as higher demands are being placed on high strength, lightweight structural materials, such as carbon fiber reinforced plastics and corresponding honeycomb structures. A common issue with these structures is when a delamination in the facesheet may form and spread, leading to a failure scenario. An investigation of adding a through thickness reinforcement (TTR) to these structures at the sample level that undergo four-point-bending, tension, and joining methods is conducted throughout this thesis. The embedding of pultruded carbon fiber rods is found to be an ideal addition to composite …

Retrofit Of Corroded Corrugated Metal Culverts Using Gfrp Slip-Liner, Rahulreddy Chennareddy

Civil Engineering ETDs

Culverts are water conveyance structures, typically used to allow water flow and maintain a balance between the flow streams without interrupting structures such as highways and bridges. Corrugated metal pipes (CMPs) have been used as culverts in North America since the 1950s because of their low cost and simple construction method. Today, the corrosion of CMPs is a major problem faced by all U.S. Departments of Transportation. There is an urgent need to provide an efficient solution, one that is corrosion-resistant, to retrofit thousands of corroded CMPs across the country. High specific strength, high strength to weight ratio, corrosion resistance, …

Amorphous-Crystalline Brush Block Copolymers: Phase Behavior, Rheology And Composite Design, Gayathri Kopanati

Doctoral Dissertations

Bottlebrush block copolymers are polymers with chemically distinct polymer side chains grafted onto a common backbone. The unique architecture induced properties make these materials attractive for applications such as photonic materials, stimuli responsive actuators and drug delivery vehicles to name a few. This dissertation primarily investigates the phase transitions and rheological behavior of amorphous-crystalline bottlebrush brush block copolymers and their composites. The temperature induced phase behavior is investigated using time resolved synchrotron X-ray source. Irrespective of volume fraction and backbone length, the samples display strong segregation even at high temperatures (200 °C) and there is no accessible order-disorder transition in …

Molecular Weight And Thermal Properties Of Fiber Reinforced Polyamide-Based Composites Throughout The Direct Long-Fiber Reinforced Thermoplastic Process, Mingyu Yang

Electronic Thesis and Dissertation Repository

The D-LFT process is an efficient and cost-effective process and includes two twin-screwextruders, a conveyer, and a compression molding machine. It is imperative to understand how the process sequence affects molecular weight and thermal properties of composite materials during the D-LFT process. The main objective of this study was to characterize variation in molecular weight and thermal properties of two types of polyamide (PA)-based composite materials (glass fiber reinforced PA6 composites and carbon fiber reinforced PA66 composites) through the D-LFT process. Samples were taken from different locations along the D-LFT process and characterized using triple detection gel permeation chromatography (GPC), …

Structural Health Monitoring Of Composite Parts: A Review, Jacob Pessin

Honors Theses

Structural health monitoring has the potential to allow composite structures to be more reliable and safer, then by using more traditional damage assessment techniques. Structural health monitoring (SHM) utilizes individual sensor units that are placed throughout the load bearing sections of a structure and gather data that is used for stress analysis and damage detection. Statistical time based algorithms are used to analyze collected data and determine both damage size and probable location from within the structure. While traditional calculations and life span analysis can be done for structures made of isotropic materials such as steel or other metals, composites …

Bending Response Of Timber Mortise And Tenon Joints Reinforced With Filler-Modules And Frp Gussets, Andrew Robert Pacifico

Graduate Theses, Dissertations, and Problem Reports

In 2013, the California Bay Area (CBA) passed a set of ordinances to ensure that their 10,000 plus timber soft-story buildings were prepared for seismic events, through nondestructive evaluation methods. Many property owners are searching for an affordable retrofitting system that will also meet CBA’s new laws focusing on installations by the mandated deadlines in 2020. Over the past three to four decades, Fiber Reinforced Polymer (FRP) composites have found their way into the civil infrastructure sector for rehabilitation. The objective of this study is to evaluate the bending behavior retrofitted mortise and tenon timber joints reinforced with engineered wood …

Freeform Extrusion Fabrication Of Advanced Ceramics And Ceramic-Based Composites, Wenbin Li

Doctoral Dissertations

"Ceramic On-Demand Extrusion (CODE) is a recently developed freeform extrusion fabrication process for producing dense ceramic components from single and multiple constituents. In this process, aqueous paste of ceramic particles with a very low binder content ( < 1 vol%) is extruded through a moving nozzle to print each layer sequentially. Once one layer is printed, it is surrounded by oil to prevent undesirable water evaporation from the perimeters of the part. The oil level is regulated just below the topmost layer of the part being fabricated. Infrared radiation is then applied to uniformly and partially dry the top layer so that the yield stress of the paste increases to avoid part deformation. By repeating the above steps, the part is printed in a layer-wise fashion, followed by post-processing. Paste extrusion precision of different extrusion mechanisms was compared and analyzed, with an auger extruder determined to be the most suitable paste extruder for the CODE system. A novel fabrication system was developed based on a motion gantry, auger extruders, and peripheral devices. Sample specimens were then produced from 3 mol% yttria stabilized zirconia using this fabrication system, and their properties, including density, flexural strength, Young's modulus, Weibull modulus, fracture toughness, and hardness were measured. The results indicated that superior mechanical properties were achieved by the CODE process among all the additive manufacturing processes. Further development was made on the CODE process to fabricate ceramic components that have external/internal features such as overhangs by using fugitive support material. Finally, ceramic composites with functionally graded materials (FGMs) were fabricated by the CODE process using a dynamic mixing device"--Abstract, page iv.

Detection Of Buried Non-Metallic (Plastic And Frp Composite) Pipes Using Gpr And Irt, Jonas Kavi

Graduate Theses, Dissertations, and Problem Reports

This research investigated alternative strategies for making buried non-metallic pipes (CFRP, GFRP, and PVC) easily locatable using Ground Penetrating Radar (GPR). Pipe diameters up to 12" and buried with up to 4 ft. of soil cover were investigated. The findings of this study will help address the detection problem of non-metallic pipelines and speed the adoption of composite pipes by the petroleum and natural gas industry. The research also investigated the possibility of locating buried pipes transporting hot fluids using Infrared Thermography (IRT).

Results from the study have shown that, using carbon fabric and aluminum tape overlay on non‑metallic pipes …

High Temperature Polymer Composites Using Out-Of-Autoclave Processing, Sudharshan Anandan

Doctoral Dissertations

"High performance polymer composites possess high strength-to-weight ratio, corrosion resistance, and have design flexibility. Carbon/epoxy composites are commonly used aerospace materials. Bismaleimide based composites are used as a replacement for epoxy systems at higher service temperatures. Aerospace composites are usually manufactured, under high pressure, in an autoclave which requires high capital investments and operating costs. In contrast, out-of-autoclave manufacturing, specifically vacuum-bag-only prepreg process, is capable of producing low cost and high performance composites. In the current study, out-of-autoclave processing of high temperature carbon/bismaleimide composites was evaluated. The cure and process parameters were optimized. The properties of out-of-autoclave cured laminates compared …

A Comparison Study Of Composite Laminated Plates With Holes Under Tension, Joun S. Kim

Master's Theses

A Comparison Study of Composite Laminated Plates with Holes under Tension

A study was conducted to quantify the accuracy of numerical approximations to deem sufficiency in validating structural composite design, thus minimizing, or even eliminating the need for experimental test. Error values for stress and strain were compared between Finite Element Analysis (FEA) and analytical (Classical Laminated Plate Theory), and FEA and experimental tensile test for two composite plate designs under tension: a cross-ply composite plate design of [(0/90)4]s, and a quasi-isotropic layup design of [02/+45/-45/902]s, each with a single, centered hole of 1/8” diameter, and 1/4" diameter (four sets …

Polymer Foam /Fly Ash Composites: Evaluation Of Mechanical, Interfacial, Thermal, Viscoelastic And Microstructural Properties, Parisa Khoshnoud

Theses and Dissertations

Fly ash, a byproduct of coal combustion process in power plants, consists of fine, powdery particles that are predominantly spherical in shape, either solid or hollow, and mostly glassy (amorphous) in nature. It is capable of being recovered and used as a low-cost reinforcing filler. Adding fly ash particles to a thermoplastic foam poses many challenges to understanding the physical, mechanical, viscoelastic, thermal, and morphological changes to the composite. The effects of fly ash particles on the foaming process; e.g. nucleating and growth steps, cell types and size, and microstructure need to be evaluated in order to develop a commercial …

The Effect Of Biocomposite Material In A Composite Structure Under Compression Loading, Benjamin Andrew Sweeney

Master's Theses

While composite structures exhibit exceptional strength and weight saving possibilities for engineering applications, sometimes their overall cost and/or material performance can limit their usage when compared to conventional structural materials. Meanwhile ‘biocomposites’, composite structures consisting of natural fibers (i.e. bamboo fibers), display higher cost efficiency and unique structural benefits such as ‘sustainability’. This analysis will determine if the integration of these two different types of composites are beneficial to the overall structure. Specifically, the structure will consist of a one internal bamboo veneer biocomposite ply; and two external carbon fiber weave composite plies surrounding the bamboo biocomposite. To acquire results …

Charge Transport In Electronic-Ionic Composites, Long Zhang

Theses and Dissertations--Chemical and Materials Engineering

The goal of this thesis is to generate fundamental understandings of charge transport behaviors of composites consisting of garnet structured Al substituted Li₇La₃Zr₂O₁₂ (LLZO) electrolyte and LiCoO₂ electrode. In order to take full advantage of all-solid-state batteries, bulk type composite electrodes should be introduced to increase energy and power density. However, the charge utilization of bulk type composite electrodes is quite low. Understanding ionic conduction behavior is, therefore, important for improving the performance of all-solid-state batteries, because ion conduction within solids depends on effective pathways. Electronic conductivity can be easily compensated by …