Materials Science and Engineering Commons^™

Polypropylene/Polyethylene Blends With Asymmetric Viscosity: Fabrication, Characterization, And Recycling Potential, Bernadine Daichendt

All Dissertations

Polyolefin materials, polypropylene (PP) and polyethylene (PE), are widely used in day-to-day life both commercially and industrially, offering versatile applications due to their mechanical and chemical properties. The high consumption rate of these materials makes them important targets for recycling efforts. However, there are multiple contributing factors leading to low recycling of PP and PE, chiefly sorting factors: chemical similarity, changed properties after multiple rounds of processing, and the use of processing aids. It is necessary to point out that, because of multiple melt processing cycles, recycled PP has decreased molecular weight due to chain scission. Conversely, recycled PE molecular …

Micro/Nanomechanical Properties Of Top-Seeded Melt Grown Ybco Single Crystals Determined Using Depth Sensing Indentation, Ugur Kolemen, Cafer Mert Yesilkanat, Fikret Yilmaz, Fatih Dogan, Orhan Uzun

Materials Science and Engineering Faculty Research & Creative Works

Mechanical properties of the bulk YBa2Cu3O7-x (YBCO) single crystal superconductor, prepared by using the Top Seeded Melt Growth (TSMG) method, were determined. Property measurements were conducted by the nanoindentation method under various loads and the micro indentation method at different temperatures. Hardness (H) and reduced elastic modulus (Er) values were calculated by using the Oliver–Pharr method. According to hf/h max values found from load- displacement curves, there is a sink in behavior around outer rim of the indents that was confirmed by atomic force microscopy (AFM) analysis. Nanoindentation analyses conducted on upper section, middle section and subsection revealed that all …

Investigating The Performance Of Fibre Reinforced Plastic Repairs To Timber Marine Civil Structures At His Majesty’S Naval Base Devonport, Anna G. Walther

The Plymouth Student Scientist

This paper explores Fibre Reinforced Plastics (FRPs) as a composite repair method to restore and enhance mechanical properties of timber marine civil structures within the context of His Majesty’s Naval Base (HMNB) Devonport. To support this, timber composite specimens were manufactured and subjected to flexural and compressive strength tests. Comparisons are made to literature sources for initial predictions, in addition to hand calculations and Finite Element Analysis (FEA) models on SolidWorks. Data demonstrates that FRPs can be used as a cost-effective and beneficial method of repairing timber marine structures. Experimental data demonstrates an ability to restore compressive strength parallel to …

Development And Testing Of A Prototype Erbium-Doped Lithium Tantalate Based Sensor For Infrastructure Crack Detection And Measurement, Alejandro Barrera

Theses and Dissertations

Ensuring the safety and longevity of infrastructure is crucial to safeguarding communities and preserving economic stability. In this study, the development of a novel sensor for detecting and characterizing cracks in infrastructure, particularly suited for deployment on Unmanned Aerial Vehicles (UAVs), is presented. The device utilizes a laser (operating at 980 nm) for excitation of erbium-doped lithium tantalate nanoparticles that emit 1550 nm wavelength, which stimulates a photodiode for data collection. The data was utilized to collect, process, and reconstruct topological information. The synthesized lithium tantalate nanoparticle samples vary in erbium doping percentages of 0.5%, 3%, and 10%. Experimental evaluation …

Advancements In Visualization, Post-Processing And Ai-Enhanced Modeling Of Multi-Scale Micromechanics For Composite Materials, Joao Guilherme Brites Rei

Masters Theses

This study addresses some of the primary deficits of a localization/homogenization workflow for composite materials by focusing on the visualization and enhancement of models based on GMC and HFGMC, with emphasis on their implementation within the NASMAT ecosystem.

This thesis details the development of two dynamic, ParaView-based plugins that convert large hierarchical simulation outputs into interactive insights. While NASMATDiscreteElement systematizes RUC creation with transparent parametrization in a reproducible GUI, NASMATExplorerRUC enables the inspection of deeply nested datasets through accurate cell picking and synchronizes comparisons between parent and child views. Additionally, a shallow U-Net neural network is optimized on HFGMC data …

Synthesis And Characterization Of Chemically Recyclable Polypropylene-Based Covalent Adaptable Networks, Andrii Tiiara

All Dissertations

Polyolefins (POs) are inexpensive engineering materials with excellent physical and mechanical properties, accounting for nearly 60% of all thermoplastics. However, large-scale recycling remains limited, with only ~15% undergoing mechanical recovery. This dissertation addresses this challenge by fragmenting and functionalizing polypropylene (PP) chains to generate macromonomers and employing them, along with industrial reactive PP macromonomers, to synthesize, depolymerize, and repolymerize chemically recyclable polypropylene-based polyolefins (CR-POs). These CR-POs incorporate ester linkages that form covalent adaptable networks (CANs), maintaining a gel fraction of ~70% while remaining melt-reprocessable via extrusion and compression molding.

First, the fragmentation of PP is investigated by microwave irradiation. Microwave …

Further Evaluation Of Speed Tables On Roadway Curves: Simulation And Expeditionary Deployments, Nathan Reineke

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

The road network leading up to a United States military base is known as an Entry Control Facility, or ECF. Entry control facilities are used to shield military installations by monitoring vehicles and refusing access to unauthorized vehicles. Passive control devices, including speed tables, are used to disrupt or delay threat vehicles attempting to navigate ECFs at high speeds. The purpose of this research was to recommend optimized configurations of speed tables in combination with roadway curves which allow safe, efficient traversal for authorized vehicles and disruption or delay for threat vehicles.

First, an analytical model of a Tesla Model …

Integrating Dft And Machine Learning To Predict Structural Properties In High Entropy Alloys, Nathan Linton

All Dissertations

In the past decade, a paradigm shift in the design of metal alloys has been observed. These new alloys are commonly referred to as high entropy alloys (HEAs), multi-principal element alloys (MPEAs), or complex, concentrated alloys (CCAs). In contrast to conventional alloys, which consist of one main element (for example 80%) with other elements in small amounts, HEAs are made of four or more main elements ranging from 5 to 35% each element. Due to the large presence of multiple elements, HEAs have shown substantial material property improvements over conventional alloys such as steel. For example, they have high ductility …

Processing-Driven Crystallization, Morphology, And Mechanics In Pekk Composites, Nicholas Ryan Enos

Dissertations

This dissertation aims to understand how thermoplastic composites can be processed at faster manufacturing rates while identifying how processing variables influence crystallization, morphology, and mechanical properties. Throughout this dissertation, the influence of nano-scale additives, carbon fibers, rapid cooling, shear, and molecular weight on polymer physics, crystallization, morphology, and mechanics is investigated.

The inclusion of carbon nanotubes and graphene nanoplatelets accelerated crystallization, increased nucleation density, reduced lamellar thickness, and shifted governing Hoffman-Lauritzen growth regimes in PEKK. Velisaris-Seferis modelling identified a surface-induced nucleation mechanism in PEKK nanocomposites, and fast scanning calorimetry allowed for the study of rapid cooling rates, helping to identify …

Effects Of Wc Additions On The Phase Formation Of (Hf,Nb,Ta,Ti,Zr)C-(Hf,Nb,Ta,Ti,Zr)B2 High Entropy Dual Phase Ceramics, Rubia Hassan, William G. Fahrenholtz, Gregory E. Hilmas

Materials Science and Engineering Faculty Research & Creative Works

High entropy dual phase (Hf,Nb,Ta,Ti,Zr)C-(Hf,Nb,Ta,Ti,Zr)B2 ultra-high temperature ceramics were produced from powders synthesized by boro-carbothermal reduction. Systematic additions of 2.5 wt%, 5 wt%, and 10 wt% WC were incorporated after powder synthesis. Additions of 2.5 wt% and 5 wt% WC dissolved into the host ceramics, resulting in complete solid solution formation and nearly full densification. In contrast, a secondary monoboride phase evolved for the composition with 10 wt% WC, in addition to the main high entropy carbide and diboride phases. Thermodynamic analysis revealed that WB formation was favorable for WC additions in the presence of metal diborides at the sintering …

Thermal Properties Of High Entropy Dual Phase (Hf,Nb,Ta,Ti,Zr,)C-(Hf,Nb,Ta,Ti,Zr)B2 Ceramics: Comparison With The High Entropy Single-Phase Ceramics And The Effect Of Wc Additions, Rubia Hassan, William G. Fahrenholtz, Gregory E. Hilmas

Materials Science and Engineering Faculty Research & Creative Works

The heat capacity, thermal diffusivity and thermal conductivity of (Hf,Nb,Ta,Ti,Zr)C-(Hf,Nb,Ta,Ti,Zr)B₂ high entropy dual phase ceramics were evaluated from room temperature to 1800 °C and compared with the constituent high entropy single phase ceramics of the same nominal compositions. Thermal conductivity of the (Hf,Nb,Ta,Ti,Zr)C-(Hf,Nb,Ta,Ti,Zr)B₂ dual phase ceramic increased from 17.7 W m⁻¹ K⁻¹ at room temperature to 54 W m⁻¹ K⁻¹ at 1800 °C. The addition of WC to the dual phase ceramic reduced its thermal conductivity. For the addition of 5 wt% WC, room temperature thermal conductivity was 16.8 W m⁻¹ K^{−1 …}

A Precipitation-Hardened High-Entropy Alloy With Excellent Mechanical Properties Additively Manufactured By In-Situ Alloying, Matthew Luebbe, Shahryar Mooraj, Jonathan Poplawsky, Hans Pommerenke, Wen Chen, Haiming Wen

Materials Science and Engineering Faculty Research & Creative Works

Studies on precipitation-hardened high-entropy alloys (PHEAs) have demonstrated high strength, good ductility, and thermal stability, making them excellent candidates for high-temperature structural applications such as nuclear reactors. However, many complex parts for those applications would need to be produced via additive manufacturing (AM), whose rapid cooling rates and multiple heating cycles could change the microstructure of the chosen alloys and accordingly their mechanical properties. A PHEA, (Fe0.3Ni0.3Mn0.3Cr0.1)88Ti4Al8, which was developed and produced via conventional manufacturing in our previous work with high strength but low ductility, was chosen to test the effects of AM on the microstructure and mechanical properties. Scanning …

Effect Of Powder Recycling On Powder Characteristics And Mechanical Properties Of Materials Produced By Laser Powder Bed Fusion (Lpbf): A Review, Mihiretu Ganta, Marta Kurek, Arezoo Emdadi, Tadeusz Łagoda, Marek Pagáč

Materials Science and Engineering Faculty Research & Creative Works

As the Laser powder bed fusion (LPBF) process advances toward industrial-scale production, the sustainability of metal powder feedstocks has become a focal point of research. The powder recycling approach, while environmentally and economically favorable, results in a series of physicochemical variations that could compromise the part quality. The resulting variation in powder characteristics with powder recycling could affect the powder layer density and melt pool dynamics, resulting in defect formation and hindering the structural integrity of LPBFed parts. These alterations pose significant constraints to mechanical performance, particularly in fatigue-sensitive applications where even minor imperfections can substantially reduce service life. The …

Variable-Temperature Plasmonic High-Entropy Carbides, Simon Divilov, Sean D. Griesemer, Robert C. Koennecker, Michael J. Ammendola, Adam C. Zettel, Hagen Eckert, Jeffrey R. Shallenberger, Xiomara Campilongo, William G. Fahrenholtz, Arrigo Calzolari, Douglas E. Wolfe, Stefano Curtarolo

Materials Science and Engineering Faculty Research & Creative Works

Effective thermal management at variable and extreme temperatures face limitations for the development of novel energy and aerospace applications. Plasmonic approaches, shown to be capable of tailoring black-body emission, could be effective if materials with high-temperature and tunable plasmonic resonance were available. Here, we report a synergy between experimental and theoretical results proving that many high-entropy transition metal carbides, consisting of four or more metals at equal molar ratio, have plasmonic resonance at room, high (>1000∘C) and variable temperatures. We also found that these high-entropy carbides can be tuned and show considerable plasmonic thermal cycling stability. This paradigm-shift approach …

Effect Of Polymer Contaminants Sourced From Coated Paper On The Performance Of The Resulting Recycled Paper, Ezekiel J. Guevarra

All Theses

The growing demand for sustainable packaging has accelerated the use of paper-based materials as alternatives to plastics. To provide barrier and functional properties, these materials are often modified with polymer coatings. While beneficial during use, such coatings can persist as contaminants during recycling, potentially disrupting fiber bonding and reducing the quality of recycled paper. This study examined the impact of extrusion-coated low-density polyethylene (LDPE) films and two aqueous dispersions (Vapor/Water-Barrier, Acrylic Film (VWAF) and Oil & Grease Barrier (OGBF)) on contaminant distribution and mechanical performance of recycled handsheets. Kraft paper coated at varying levels was repulped and formed into handsheets, …

Predicting Long-Term Creep Behavior Using Short-Term Stress Relaxation Data In Expanded Polyethylene Foam, Andrew M. Seelig

All Theses

Closed cell expanded polyethylene (EPE) foams are widely used for protective packaging due to their high energy absorption properties and recyclability. However, these foams can be subjected to sustained compressive stresses (13.78 - 36.20 kPa), depending on density and application, leading to time-dependent deformation (creep). Creep reduces cushioning performance, making its understanding critical for effective protective packaging. Two standards, ASTM D3575 and ASTM D2221, define methods for conducting compressive creep tests on foam materials, with test durations extending up to 1000 hours. Accelerated methods such as Time Temperature Superposition (TTS) and the Stepped Isostress Method (SSM) have been explored for …

Bond Behavior Of Full-Scale Beams Using Sustainable Self-Compacting Concrete, Hayder H. Alghazali, Atheer H.M. Algburi, John J. Myers

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Sustainable concrete is a step towards greener and more eco-friendly concrete construction practices, helping to solve global environmental problems. The present study focuses on the bond behavior between steel reinforcement and greener self-compacting concrete, specifically sustainable self-compacting concrete (SUS-SCC). Three SUS-SCC mixtures with different fly ash (FA) to cement replacement levels of [50, 60, and 70% (by mass)] were developed. Twelve full-scale SUS-SCC beams with a cross-section of (305 x 57) mm and a total length of 3048 mm were cast and tested using a four-point load test setup. The effect of longitudinal and lateral steel reinforcement ratios in the …

Data Driven Design Of Ultra High Performance Concrete Prospects And Application, Bryan K. Aylas-Paredes, Taihao Han, Advaith Neithalath, Jie Huang, Ashutosh Goel, Aditya Kumar, Narayanan Neithalath

Electrical and Computer Engineering Faculty Research & Creative Works

Ultra-high-performance concrete (UHPC) is a specialized class of cementitious composites that is increasingly used in various applications, including bridge decks, connections between precast components, piers, columns, overlays, and the repair and strengthening of bridge elements. The mechanical and durability properties of UHPC are significantly influenced by factors such as low water-to-binder ratios, the inclusion of supplementary cementitious materials (SCMs), and fiber reinforcement. Machine learning (ML) has been employed to predict the performance of UHPC and optimize its mixture designs by using various raw materials. This study first provides a comprehensive review of ML applications in UHPC, focusing on predicting workability, …

Emerging Solid Electrolytes For Solid-State Sodium Batteries: Synthesis And Interface Study., Xiaolin Guo

Electronic Theses and Dissertations

Over the past decade, solid-state batteries have attracted significant attention as the next-generation energy storage technology due to their higher energy density and enhanced safety. Given the abundant sodium (Na) resources relative to lithium (Li), the development of sodium-based batteries has become increasingly compelling. Within a solid-state battery, the solid electrolytes (SEs) serve the dual function of (i) electronically insulating and physically separating the electrodes, and (ii) transporting ions between the anode and cathode. To meet these essential requirements, ideal SEs must process high ionic conductivity with negligible electronic conductivity, robust structural and chemical stability, a wide electrochemical window, and …

Automation And Upgrading Of Custom Cold Wall Uhv-Cvd Reactor For Group Iv Material Development, Alexander Golden

Graduate Theses and Dissertations

Group IV alloys have shown promising results for infrared optoelectronic applications where III-V materials are currently dominant. The III-V material system has vacancies that Group IV materials can fill, most importantly complementary metal oxide semiconductor (CMOS) process compatibility making quality devices much cheaper and widely available compared to the current state of the art. Silicon, being an indirect band gap Group IV material, has poor performance in optoelectronic applications but is the dominant material for most of the electronic industry. However, when silicon is alloyed or substituted with other group IV materials, these optoelectronic properties can be enhanced and, in …