Materials Science and Engineering Commons^™

Enhancing Electromigration Reliability In Solder Interconnects Through Microstructure Control And Thermomechanical Failure Mechanisms In Thin Metal Lines Under Surge Current Conditions, Hariram Mohanram

Material Science and Engineering Dissertations - Archive

The relentless miniaturization of semiconductor devices has intensified reliability challenges in electronic packaging, particularly for solder interconnects and thin metal lines. This dissertation investigates two critical failure mechanisms—electromigration (EM) and thermomechanical fatigue (TMF)—and explores strategies to mitigate these effects. Electromigration, driven by high-density current-induced atomic migration, significantly impacts solder interconnects. This study examines the role of Under-Bump Metallization (UBM) and solder microstructure in improving EM reliability. Findings reveal that thicker UBMs delay void nucleation and enhance EM resistance, while the absence of UBM leads to failure through vertical void propagation. Additionally, grain orientation, particularly the c-axis alignment in Sn grains, …

Effect Of Admixtures On Rapid Hardening, Self-Consolidating Concrete, Haley Johnson

Theses and Dissertations--Civil Engineering

Self-consolidating, rapid-hardening concrete is a sought-after product in the market now, however the effects of admixtures on fresh and hardened concrete rheology are still uncertain. This study aims to create a self-consolidating concrete (SCC) using calcium sulfoaluminate (CSA) cement for its rapid-hardening properties, and tests two set time retarders and two viscosity-modifying admixtures (VMAs) to determine how they affect the properties of concrete. The properties studied in this thesis are workability, viscosity, set times, air content, compressive strength, and freeze-thaw resistance of self-consolidating concrete. It was found that tartaric acid creates a very workable SCC with consistent results regardless of …

3d Flow Field Quantification In An Artery Model Using Optical Flow Method Based On Simulated Multi-Angle Angiography, Zifeng Yang, Hang Yi, Luke Bramlage, Bryan Ludwig

Mechanical and Materials Engineering Faculty Publications

3D flow field in a numerically simulated arterial model is quantified using the three-dimensional optical flow method based on simulated simultaneous multi-angle X-ray angiography of the blood flow with contrast agent perfusions.

Strategies To Mitigate Efflorescence In Walls Constructed Using Clays Bricks; A Review Article, Marwa Abdulkareem. Anber, Soran Abdulrahman Ahmad, Naros Rahman Mahmoud, Kawan Fuoad. Kayani, Mohammed Ali Abdulrehman

Al-Esraa University College Journal for Engineering Sciences

_{The construction of buildings, especially residential housing for communities, is a significant industry on a global scale. Masonry units such as bricks, blocks, and stones are often utilized materials. Bricks are highly regarded because to their widespread availability, cost-effectiveness, and excellent insulating capabilities. Nevertheless, the presence of efflorescence presents a difficulty in the construction of brick walls. Efflorescence refers to the process in which salts move to the outer layer of the brick, resulting in the formation of white deposits and negatively impacting its visual appeal. Efflorescence is caused by various circumstances, such as the existence of salts in bricks, …}

The Importance Of Cryptography In Cloud Computing, Saja Alaam Talib

Al-Esraa University College Journal for Engineering Sciences

Cloud computing has grown as a widely accepted concept simultaneously, as the alarms for the security of data and information. This paper seeks to establish the comprehensive roles of cryptography in tackling these issues in the Cloud environment. The study begins with the historical background of cryptography and then moves on to analyze trends in information technology before discussing on the challenges to security in cloud computing. The goal of its publication is to highlight the importance of using cryptographic technologies for the protection of information confidentiality, its integrity and compliance. The combination of literature review and the case study …

Restoration Of Strength In Polyamide Woven Glass Fiber Organosheets By Hot Pressing, Mohammad Nazmus Saquib, Edwing Chaparro-Chavez, Christopher Morris, Kuthan Çelebi, Diego Pedrazzoli, Mingfu Zhang, Sergii G. Kravchenko, Oleksandr G. Kravchenko

Mechanical & Aerospace Engineering Faculty Publications

Thermoplastic composite organosheets (OSs) are increasingly recognized as a viable solution for automotive and aerospace structures, offering a range of benefits including cost-effectiveness through high-rate production, lightweight design, impact resistance, formability, and recyclability. This study examines the impact response, post-impact strength evaluation, and hot-pressing repair effectiveness of woven glass fiber nylon composite OSs across varying impact energy levels. Experimental investigations involved subjecting composite specimens to impact at varying energy levels using a drop-tower test rig, followed by compression-after-impact (CAI) tests. The results underscore the exceptional damage tolerance and improved residual compressive strength of the OSs compared to traditional thermoset composites. …

Effects Of Hemp Fibers On The Mechanical Performance Of Concrete, Hamida Baassou

Masters Theses

The construction industry is known to be globally the number one contributor to greenhouse gas emissions (GHG) and energy consumption. The purpose of this study is to examine the potential use of hemp as a concrete reinforcement, its mechanical properties and strength, its environmental and socio-economic advantages, and its limitations. To examine the mechanical performance of hemp fiber, 54 specimens will be tested for compressive, tensile, and flexural strength. This was done in two parts. In the first part hemp fibers in two different ratios (0.5v% and 1v%), and two different treatments (water and 5% sodium hydroxide) were added to …

Nano-Patterned Si Structures For Optical Filters And Electro-Mechanical Relays: Fabrication, Characterization, Prospects, And Limitations, Md Ataul Mamun

Theses and Dissertations

Nanofabrication technology, especially nanopatterning, is a rapidly advancing field that has already resulted in creating novel devices and holds promise for producing even more with unmatched performance. These techniques also allow us to gain insight into physical phenomena at the micro- and nanoscale. The ultimate performance of nanofabricated devices and their compatibility with existing Si-based CMOS technology hinge upon the careful selection of materials and precise design, coordinated with meticulous pattern transfer. In this work, we applied nanopatterning techniques on silicon to create optical filters for the shortwave infrared (SWIR) region and nanoelectromechanical system (NEMS) relay-based logic gates. Additionally, these …

Insights Into The Characterization And Degradation Of Electrospun Polycaprolactone Scaffolds For Tissue Engineering Applications, Caleb B. Wells

Theses and Dissertations

Electrospun polymeric biodegradable scaffolds are essential in tissue engineering, particularly for Engineered Tissue Vascular Grafts (ETVGs), which promise advancements in treating coronary artery disease, peripheral arterial disease, congenital cardiovascular defects, and renal disease. These scaffolds present a solution to issues with autologous graft availability and durability. While large-diameter grafts in low-pressure environments have seen success, small-diameter grafts in high-flow scenarios remain challenging. Understanding polymeric scaffold degradation and behavior during incubation, especially under dynamic mechanical loading, is vital for clinical translation of small-caliber ETVGs.

This research focuses on characterizing the mechanical and microstructural properties of electrospun polycaprolactone (PCL) scaffolds and their …

Solidification Cracking In Additively Manufactured High Entropy Alloy Nicrcofe With V Or W, Andrew R. Walch

Dissertations, Master's Theses and Master's Reports

Recent sustainability efforts have reduced CO2 emissions from electricity generation by increasing operating temperatures and pressures in advanced ultra-supercritical (A-USC) power plants. However, the extreme operating conditions in these A-USC power plants require new high temperature materials. The recent study of nickel-based high-entropy alloys (HEA) represents the latest approach to meet the specifications for A-USC operations. A CALculation PHase Diagram (CALPHAD) driven Bayesian optimization method was used to design the composition of alloys composed of NiCrCoFe with V or W, which were fabricated via wire-based additive manufacturing to enable high throughput development. Although the alloy was designed to minimize solidification …

Using Tensile And Compressive Stress Superposition During Incremental Forming To Manipulate Martensitic Transformation In Ss304, Elizabeth M. Mamros, Fabian Maaß, A. Erman Tekkaya, Brad L. Kinsey, Jinjin Ha

Faculty Conference Papers and Presentations

Single point incremental forming (SPIF) is a flexible manufacturing process that has applications in industries ranging from biomedical to automotive. In addition to rapid prototyping, which requires easy adaptations in geometry or material for design changes, control of the final part properties is desired. One strategy that can be implemented is stress superposition, which is the application of additional stresses during an existing manufacturing process. Tensile and compressive stresses applied during SPIF showed significant effects on the resulting microstructure in stainless steel 304 truncated square pyramids. Specifically, the amount of martensitic transformation was increased through stress superposed incremental forming. Finite …

High-Temperature Oxidation Behavior Of High Entropy Carbide (Tanbtiv)C In Atmospheres With Different Oxygen Contents, Ruoyu Chen, Hongbin An, Jie Zhan, Saisai Li, Aiqin Mao, Haiming Wen

Materials Science and Engineering Faculty Research & Creative Works

A high entropy carbide (TaNbTiV)C was fabricated via spark plasma sintering of high entropy powders that were prepared using a molten salt method. The as-fabricated high entropy carbide was then investigated for its high-temperature oxidation behavior at 850 °C, under atmospheres with three different oxygen contents (20 vol%, 40 vol%, and 60 vol%). After the high-temperature oxidation process, the main phases observed in all the specimens were incompletely oxidized phase (Nb_xTi_1-x)C_yO_2-y and oxides (Nb_0.5Ta_0.5)₂O₅, TiO₂, and Nb₂O₅. Importantly, the …

Synergistic Hardening In A Dual Phase High-Entropy (Hf,Nb,Ta,Ti,Zr)C–(Hf,Nb,Ta,Ti,Zr)B2 Ultra-High Temperature Ceramic, Rubia Hassan, William G. Fahrenholtz, Gregory E. Hilmas, Stefano Curtarolo

Materials Science and Engineering Faculty Research & Creative Works

A dual phase high-entropy (Hf,Nb,Ta,Ti,Zr)C–(Hf,Nb,Ta,Ti,Zr)B2 ultra-high temperature ceramic was synthesized using a single step boro-carbothermal reduction route. The synthesized powder was densified by spark plasma sintering at 2000°C, resulting in complete solid solution formation and a relative density of ≈99%. The dual phase ceramic was 43 vol% high-entropy carbide and 57 vol% high-entropy boride. The grain sizes were 0.85 ± 0.34 µm for the carbide and 0.87 ± 0.33 µm for the boride with minimal residual oxide (0.2 vol%) detected in the microstructure. The resulting composition had a higher microhardness than the individual boride and carbide ceramics across the range …

Parametric Optimization Of Friction Stir Welding Of Aa6061-T6 Samples Using The Copper Donor Stir-Assisted Material Method, Aiman H. Al-Allaq, Joseph Maniscalco, Srinivasa Naik Bhukya, Zhenhua Wu, Abdelmageed Elmustafa

Mechanical & Aerospace Engineering Faculty Publications

This study presents an optimization of the process parameters for the effect of copper (Cu) donor material percentage on the friction stir welding (FSW) of AA6061-T6 alloy. Extensive factorial experiments were conducted to determine the significance of the rotational speed (ω), the transverse speed (v), the interface coefficient of friction (μ), and the Cu donor material percentage in the plunge, left, right, and downstream zones. Design Expert 13 software was used to identify the number of simulation experiments to be conducted using the Abaqus simulation software. From Design Expert 13, which is a thorough multi-objective optimization analysis software, we were …

A Comprehensive Review Of Piezoelectric Ultrasonic Motors: Classifications, Characterization, Fabrication, Applications, And Future Challenges, Sidra Naz, Tian-Bing Xu

Mechanical & Aerospace Engineering Faculty Publications

Piezoelectric ultrasonic motors (USMs) are actuators that use ultrasonic frequency piezoelectric vibration-generated waves to transform electrical energy into rotary or translating motion. USMs receive more attention because they offer distinct qualities over traditional magnet-coil-based motors, such as miniaturization, great accuracy, speed, non-magnetic nature, silent operation, straightforward construction, broad temperature operations, and adaptability. This review study focuses on the principle of USMs and their classifications, characterization, fabrication methods, applications, and future challenges. Firstly, the classifications of USMs, especially, standing-wave, traveling-wave, hybrid-mode, and multi-degree-of-freedom USMs, are summarized, and their respective functioning principles are explained. Secondly, finite element modeling analysis for design and …

Dual Airfoil Testing System, Zifeng Yang, Collin Charvat, Jack Stafford, Kyle Mathews, Logan Kelly

Mechanical and Materials Engineering Faculty Publications

A dual airfoil testing system includes a platform including a frame defining a chamber that is configured to receive a horizontal flow of air for testing a first airfoil and a second airfoil contained in the chamber and a control system including a controller to control a first attack angle stepper motor, a second attack angle stepper motor, at least one gap stepper motor, and at least one stagger stepper motor. The controller is configured to automatically control and adjust the stepper motors to control and adjust the attack angle of the first airfoil, the attack angle of the second …

Fabrication Of Smooth Sac305 Thin Film Via Magnetron Sputtering, M. Ojha, A. A. Elmustafa

Mechanical & Aerospace Engineering Faculty Publications

SAC305 (96.5 wt% Sn, 3 wt% Ag, 0.5 wt%Cu) solder is increasingly becoming popular due to its reliability good characteristics and performance in addition to the environmental concerns and regulations that restrict the use of lead in nano/microelectronic products. In nano/microelectronics, manufacturing smooth solder coatings free of defects such as voids and cracks, which can compromise joint reliability is crucial. Magnetron sputtering offers a high degree of control over film thickness and composition, resulting in films with excellent uniformity and adhesion. Despite these advantages, fabricating continuous and robust SAC305 films using magnetron sputtering remains a difficult task with limited research …

Cf/Sic Ceramic Matrix Composites With Extraordinary Thermomechanical Properties Up To 2000 °C, Min Sung Park, Jian Gu, Heesoo Lee, Sea Hoon Lee, Lun Feng, William Fahrenholtz

Materials Science and Engineering Faculty Research & Creative Works

The thermomechanical properties of carbon fiber reinforced silicon carbide ceramic matrix composites (Cf/SiC CMCs) were studied up to 2000 °C using high temperature in situ flexural testing in argon. The CMC specimens were fabricated using an ultrahigh concentration (66 vol%) aqueous slurry containing nano-sized silicon carbide powder. The SiC powder compacts were obtained by drying the slurry and were densified using the precursor impregnation and pyrolysis (PIP) method with field assisted sintering technology/spark plasma sintering (FAST/SPS). The high relative density of the SiC green body (77.6%) enabled densification within 2.5 days using four PIP cycles. In contrast, conventional PIP processes …

Phosphate-Based Dechlorination Of Electrorefiner Salt Waste Using A Phosphoric Acid Precursor, Paige Murray, Harmony Werth, Sean Sullivan, Brian J. Riley, Michael Simpson, Charmayne E. Lonergan, Krista Carlson

Materials Science and Engineering Faculty Research & Creative Works

Electrochemical processing of spent nuclear fuel in molten chloride salts results in radioactive salt waste. Chlorine removal from the salt has been identified as an effective and efficient first step in the management of high-level waste. In this work, a simple salt was dechlorinated with a phosphoric acid phosphate precursor, resulting in a glassy dechlorinated product. The dechlorination efficacy was evaluated in air and argon environments. This work serves as an initial step to advance the technological readiness level of h3po4-based dechlorination step toward implementation of iron phosphate waste forms to immobilize electrochemical fuel reprocessing salt waste streams.

Thermal And Electrical Properties Of Single-Phase High Entropy Carbide Ceramics, Paul M. Brune, Gregory E. Hilmas, William G. Fahrenholtz, Jeremy Lee Watts, Stefano Curtarolo

Materials Science and Engineering Faculty Research & Creative Works

Thermal and Electrical Properties Were Investigated for Five Nominally Phase-Pure High Entropy Carbide Ceramics. the Compositions (Hf0.2Nb0.2Ta0.2Ti0.2Zr0.2)C, (Cr0.2Hf0.2Ta0.2Ti0.2Zr0.2)C, (Hf0.2Mo0.2Ta0.2Ti0.2Zr0.2)C, (Hf0.2Ta0.2Ti0.2W0.2Zr0.2)C, and (Hf0.2Mo0.2Ti0.2W0.2Zr0.2)C Were Synthesized by Carbothermal Reduction of Oxides. the Thermal Diffusivity and Heat Capacity Were Measured from Room Temperature to 1800°C. the Room Temperature Thermal Conductivity Ranged from 5.1 W/mK for (Hf0.2Mo0.2Ti0.2W0.2Zr0.2)C to 9.0 W/mK for (Cr0.2Hf0.2Ta0.2Ti0.2Zr0.2)C. the Thermal Conductivity Increased over the Temperature Range with Maximum Conductivities of 19.6 W/mK Measured for (Hf0.2Mo0.2Ta0.2Ti0.2Zr0.2)C to 29.7 W/mK for (Cr0.2Hf0.2Ta0.2Ti0.2Zr0.2)C at 1800°C. the Electron Contribution to Thermal Conductivity Calculated from Measured Electrical Resistivity Varied from 41% to 52% of the …

Pressureless Sintering And Properties Of Additively Manufactured Zrb2–Sic, Marharyta Lakusta, Nicholas M. Timme, Jeremy L. Watts, William G. Fahrenholtz, Gregory E. Hilmas, David W. Lipke

Materials Science and Engineering Faculty Research & Creative Works

Densification behavior, grain growth kinetics, mechanical and thermal properties of pressurelessly sintered zirconium diboride–silicon carbide (ZrB2–SiC) fabricated by extrusion of high solids loading pastes have been studied. The effects of sintering temperature (1600–2300°C), heating rate during constant heating rate sintering (10–50°C/min), and time during isothermal sintering (3–24 h) on density and grain size were examined. The apparent activation energy for densification was determined to be 940 ± 90 kJ/mol, suggesting lattice diffusion as the dominant sintering mechanism. Grain growth of both ZrB2 and SiC followed a normal grain growth power law with grain growth exponent n = 2 indicating diffusion-controlled …

A Concept Of Producing Aluminum In-Situ On The Moon Through Molten Salt Electrolysis, Jacob N. Ortega, Jeffrey Smith, Fateme Rezaei, David Bayless, William Schonberg, Daniel Stutts, Daoru Han

Materials Science and Engineering Faculty Research & Creative Works

This paper presents a concept of producing aluminum in-situ on the lunar surface, namely, the Lunar In-Situ Aluminum Production through Molten Salt Electrolysis (LISAP-MSE) method developed at Missouri University of Science and Technology. This paper aims to demonstrate the use of electro-deoxidation to reduce aluminum oxide (i.e., alumina) into aluminum and oxygen gas via electrolysis in a molten salt bath for the production of aluminum on the Moon. It is shown that with a steady supply of hydrogen chloride, this in-situ resource utilization (ISRU) method could supply several necessary materials consumed in the electro-deoxidation process except hydrogen chloride to produce …

The Development Of Hard Materials And Fibrous Monolith Composites For Friction Stir Welding, Paul Michael Brune

Doctoral Dissertations

"This research focuses on the development of hard materials and fibrous monolith composites for the purpose of adding to current friction stir welding tool technology. Well studied hard material systems, such as WC-Co, were incorporated and evaluated as cell materials for fibrous monolith composites with ductile cell boundaries of Co, W, and Mo. The indentation behavior of the WC-Co and WC-Co-cBN composites indicated possible crack deflection at the cell/cell boundary interface. Cylindrical pin friction stir welding tools were developed for each of the three fibrous monolith material systems. Welding was achieved on AA1100 aluminum, 260 brass, and AISI 1018 steel …

Production Of Glass-To-Metal Seals Using Additive Manufacturing Techniques, Aaron Read

Masters Theses

"Glass-to-metal (GtM) seals are hermetic barriers between glass and metal components, often used in the electronic and vacuum industries. Creating the seals traditionally requires heating all the components to the glass melting temperature, where the glass will flow and bond to the metal. Due to the manufacturing constraints of the individual components and sealing conditions there are geometric and material restrictions. Additive manufacturing techniques were used to make GtM seals to reduce these restrictions.

Hermetic, single pin seals were produced using printed metal shells, by selective laser melting (SLM), and digital light processing (DLP) printed glass preforms. Glass preforms were …

Processing & Properties Of Zirconium Carbide Manufactured By Ceramic On-Demand Extrusion, Clare Sabata

Masters Theses

"This research focuses on the development of a zirconium carbide (ZrC) paste for use in material extrusion direct ink write additive manufacturing (AM) followed by the pressure less densification of ZrC and the mechanical and thermal characterization of the resulting ceramics. A highly loaded, aqueous paste was developed using commercial ZrC powder ball milled to ~1 μm. Optimal dispersant, binder, and solids loading were found by rheological characterization. The paste composition consisted of 46-47 vol% ZrC, 43.5 vol% distilled water, 8.1 vol% dispersant, and 1.6 vol% binder. A yield stress of ~8 Pa allowed for shape retention upon removal of …

Ltspice Modeling For Gan-Git Hemt Including Cryogenic Temperature, Md Maksudul Hossain, Yuqi Wei, H. Alan Mantooth

Electrical Engineering Faculty Publications and Presentations

Highly efficient electrically driven avionics have led to a renewed interest in cryogenic propulsion systems with the goal of reducing carbon emission footprint. Although cryogenic converters promise better efficiency and improved power density, the successful design is incumbent upon the appropriate switching device selection and simulation-based analyses prior to initial prototyping. In this work, a datasheet-driven compact model for a gallium nitride (GaN) Gate Injection Transistor (GIT) has been proposed and implemented in LTspice, a versatile, high performance, and free circuit simulator in order to investigate the merit of the chosen device in a power electronic system.

In-Depth Characterization Of The Selective Oxidation Products Of Hafnium Carbide, Jonathan Allen Scott

Doctoral Dissertations

"Materials capable of withstanding oxidative environments at temperatures >2000°C are necessary for hypersonic applications. Hafnium carbide (HfC) shows a combination of properties that lends itself toward these applications; however, its oxidation behavior is poorly understood. At 1300°C, HfC was found to oxidize via the following mechanism: 1) Initial oxidation of both C and Hf present in the system, 2) Formation of an interconnected pore network, whose size is related to the volume of gases being generated during the oxidation process, 3) Growth of the oxide scale to become sufficiently protective, 4) Formation of an initially amorphous “HfO₂C” at …

Solvent-Free Manufacturing Of Lithium-Ion Battery Electrodes Via Cold Plasma, Zhiming Liang, Tianyi Li, Holden Chi, Joseph Ziegelbauer, Kai Sun, Ming Wang, Wei Zhang, Tuo Liu, Yang-Tse Cheng, Zonghai Chen, Xiaohong Gayden, Chunmei Ban

Chemical and Materials Engineering Faculty Publications

Slurry casting has been used to fabricate lithium-ion battery electrodes for decades, which involves toxic and expensive organic solvents followed by high-cost vacuum drying and electrode calendering. This work presents a new manufacturing method using a nonthermal plasma to create inter- particle binding without using any polymeric binding materials, enabling solvent-free manufacturing electrodes with any electrochemistry of choice. The cold-plasma-coating technique enables fabricating electrodes with thickness (>200 lm), high mass loading (>30 mg cm^-2), high peel strength, and the ability to print lithium-ion batteries in an arbitrary geometry. This crosscutting, chemistry agnostic, platform technology would increase energy density, …

Effect Of Resin Bleed Out On Compaction Behavior Of The Fiber Tow Gap Region During Automated Fiber Placement Manufacturing, Von Clyde Jamora, Virginia Rauch, Sergii G. Kravchenko, Oleksandr G. Kravchenko

Mechanical & Aerospace Engineering Faculty Publications

Automated fiber placement is a state-of-the-art manufacturing method which allows for precise control over layup design. However, AFP results in irregular morphology due to fiber tow deposition induced features such as tow gaps and overlaps. Factors such as the squeeze flow and resin bleed out, combined with large non-linear deformation, lead to morphological variability. To understand these complex interacting phenomena, a coupled multiphysics finite element framework was developed to simulate the compaction behavior around fiber tow gap regions, which consists of coupled chemo-rheological and flow-compaction analysis. The compaction analysis incorporated a visco-hyperelastic constitutive model with anisotropic tensorial prepreg viscosity, which …

Effect Of Post-Cured Through Thickness Reinforcement On Disbonding Behavior In Skin-Stringer Configuration, Jimesh D. Bhagatji, Christopher Morris, Yogaraja Sridhar, Bodhisatwa Bhattacharjee, Krishnanand N. Kaipa, Oleksandr G. Kravchenko

Mechanical & Aerospace Engineering Faculty Publications

An experimental investigation of interlaminar toughness for post-cured through-thickness reinforcement (PTTR) skin-stringer sub-element is presented. The improvement in the crack resistance capability of skin-stringer samples was shown through experimental testing and finite element analysis (FEA) modeling. The performance of PTTR was evaluated on a pristine and initial-disbond of the skin-stringer specimen. A macro-scale pin-spring modeling approach was employed in FEA using a non-linear spring to capture the pin failure under the mixed-mode load. The experimental results showed a 15.5% and 20.9% increase in strength for the pristine-PTTR and initial-disbond PTTR specimens, respectively. The modeling approach accurately represents the overall structural …