Creasing Of Polyimide Thin Film For Use In Solar Sails,
2021
University of Central Florida
Creasing Of Polyimide Thin Film For Use In Solar Sails, Andrew Allen
Electronic Theses and Dissertations, 2020-2023
Polymer thin membranes are used in a variety of deployable structures that require large areas and compact stowage. Packaging membrane structures often involves creasing the membrane along predefined fold lines to enforce the desired kinematics under folding action. Inducing permanent deformation by folding to a high curvature is a common method to create creases, particularly in the design of solar sails. The distinct mechanical characteristics at the crease regions have a profound effect on the subsequent deployment and tensioning of the membrane structures. The mechanical and geometric properties at the crease are related to the crease formation process, but the …
Creep Behavior And Deformation Mechanisms Of Spark Plasma Sintered Oxide Ceramics For Aerospace Systems At 1300˚C - 1400˚C,
2021
Air Force Institute of Technology
Creep Behavior And Deformation Mechanisms Of Spark Plasma Sintered Oxide Ceramics For Aerospace Systems At 1300˚C - 1400˚C, David D. Swanson
Theses and Dissertations
The mechanical behavior of YAG and LuAG was investigated at elevated temperatures. The specific materials investigated in this work include high-purity, polycrystalline YAG, high-purity, polycrystalline LuAG, and two doped variants of YAG: 2at% Yb-doped, polycrystalline YAG and 2at% Er-doped, polycrystalline YAG. Several billets of each material were prepared and processed by means of spark plasma sintering (SPS). Many different sintering parameters were utilized in order to obtain materials with various physical properties and to identify the effects of sintering parameters on the average grain size of the resulting materials. The compressive creep behavior of these materials was investigated at 1300°C …
Fabrication & Mechanical Properties Of Hastelloy-X Matrix Ceramic Composite,
2021
Embry-Riddle Aeronautical University
Fabrication & Mechanical Properties Of Hastelloy-X Matrix Ceramic Composite, Sultan Stewart
Doctoral Dissertations and Master's Theses
In the aerospace industry, there is a desire for increased thermal and mechanical properties of sealing materials. In this thesis, porous Hastelloy-X alloy scaffolds with 80% porosity, currently used for fabricating seals in turbine applications, were used as the base material. The microstructure of the porous Hastelloy-X scaffolds was infiltrated using a room temperature curing silicate colloid (trade name -Dichtol HTWG Hydro #2506) and a novel zirconia based colloid to fabricate the metal matrix composites. Various fabrication processes, some using vacuum and pressure to assist the flow were utilized to infiltrate the scaffolds. The green composites were then cured at …
The Effect Of Part Curvature On The Formation Of Residual Stresses In Carbon Fiber Prepreg Laminates,
2021
Embry-Riddle Aeronautical University
The Effect Of Part Curvature On The Formation Of Residual Stresses In Carbon Fiber Prepreg Laminates, Bradley Rogan
Doctoral Dissertations and Master's Theses
The formation of residual stresses during the processing of composite parts can lead to undesired defects such as delamination which can reduce the overall strength of a completed component. Furthermore, the addition of curvature to the part geometry tends to result in wrinkle formation which leads to stress concentrations developing throughout the curing process in the areas near these wrinkles. In this work, Digital Image Correlation (DIC) will be used to monitor the development of stresses throughout the cure cycle of carbon fiber prepreg in several different lay-ups and across tool plates with varying curvatures to determine what effect the …
Mechanical Interfacial Locking And Multiscale Modeling Of Reinforced Thermoplastic Composites For Structural Applications,
2021
Clemson University
Mechanical Interfacial Locking And Multiscale Modeling Of Reinforced Thermoplastic Composites For Structural Applications, Anmol Kothari
All Dissertations
The ever-growing pressure of reducing the adverse impact of transportation systems on environment has pushed industries towards fuel-efficient and sustainable solutions. While several approaches have been used to improve fuel efficiency, the light-weighting of structural components has proven broadly effective. In this regard, reinforced thermoplastic composites (RTPC), owing to their high recyclability, higher impact strength and fast cycle times, have become competitive candidates at an industrial scale. However, to implement RTPC toward large scale structural applications several challenges pertaining to material design and manufacturing effects need to be addressed. To this end, a computational study is carried out to address …
Data-Driven Damage Initiation Criteria For Carbon Fiber Reinforced Polymer Composites,
2021
DePaul University
Data-Driven Damage Initiation Criteria For Carbon Fiber Reinforced Polymer Composites, Alexander Richard Post
College of Computing and Digital Media Dissertations
Computational progressive failure analysis (PFA) is vital for the design, verification, and validation of carbon fiber reinforced polymer (CFRP) composites. However, the computational cost of PFA is usually high due to the complexity of the model. The damage initiation criterion is one of the essential components of a PFA code to determine the transition of a material’s state from pristine or microscopically damaged to macroscopically damaged. In this thesis, data-driven models are developed to determine the matrix damage initiation based on the Mohr-Coulomb model and Hashin model. For 2D plane stress states, the computational cost for determining damage initiation can …
Fatigue Damage Quantification And Life Estimation With Provision For Microstructure,
2021
Louisiana State University
Fatigue Damage Quantification And Life Estimation With Provision For Microstructure, Arash Pourbagheri Jirandehi
LSU Doctoral Dissertations
This dissertation provides methodologies for the quantification of different forms of fatigue damage by considering the role of microstructure. The laws of thermodynamics in conjunction with Finite Element Method (FEM) are utilized to devise thermodynamically-base frameworks for the estimation of cyclic damage in polycrystalline metals. Accordingly, a microstructure-sensitive platform for fatigue life estimation is introduced. The proposed framework is assessed for 3D printed metallic alloys at room and elevated temperatures. Further, it is used to analyze the fatigue performance difference between additively manufactured Inconel 718 in three print orientations. This research is of fundamental vital interest because it ensures that …
Flexible Mold For Microstructures Replication,
2021
Embry-Riddle Aeronautical University
Flexible Mold For Microstructures Replication, Zefu Ren, Dae Won Kim
Student Works
Space debris has been a growing concern in space exploration sector. To combat this issue, biomimicry is utilized to create a gecko’s feet microstructure that will be attached to a gripper or robotic arm. This will enable capture of debris through the use of dry adhesive microstructure. However, the production of such microstructures is expensive which hinders their implementation. The objective of this research is to develop an advanced fabrication process to mass produce gecko’s feet microstructure with soft polymer mold. The possibility of using different coating methods with coating materials will be justified. The process of fabricating mold and …
Evaluation Of Additively Manufactured Lattices Under High Strain Rate Impact,
2021
Air Force Institute of Technology
Evaluation Of Additively Manufactured Lattices Under High Strain Rate Impact, Derek G. Spear
Theses and Dissertations
Several additively manufactured lattice designs and configurations were evaluated under compression loads under various strain rates from quasi-static to highly dynamic. These experiments examined how the mechanical behavior of the lattice changed based on the lattice design properties and the applied strain rates. The modulus of elasticity, yield strength, plateau stress, and toughness were observed to decrease with an increase in strain rate, revealing that the lattice designs exhibit a negative strain rate sensitivity. A new lattice flow stress model was developed to account for the mechanical response of the lattice and was incorporated into a computational model for simulation. …
Radiation Effects On Space Solar Cells At Various Earth And Jupiter Orbital Altitudes,
2021
Purdue University
Radiation Effects On Space Solar Cells At Various Earth And Jupiter Orbital Altitudes, Naazneen Rana
Discovery Undergraduate Interdisciplinary Research Internship
Solar cells are used as the primary power source for earth-orbiting satellites and as a primary/secondary power source for various missions within the solar system. However, high energy particles from the sun, planetary magnetospheres, and the galaxy can affect the performance and life expectancy of the space solar cell and associated power systems. As the interests for interplanetary travel and the exploration of planets within our solar system increase, the need to understand a device’s performance within a particular planet’s environment is necessary. Therefore, this study will analyze the performance of space solar cells, particularly the SolAero IMM-α, at various …
Shape Optimization Of A Sandwich Composite Plate With Low-Velocity Impact Loading And Effect Of Finite Difference Sensitivity Analysis,
2021
Embry-Riddle Aeronautical University
Shape Optimization Of A Sandwich Composite Plate With Low-Velocity Impact Loading And Effect Of Finite Difference Sensitivity Analysis, Utsav Shah
Doctoral Dissertations and Master's Theses
The structural design of spacesuits is essential in an advancing future of both Lunar and Martian space exploration. A typical spacesuit is made of sandwich composite material and designed to withstand various pressure and loading conditions while also considering the safety and comfort of the astronauts. One of the critical load cases in spacesuit design is a low-velocity impact (LVI) which may occur due to tool drop and other similar scenarios. The objectives of this work were (a) to create a finite element (FE) model of a component of a spacesuit, (b) validation of the FE model through experiments, (c) …
Design, Analysis And Experimental Evaluation Of 3d Printed Variable Stiffness Structures,
2021
Embry-Riddle Aeronautical University
Design, Analysis And Experimental Evaluation Of 3d Printed Variable Stiffness Structures, Rossana R. Fernandes
Doctoral Dissertations and Master's Theses
The rapid progress of additive manufacturing (AM) introduces new opportunities but also new challenges for design and optimization to ensure manufacturability, testability and accurate representation/prediction of the models. The present dissertation builds a bridge between design, optimization, AM, testing and simulation of advanced optimized variable-stiffness structures. The first part offers an insight on the mechanical, viscoelastic and failure characteristics of AM continuous fiber composites. This understanding was used in the second part to investigate the feasibility of different topology and fiber-orientation optimization methods and the manufacturability of the resulting models. The study also assesses the effects of the manufacturing constraints …
Fully Coupled Internal Radiative Heat Transfer For The 3d Material Response Of Heat Shield,
2021
University of Kentucky
Fully Coupled Internal Radiative Heat Transfer For The 3d Material Response Of Heat Shield, Raghava S. C. Davuluri, Rui Fu, Kaveh A. Tagavi, Alexandre Martin
Mechanical Engineering Faculty Publications
The radiative transfer equation (RTE) is strongly coupled to the material response code KATS. A P-1 approximation model of RTE is used to account for radiation heat transfer within the material. First, the verification of the RTE model is performed by comparing the numerical and analytical solutions. Next, the coupling scheme is validated by comparing the temperature profiles of pure conduction and conduction coupled with radiative emission. The validation study is conducted on Marschall et al. cases (radiant heating, arc-jet heating, and space shuttle entry), 3D Block, 2D IsoQ sample, and Stardust Return Capsule. The validation results agree well for …
Review: Factors Affecting Composite Laminates Against Lightning Strikes,
2021
CUNY New York City College of Technology
Review: Factors Affecting Composite Laminates Against Lightning Strikes, Aaryan Manoj Nair
Publications and Research
Lightning strike protection (LSP) have recently been a newly developing field particularly with the emergence of graphene thin film integration into carbon fiber composite structures. This technology has a widespread application in airplanes, wind turbines, and other instruments which are susceptible to frequent lightning strikes. Electrical discharge of the instrument in a safe manner is vital for the safety of the passengers (in the case of flights) as well as the integrity of the aircraft structures because of their specific mechanical and structural properties, which are essential for their functioning. The purpose of the study is to fabricate graphene thin …
Additively Manufactured Dielectric Elastomer Actuators: Development And Performance Enhancement,
2021
Embry-Riddle Aeronautical University
Additively Manufactured Dielectric Elastomer Actuators: Development And Performance Enhancement, Stanislav Sikulskyi
Doctoral Dissertations and Master's Theses
The recently emerging and actively growing areas of soft robotics and morphing structures promise endless opportunities in a wide range of engineering fields, including biomedical, industrial, and aerospace. Soft actuators and sensors are essential components of any soft robot or morphing structure. Among the utilized materials, dielectric elastomers (DEs) are intrinsically compliant, high energy density polymers with fast and reversible electromechanical response. Additionally, the electrically driven work principle allows DEs to be distributed in a desired fashion and function locally with minimum interference. Thus, a great effort is being made towards utilizing additive manufacturing (AM) technologies to fully realize the …
Fluid-Structure Interaction Of Nrel 5-Mw Wind Turbine,
2021
The American University in Cairo AUC
Fluid-Structure Interaction Of Nrel 5-Mw Wind Turbine, Mohamed Sayed Elkady Abd-Elhay
Theses and Dissertations
Wind energy is considered one of the major sources of renewable energy. Nowadays, wind turbine blades could exceed 100 m to maximize the generated power and minimize produced energy cost. Due to the enormous size of the wind turbines, the blades are subjected to failure by aerodynamics loads or instability issues. Also, the gravitational and centrifugal loads affect the wind turbine design because of the huge mass of the blades. Accordingly, wind turbine simulation became efficient in blade design to reduce the cost of its manufacturing. The fluid-structure interaction (FSI) is considered an effective way to study the turbine's behavior …
Metallurgical And Thermal Processing Investigation Of Additively Manufactured Superalloys Jbk-75 And Nasa-Hr-1,
2021
California Polytechnic State University, San Luis Obispo
Metallurgical And Thermal Processing Investigation Of Additively Manufactured Superalloys Jbk-75 And Nasa-Hr-1, Allyse Birken, Derek Noel
Materials Engineering
Aerojet Rocketdyne is investigating the use of directed energy deposition (DED), an additive manufacturing process, to reduce cost and lead time for manufacturing complex rocket engine components for their RS-25 engines. JBK-75 and NASA-HR-1, two Fe-Ni-base, age-hardenable (γ′) superalloys, are used for nozzle structural jackets and hot gas manifolds. Currently, these parts are produced using traditional forging or casting methods followed by intensive machining operations. Additionally, these alloys were designed for use in the wrought condition and require a different set of post-processing heat treatments when produced using DED due to their dendritic, segregated microstructure in the as-built condition. Homogenization …
Space Suit Attachment Quick Release System,
2021
California Polytechnic State University, San Luis Obispo
Space Suit Attachment Quick Release System, Elyse C. Gillis-Smith, Andres I. Elzaurdia, Cole H. Stanton, Michael T. Roth
Mechanical Engineering
NASA plans to make it back to the Moon by 2024 with their Artemis Program, and stay there for a longer period of time to conduct research which will support the future of space exploration. While on the lunar surface, astronauts need to maximize their efficiency by carrying tools on their Exploration Extravehicular Mobility Unit (xEMU), and to accommodate this need, the Extravehicular Activity (EVA) Tools Team is pursuing a utility belt concept. The objective of this project is to develop a system capable of interfacing between the utility belt and any given tool, while also accommodating numerous restrictions and …
Prediction Of In-Plane Stiffnesses And Thermomechanical Stresses In Cylindrical Composite Cross-Sections,
2021
California Polytechnic State University, San Luis Obispo
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 …
Effect Of Galvanic Corrosion On Crack Propagation Of Cold Expanded Holes In Aa2024-T3,
2021
Embry-Riddle Aeronautical University
Effect Of Galvanic Corrosion On Crack Propagation Of Cold Expanded Holes In Aa2024-T3, Ken Shishino
Doctoral Dissertations and Master's Theses
A search for the balance between weight reduction and durability of a structure has always been a popular topic within the aerospace industry. Among numerous researches to improve a structure’s fatigue life, processes on mechanically fastened joints have been a topic of focus as it is naturally a discontinuity in the material leading to a local stress concentration under loading. Cold expansion is a well-known technique with a wide range of applications in both new and repaired structures. The benefits include the extension of fatigue life and a delay in crack growth without addition of weight. However, localized galvanic corrosion …
