Structures and Materials Commons^™

Predicting Flexural Strength Of Composite Honeycomb Core Sandwich Panels Using Mechanical Models Of Face Sheet Compressive Strength, Nicholas Bruffey, William Shiu

Materials Engineering

The design process at Zodiac Aerospace requires the ability to accurately predict the strength of a composite honeycomb core sandwich panel to adhere to strict FAA regulations. The most common failure mode in long beam composites is in compression. Following ASTM D7249 for a four-point bend test of a long beam flexural test, a mechanical model has been developed that relates the compressive strength of glass fiber face sheets to the flexural strength of the sandwich panel. Zodiac does not currently have data on the compressive strength of the face sheets, so testing was performed to find this property. Asymmetric …

Controlling Grain Size In Cold Worked And Annealed 1100 Aluminum To Optimize Ductility In Rocket Diaphragm Systems, Ryan Lewis, Bryce Simmons, Jessica Williams

Materials Engineering

Liquid propellant rocket diaphragms require extreme ductility. 1100 Aluminum is used for its high ductility, but the post-processing cold work and subsequent anneal result in excessively large grains. The effect of heat treatment and cold work on grain size in 1100 aluminum was explored. The samples were cold worked to 0, 5, 10, 15 and 30% using tensile elongation. The samples were then heat treated per AMS 2770 with either a "Steel Conduction" (1000 – 1150°F/min) or a "Production" (16 – 18°F/min) heating rate. The grain size of the samples were measured using the mean lineal intercept method. The grain …

Design, Manufacture, Dynamic Testing, And Finite Element Analysis Of A Composite 6u Cubesat, Yanina Soledad Hallak

Master's Theses

CubeSats, specially the 6U standard, is nowadays the tendency where many developers point towards. The upscaling size of the standard and payloads entail the increase of the satellite overall mass. Composite materials have demonstrated the ability to fulfill expectations like reducing structural masses, having been applied to different types of spacecraft, including small satellites.

This Thesis is focused on designing, manufacturing, and dynamic testing of a 6U CubeSat made of carbon fiber, fiberglass, and aluminum.

The main objective of this study was obtaining a mass reduction of a 6U CubeSat structure, maintaining the stiffness and strength. Considering the thermal effects …

Improving Damage Tolerance Of Composite Sandwich Structures Subjected To Low Velocity Impact Loading: Experimental And Numerical Analysis, Ravi B. Gondaliya

Doctoral Dissertations and Master's Theses

Sandwich structures with composite facing skins have seen applications in variety of sectors including aerospace and automobile, owing to their high specific mechanical properties. However, there is a need to develop better damage tolerant sandwich structures since conventional composite facing skins exhibit low impact resistance in the transverse direction. Here, composite skin sandwich structures with three different impact resistant core materials were fabricated and tested both experimentally and numerically. Neat CFRP and 2024-T3 aluminum alloy sheets were also investigated. Cores utilizing impact resistant D3O® were found to have very favorable weight specific energy absorbing properties at higher impact velocities as …

Effects Of Curing Cycle And Loading Rates On The Bearing Stress Of Double Shear Composite Joints, Mateja Andrejic

Master's Theses

In the last few decades, there has been a shift to using more lightweight materials for the potential of fuel consumption reduction. In the Aerospace Industry, conventional metal structures are being replaced by advanced composite structures. The major advantage of an advanced composite structure is the huge reduction in the number of parts and joints required. Also composite materials provide better resistance to creep, corrosion, and fatigue. However, one cannot eliminate all the joints and attachments in an aircraft’s structure. Eliminating structural joints is impractical in present-day aircraft because of the requirements for inspection, manufacturing breaks, assembly and equipment access, …

Effects Of Additive Manufacturing Methods On The Dynamic Properties Of 15-5ph Stainless Steel, Allison A. Dempsey

Theses and Dissertations

Experimental research was conducted to determine the dynamic properties and characterize the microstructure of 15-5PH Stainless Steel manufactured through Direct Metal Laser Sintering (DMLS) additive manufacturing (AM) processes and heat treated using common heat treatment protocols. A thorough understanding of the material's properties is necessary before such parts are utilized in an operational capacity. Of the five builds, two deviated significantly from the specified composition of 15-5PH stainless steel. The remaining three builds, possessing the desired composition and crystalline structure, were tested in compression and tension at two strain rates. Tension tests using a reflected wave and a momentum trap …

Fatigue Behavior Of An Advanced Sic/Sic Composite At 1300° C In Air And Steam, Michael D. Lee

Theses and Dissertations

The fatigue behavior of an advanced silicon carbide/silicon carbide (SiC/SiC) ceramic matrix composite (CMC) was investigated at 1300 ºC in laboratory air and in steam environments. The composite was manufactured using chemical vapor infiltration (CVI). The composite consisted of an oxidation-inhibited matrix, which was comprised of alternating layers of silicon carbide and boron carbide and was reinforced with laminated Hi-Nicalon™ fibers woven in a plain weave. Fiber preforms had pyrolytic carbon fiber coating with boron carbon overlay applied. Two specimen geometries were evaluated, a dog bone and an hourglass geometry. Tensile stress-strain behavior and tensile properties were evaluated at 1300 …

Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 700°C In Air And In Silicic Acid-Saturated Steam, Matthew W. Piper

Theses and Dissertations

Aircraft structural and engine components are subjected to elevated temperature and steam environments during operation. Turbine blades experience particularly harsh conditions that are approaching the operating temperature limits of current Nickel-based superalloys even with active cooling. Ceramic matrix composites (CMCs), which demonstrate high specific strength and specific stiffness and maintain these properties at elevated temperatures such that active cooling is not required, are prime candidates to replace superalloys as the materials for turbine blades. Ceramic matrix composites are composite materials that consist of a ceramic matrix with fiber reinforcement. This research investigated a silicon carbide (SiC) fiber, Hi-Nicalon™ S, which …

Effect Of Low Velocity Impact On The Vibrational Behavior Of A Composite Wing, Richard M. De Luna

Master's Theses

Impact strength is one of the most important structural properties for a designer to consider, but it is often the most difficult to quantify or measure. A major concern for composite structures in the field is the effect of foreign objects striking composites because the damage is often undetectable by visual inspection. The objective for this study was to determine the effectiveness of using dynamic testing to identify the existence of damage in a small scale composite wing design. Four different impact locations were tested with three specimens per location for a total of 12 wings manufactured. The different impact …

Thermal Transport Properties Of Dry Spun Carbon Nanotube Sheets, Heath E. Misak, James L. Rutledge, Eric D. Swenson, Shankar Mall

Faculty Publications

The thermal properties of carbon nanotube- (CNT-) sheet were explored and compared to copper in this study. The CNT-sheet was made from dry spinning CNTs into a nonwoven sheet. This nonwoven CNT-sheet has anisotropic properties in in-plane and out-of-plane directions. The in-plane direction has much higher thermal conductivity than the out-of-plane direction. The in-plane thermal conductivity was found by thermal flash analysis, and the out-of-plane thermal conductivity was found by a hot disk method. The thermal irradiative properties were examined and compared to thermal transport theory. The CNT-sheet was heated in the vacuum and the temperature was measured with an …

Process Monitoring Of Glass Reinforced Polypropylene Laminates Using Fiber Bragg Gratings, M. Mulle, H. Wafai, A. Yudhanto, G. Lubineau, R. Yaldiz, W. Schijve, N. Verghese

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Hot-press molding of glass-fiber-reinforced polypropylene (GFPP) laminates was monitored using longitudinally and transversely embedded fiber Bragg gratings (FBGs) at different locations in unidirectional laminates. The optical sensors proved to efficiently characterize some material properties; for example, strain variations could be related physical change of the laminate, revealing key transition points such as the onset of melt or solidification. These results were confirmed through some comparison with traditional techniques such as differential scanning calorimetry. After the GFPP plate was released from the mold, residual strains were estimated. Because cooling rate is an important process parameter in thermoplastics, affecting crystallinity and ultimately …

Growth Control Of Oxygen Stoichiometry In Homoepitaxial Srtio3 Films By Pulsed Laser Epitaxy In High Vacuum, Ho Nyung Lee, Sung S. Ambrose Seo, Woo Seok Choi, Christopher M. Rouleau

Physics and Astronomy Faculty Publications

In many transition metal oxides, oxygen stoichiometry is one of the most critical parameters that plays a key role in determining the structural, physical, optical, and electrochemical properties of the material. However, controlling the growth to obtain high quality single crystal films having the right oxygen stoichiometry, especially in a high vacuum environment, has been viewed as a challenge. In this work, we show that, through proper control of the plume kinetic energy, stoichiometric crystalline films can be synthesized without generating oxygen defects even in high vacuum. We use a model homoepitaxial system of SrTiO₃ (STO) thin films on …

Characterization Of Dispersion And Residual Stress In Nanoparticle Reinforced Hybrid Carbon Fiber Composites, Alex Selimov

Honors Undergraduate Theses

Hybrid carbon fiber reinforced composites are a new breed of materials that are currently being explored and characterized for next generation aerospace applications. Through the introduction of secondary reinforcements, such as alumina nanoparticles, hybrid properties including improved mechanical properties and stress sensing capabilities can be achieved. In order to maximize these properties, it is necessary to achieve a homogeneous dispersion of particulate filler. Utilizing the photoluminescent properties of alumina, it is possible to compare local levels of particle concentration through emission intensities as a way to determine the effectiveness of the tested manufacturing parameters in increasing material homogeneity. Parameters of …

Cryogenic Processing Of Al 7050-T7451 Alloy For Improved Surface Integrity, Bo Huang

Theses and Dissertations--Mechanical and Aerospace Engineering

Al 7050-T7451 alloy with good combinations of strength, stress corrosion cracking resistance and toughness, is used broadly in the aerospace/aviation industry for fatigue-critical airframe structural components. However, it is also considered as a highly anisotropic alloy as the crack growth behavior along the short transverse direction is very different from the one in the long transverse direction, due to the inhomogeneous microstructure with the elongated grains distributed in the work material used in the sheet/plate applications. Further processes on these materials are needed to improve its mechanical and material properties and broaden its applications.

The material with ultra-fine or nano …

Constructal Alkaline Membrane Fuel Cell (Amfc) Design, E. M. Sommer, J. V. C. Vargas, Lauber De Souza Martins, J. C. Ordonez

Faculty Publications

This paper introduces a structured procedure to optimize the internal structure (relative sizes, spacing) and external shape (aspect ratios) of a single alkaline membrane fuel cell so that net power is maximized. The optimization of flow geometry is conducted for the smallest (elemental) level of a fuel cell stack, i.e., the single alkaline membrane fuel cell, which is modeled as a unidirectional flow system. The polarization curve, total and net power, and efficiency are obtained as functions of temperature, pressure, electrolyte solution concentration (KOH), geometry and operating parameters. The optimization is subjected to fixed total volume. There are two levels …

Expedient Airfield Runway Repair Using Folded Fiberglass Mat, Christopher Y. Tuan, Willaim C. Dass

Department of Civil and Environmental Engineering: Faculty Publications

For expedient airfield runway repair, the US Air Force has developed a folded fiberglass mat to cover craters repaired with a well-compacted granular base material. The objective of this study was to evaluate the adequacy of using polymer plugs to anchor the mat to a repaired asphalt pavement for heavy aircraft operations. The effort consisted of materials testing, field experiments and analytical modeling. An 89,800-kg (198,000-pound) load cart having the footprint of a single C-5 main gear was pulled on a mat with wheels locked to simulate full braking forces. Anchor bushings were instrumented to measure anchor loads. A simplified …

Distinction In Corrosion Resistance Of Selective Laser Melted Ti-6al-4v Alloy On Different Planes, Nianwei Dai, Laichang Zhang, Junxi Zhang, Xin Zhang, Qingzhao Ni, Yang Chen

Research outputs 2014 to 2021

Electrochemical measurements and microstructural analysis were performed to study the corrosion resistance of different planes of Ti-6Al-4V alloy manufactured by selective laser melting (SLM). The electrochemical results suggest that its XY-plane possesses a better corrosion resistance compared to XZ-plane in 1 M HCl solution, in spite of slight difference in 3.5 wt.% NaCl solution, suggesting that the different planes exhibit more pronounced distinction in corrosion resistance in harsher solution system. The inferior corrosion resistance of XZ-plane is attributed to the presence of more α′ martensite and less β-Ti phase in microstructure for XZ-plane than for XY-plane of the SLM-produced Ti-6Al-4V …

Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 800°C In Air And In Silicic Acid-Saturated Steam, Scott J. Robertson

Theses and Dissertations

A facility was demonstrated that successfully resolved problems highlighted by previous attempts to study SiC fibers in steam. Monotonic tension and creep tests were conducted to characterize the fibers. The tensile strength of the fibers showed little dependence on applied stress rate, indicating a resistance to environmentally assisted crack growth. Climb-controlled diffusion in air and grain boundary sliding in silicic acid-saturated steam were the dominant damage mechanisms. Silicic acid-saturated steam had a degrading effect on the mechanical performance of the fibers, but much less than unsaturated steam environments. The Monkman-Grant relationship was demonstrated for Hi-NicalonTM S fibers and may be …

Polyacrylonitrile Copolymers: Effects Of Molecular Weight, Polydispersity, Composition, And Sequencing On Thermal Ring-Closing Stabilization, Jeremy D. Moskowitz

Dissertations

Controlled polyacrylonitrile (PAN)-based carbon fiber precursors with defined molecular weights, polydispersities, compositions, and architectures have been prepared for their study on thermal ring-closing stabilization behavior. PAN and its copolymers of number average molecular weights exceeding 170,000 g/mol were successfully synthesized via low temperature reversible addition-fragmentation chain transfer (RAFT) polymerization. RAFT polymerizations of PAN-based precursors were compared to conventional free radical solution polymerizations with a focus on the effects of molecular weight and polydispersity on structural evolution and cyclization efficiency. When RAFT polymerization was extended to copolymers, it was found that RAFT copolymers achieved greater cyclization intensities and improved thermal stability …

Low-Velocity Impact Analysis Of Composite Repair Patches Of Different Shapes, Sarvesh Baliga

Doctoral Dissertations and Master's Theses

The area under crack for various structures can be effectively repaired by the use of composite materials. Low velocity impact can cause barely visible damage to the interior structure of laminated composite. These impacts can cause delamination in composite materials. In this study, a Finite Element Analysis was conducted using Abaqus/Explicit and the results of the analysis were compared to the experimental data from literature. E-glass/epoxy composite laminate was subjected to a low velocity impact test. To study the effect of patch repair, a composite patch was applied on a cracked laminate and a low velocity impact was then conducted …

Volatile Condensible Material Deposition In Leo Simulated Environment, Jinya Pu

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Room Temperature Vulcanized (RTV) silicone and compounds are widely used in outer-space for bonding or potting spacecraft components. In geosynchronous equatorial orbit (GEO), the silicone may outgas species which can condense on optically sensitive surfaces and degrade their performance, therefore shortening the lifetime of spacecraft. In low-earth-orbit (LEO), the silicone rubber is subject to an energetic and corrosive environment. Atomic oxygen (AO) and ultraviolet radiation can cause abrasion and degradation of the silicone rubber, cause changes in existing condensed VCM films and affect the properties of VCM films condensing in this atmosphere. Experiments were performed to simulate GEO conditions. In …

Tension-Compression Fatigue Behavior Of 2d And 3d Polymer Matrix Composites At Elevated Temperature, Saleh A. Alnatifat

Theses and Dissertations

In this Research effort, the tension-compression fatigue behavior of the 3D and 2D PMCs with 0/90˚ fiber orientation (newly developed) was investigated. These polymer composites consist of an NRPE (high-temperature polyimide) matrix with carbon fiber reinforcement. Compressive properties were assessed at (1) room temperature and (2) elevated temperature with one side, Tright, at 329˚C and the other side open to the ambient air. Tension-compression fatigue tests were conducted at elevated temperature with a frequency of 1 Hz and a ratio of minimum to maximum stress of -1.

Characterizing Strain Accumulation, Residual Stress, And Microstructure Of Additive Manufactured Materials, Hannah K. Woods, Todd A. Book, Catalina Parada, Michael D. Sangid

The Summer Undergraduate Research Fellowship (SURF) Symposium

Additive Manufacturing (AM) is a rapidly evolving fabrication technology beneficial for its cost-saving potential to produce complex, low-volume shapes. However, AM materials are currently limited to nonstructural applications due to variability in their structural integrity, particularly their fatigue lives. IN718, Ti64, and Al10MgSi specimens manufactured by Direct Metal Laser Sintering (DMLS) were characterized based on variation of post-processing techniques and build direction. To understand the impact of each variable, surface roughness, hardness, residual stresses, microstructure, and strain accumulation in response to Low Cycle Fatigue (LCF) were studied. The use of Electron Backscatter Diffraction (EBSD) provided grain orientation and grain size …

Identifying And Correcting Biases In Digital Image Correlation At Multiple Length Scales, Catalina Parada, Alberto W. Da Silva Mello, Michael D. Sangid, Hannah K. Woods, Samuel E. Otto

The Summer Undergraduate Research Fellowship (SURF) Symposium

Accurate strain measurement at grain and sub-grain levels is important to predict and understand crack initiation during fatigue of materials. During cyclic loading, low magnitude strain is accumulated in the material and any distortion in the images can lead to inaccurate strain measurements and false prediction of the material’s behavior. Digital Image Correlation (DIC) is a reliable tool used to measure strain localization by correlating images before, during, and after cyclic loading. DIC tracks the deformation of nano/micro-scale patterns placed on the surface of the specimens to determine strain fields. However, DIC software does not account for biases due to …

The Robert & Esther Goddard Papers, Robert H. Goddard

Finding Aids

Dr. Robert H. Goddard was a member of the Clark Physics Department for 29 years. Foremost American pioneer of rocket research, he laid the technical and theoretical foundations for many of the developments in long-range rockets, missiles, satellites and space flight, which collectively put us into the Space Age.

The collection includes correspondence, diaries, journals, patent applications and awards, reports, and photographs. The collection also includes original paintings by Dr. Goddard.

Techniques For Payload Stabilization For Improved Photography During Stratospheric Balloon Flights, James Flaten, Christopher Gosch, Joseph (Benjamin) Habeck

2017 Academic High Altitude Conference

Payload-box rotation and swing are perennial challenges to achieving high-quality photography (typically videography) during weather-balloon flights to “near-space” (AKA the stratosphere). Continuous camera motion can lead to blurred still photos, nearly-impossible-to-watch video footage, and precludes time-exposure photography required for most astronomical imaging even though altitudes are reached where the daytime sky appears black. Apparently-random payload rotation, persisting even at altitude, can often exceed servo rotation rates and frustrate attempts to do active camera pointing. Here we discuss mostly-passive payload stabilization strategies we, and our collaborators, have used to mitigate and dampen both swing and rotation of suspended payloads on high-altitude …

Simulation Of Metal Particulates In High Energetic Materials, Eduardo Nieto

Theses and Dissertations

This research focused on analyzing the effects of aluminum in high explosives such as PBX9501 using the MPEXS computational simulation code for a wide range of metalized explosive cases. The varying parameters are aluminum particle diameter and mass fraction of aluminum. The addition of metal particulates in explosive mixtures increases the density of the shock wave, causing a higher pressure in the shock. It was concluded that pressure and density steadily increases as the Al particle diameter increases, and pressure and density decreases when Al mass fraction increases. The concentrated pressures will dissipate quickly due to the high density, providing …

Creep Of Sylramic-Ibn Fiber Tows At Elevated Temperature In Air And In Silicic Acid-Saturated Steam, Kevin B. Sprinkle

Theses and Dissertations

Stressed oxidation experiments on Sylramic-iBN fiber tows were performed to evaluate the novel fiber's mechanical performance, creep behavior, and creep mechanisms. This research effort investigated creep response of Sylramic-iBN fiber tows at elevated temperatures in both air and in silicic acid-saturated steam environments. Creep experiments were conducted at creep stresses ranging from 127 to 762 MPa at 400°C and 500°C in order to examine the mechanical behavior of the Sylramic-iBN fiber tows at temperatures below and above the melting point of boria (450°C). Sylramic-iBN fibers are known to have excellent creep resistance, better than most other non-oxide fibers and significantly …

Effect Of Prior Exposure At Elevated Temperatures On Tensile Properties And Stress-Strain Behavior Of Four Non-Oxide Ceramic Matrix Composites, Sarah M. Wallentine

Theses and Dissertations

Thermal stability of four non-oxide ceramic matrix composites was studied. The materials studied were commercially available composites: SiC/SiNC; C/SiC; C/SiC-B4C (C/HYPR-SiC^TM); and SiC/SiC-B4C (SiC/HYPR-SiC^TM). COI Ceramics manufactured the SiC/SiNC and C/SiC composites using polymer infiltration and pyrolysis (PIP). The C/HYPR-SiC^TM and SiC/HYPR-SiC^TM CMCs were manufactured by Hyper-Therm High-Temperature Composites using chemical vapor infiltration (CVI). All four composites rely on a dense matrix for strength, stiffness, and oxidation protection. Fiber coating provides a fiber-matrix interface that allows fiber-matrix debonding and fiber pullout to occur, imparting fracture toughness to the CMC. The SiC/SiNC, C/SiC, and C/HYPR-SiC …

Automatic Building Change Detection In Wide Area Surveillance, Paheding Sidike, Almabrok Essa, Fatema Albalooshi, Vijayan K. Asari, Varun Santhaseelan

Electrical and Computer Engineering Faculty Publications

We present an automated mechanism that can detect and characterize the building changes by analyzing airborne or satellite imagery.

The proposed framework can be categorized into three stages: building detection, boundary extraction and change identification. To detect the buildings, we utilize local phase and local amplitude from monogenic signal to extract building features for addressing issues of varying illumination. Then a support vector machine with Radial basis kernel is used for classification. In the boundary extraction stage, a level-set function with self-organizing map based segmentation method is used to find the building boundary and compute physical area of the building …