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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Stability Analysis of Intertank Formed Skin/Stringer Compression Panel with Simulated Damage

The External Tank (ET) is a component of the Space Shuttle launch vehicle that contains fuel and oxidizer. During launch, the ET supplies the space shuttle main engines with liquid hydrogen and liquid oxygen. In addition to supplying fuel and oxidizer, it is the backbone structural component of the Space Shuttle. It is comprised of a liquid hydrogen (LH2) tank and a liquid oxygen (LOX) tank, which are separated by an Intertank. The Intertank is a stringer-stiffened cylindrical structure with hat-section stringers that are roll formed from aluminum-lithium alloy Al-2090. Cracks in the Intertank stringers of the STS-133 ET were noticed after a November 5, 2010 launch attempt. The cracks were approximately nine inches long and occurred on the forward end of the Intertank (near the LOX tank), along the fastener line, and were believed to have occurred while loading the ET with the cryogenic propellants. These cracks generated questions about the structural integrity of the Intertank. In order to determine the structural capability of the Intertank with varying degrees of damage, a finite element model (FEM) simulating a 1995 compression panel test was analyzed and correlated to test data. Varying degrees of damage were simulated in the FEM, and non-linear stability analyses were performed. The high degree of similarity between the compression panel and the Intertank provided confidence that the ET Intertank would have similar capabilities.

Harper, David W.↗
NASA NTRS2012

Design, Optimization, and Evaluation of A1-2139 Compression Panel with Integral T-Stiffeners

A T-stiffened panel was designed and optimized for minimum mass subjected to constraints on buckling load, yielding, and crippling or local stiffener failure using a new analysis and design tool named EBF3PanelOpt. The panel was designed for a compression loading configuration, a realistic load case for a typical aircraft skin-stiffened panel. The panel was integrally machined from 2139 aluminum alloy plate and was tested in compression. The panel was loaded beyond buckling and strains and out-of-plane displacements were extracted from 36 strain gages and one linear variable displacement transducer. A digital photogrammetric system was used to obtain full field displacements and strains on the smooth (unstiffened) side of the panel. The experimental data were compared with the strains and out-of-plane deflections from a high-fidelity nonlinear finite element analysis.

Mulani, Sameer B.↗
NASA NTRS1990

Damage assessment and residual compression strength of thick composite plates with through-the-thickness reinforcements

Damage in composite materials was studied with through-the-thickness reinforcements. As a first step it was necessary to develop new ultrasonic imaging technology to better assess internal damage of the composite. A useful ultrasonic imaging technique was successfully developed to assess the internal damage of composite panels. The ultrasonic technique accurately determines the size of the internal damage. It was found that the ultrasonic imaging technique was better able to assess the damage in a composite panel with through-the-thickness reinforcements than by destructively sectioning the specimen and visual inspection under a microscope. Five composite compression-after-impact panels were tested. The compression-after-impact strength of the panels with the through-the-thickness reinforcements was almost twice that of the comparable panel without through-the-thickness reinforcement.

Smith, Barry T.↗
NASA NTRS1991

Damage assessment and residual compression strength of thick composite plates with through-the-thickness reinforcements

Damage in composite materials was studied with through-the-thickness reinforcements. As a first step it was necessary to develop new ultrasonic imaging technology to better assess internal damage of the composite. A useful ultrasonic imaging technique was successfully developed to assess the internal damage of composite panels. The ultrasonic technique accurately determines the size of the internal damage. It was found that the ultrasonic imaging technique was better able to assess the damage in composite panel with through-the-thickness reinforcements than by destructively sectioning the specimen and visual inspection under a microscope. Five composite compression-after-impact panels were tested. The compression-after-impact strength of the panels with the through-the-thickness reinforcements was almost twice that of the comparable panel without through-the-thickness reinforcement.

Smith, Barry T.↗
NASA NTRS2015

Development and Testing of a Post-Installable Deepwater Monitoring System Using Fiber-Optic Sensors

This paper addresses the design and development of a fiber-optic monitoring system that can be deployed on existing deepwater risers and flowlines; and provides a summary of test article fabrication and the subsequent laboratory testing performed at the National Aeronautics and Space Administration-Johnson Space Center (NASA-JSC). A major challenge of a post-installed instrumentation system is to ensure adequate coupling between the instruments and the riser or flowline of interest. This work investigates the sensor coupling for pipelines that are suspended in a water column (from topside platform to seabed) using a fiber-optic sensor clamp and subsea bonding adhesive. The study involved the design, fabrication, and test of several prototype clamps that contained fiber-optic sensors. A mold was produced by NASA using 3-D printing methods that allowed the casting of polyurethane clamp test articles to accommodate 4-inch and 8-inch diameter pipes. The prototype clamps were installed with a subsea adhesive in a "wet" environment and then tested in the NASA Structures Test Laboratory (STL). The tension, compression, and bending test data showed that the prototype sensor clamps achieved good structural coupling, and could provide high quality strain measurement for active monitoring.

Seaman, Calvin H.↗
NASA NTRS2009

Overview of CEV Thermal Protection System Seal Development

NASA GRC supporting design, development, and implementation of numerous seal systems for the Orion CEV: a) HS-to-BS interface. b) Compression pad. HS-to-BS Interface Seal System: a) design has evolved as a result of changes with the CEV TPS. b) Seal system is currently under development/evaluation. Coupon level tests, Arc jet tests, and Validation test development. Compression Pad: a) Finalizing design options. b) Evaluating material candidates.

DeMange, Jeff↗
NASA NTRS2016

Evaluation of a Conductive Elastomer Seal for Spacecraft

An electrically conductive elastomer was evaluated as a material candidate for a spacecraft seal. The elastomer used electrically conductive constituents as a means to reduce the resistance between mating interfaces of a sealed joint to meet spacecraft electrical bonding requirements. The compound's outgassing levels were compared against published NASA requirements. The compound was formed into a hollow O-ring seal and its compression set was measured. The O-ring seal was placed into an interface and the electrical resistance and leak rate were quantified. The amount of force required to fully compress the test article in the sealing interface and the force needed to separate the joint were also measured. The outgassing and resistance measurements were below the maximum allowable levels. The room temperature compression set and leak rates were fairly high when compared against other typical spacecraft seal materials, but were not excessive. The compression and adhesion forces were desirably low. Overall, the performance of the elastomer compound was sufficient to be considered for future spacecraft seal applications.

elastomer↗
NASA NTRS2016

Evaluation of a Conductive Elastomer Seal for Spacecraft

An electrically conductive elastomer was evaluated as a material candidate for a spacecraft seal. The elastomer used electrically conductive constituents as a means to reduce the resistance between mating interfaces of a sealed joint to meet spacecraft electrical bonding requirements. The compound's outgassing levels were compared against published NASA requirements. The compound was formed into a hollow O-ring seal and its compression set was measured. The O-ring seal was placed into an interface and the electrical resistance and leak rate were quantified. The amount of force required to fully compress the test article in the sealing interface and the force needed to separate the joint were also measured. The outgassing and resistance measurements were below the maximum allowable levels. The room temperature compression set and leak rates were fairly high when compared against other typical spacecraft seal materials, but were not excessive. The compression and adhesion forces were desirably low. Overall, the performance of the elastomer compound was sufficient to be considered for future spacecraft seal applications.

Daniels, Christopher C.↗
NASA NTRS2004

Characterization of Composite Fan Case Resins

The majority of commercial turbine engines that power today s aircraft use a large fan driven by the engine core to generate thrust which dramatically increases the engine s efficiency. However, if one of these fan blades fails during flight, it becomes high energy shrapnel, potentially impacting the engine or puncturing the aircraft itself and thus risking the lives of passengers. To solve this problem, the fan case must be capable of containing a fan blade should it break off during flight. Currently, all commercial fan cases are made of either just a thick metal barrier or a thinner metal wall surrounded by Kevlar-an ultra strong fiber that elastically catches the blade. My summer 2004 project was to characterize the resins for a composite fan case that will be lighter and more efficient than the current metal. The composite fan case is created by braiding carbon fibers and injecting a polymer resin into the braid. The resin holds the fibers together, so at first using the strongest polymer appears to logically lead to the strongest fan case. Unfortunately, the stronger polymers are too viscous when melted. This makes the manufacturing process more difficult because the polymer does not flow as freely through the braid, and the final product is less dense. With all of this in mind, it is important to remember that the strength of the polymer is still imperative; the case must still contain blades with high impact energy. The research identified which polymer had the right balance of properties, including ease of fabrication, toughness, and ability to transfer the load to the carbon fibers. Resin deformation was studied to better understand the composite response during high speed impact. My role in this research was the testing of polymers using dynamic mechanical analysis and tensile, compression, and torsion testing. Dynamic mechanical analysis examines the response of materials under cyclic loading. Two techniques were used for dynamic mechanical analysis. The ARES Instrument analyzed the material through torsion. The second machine, TA Instruments apparatus, applied a bending force to the specimen. These experiments were used to explore the effects of temperature and strain rate on the stiffness and strength of the resins. The two different types of loading allowed us to verify our results. An axial-torsional load frame, manufactured by MTS Systems, Inc., was used to conduct the tensile, compression, and torsional testing. These tests were used to determine the stress-strain curves for the resins. The elastic and plastic deformation data was provided to another team member for characterization of high fidelity material property predictions. This information was useful in having a better understanding of the polymers so that the fan cases could be as sturdy as possible. Deformation studies are the foundation for the computational modeling that provides the structural design of a composite engine case as well as detailed analysis of the blade impact event.

Dvoracek, Charlene M.↗
NASA NTRS1974

Analysis of the three-point-bend test for materials with unequal tension and compression properties

Structural resins have moduli and strengths which are different in tension and compression. The three-point-bend test is used extensively in their characterization. An investigation is performed to derive all the equations needed for the analysis and test data reduction of the three-point-bend test. The governing equations are derived using well-known linear structural mechanics principles and are represented graphically. The stress concentration effects in the vicinity of the load point are investigated, and failure stress and failure initiation are examined.

Chamis, C. C.↗
NASA NTRS2014

An Overview of High Temperature Seal Development and Testing Capabilities at the NASA Glenn Research Center

The NASA Glenn Research Center (GRC), partnering with the University of Toledo, has a long history of developing and testing seal technologies for high-temperature applications. The GRC Seals Team has conducted research and development on high-temperature seal technologies for applications including advanced propulsion systems, thermal protection systems (airframe and control surface thermal seals), high-temperature preloading technologies, and other extreme-environment seal applications. The team has supported several high-profile projects over the past 30 years and has partnered with numerous organizations, including other government entities, academic institutions, and private organizations. Some of these projects have included the National Aerospace Space Plane (NASP), Space Shuttle Space Transport System (STS), the Multi-Purpose Crew Vehicle (MPCV), and the Dream Chaser Space Transportation System, as well as several high-speed vehicle programs for other government organizations. As part of the support for these programs, NASA GRC has developed unique seal-specific test facilities that permit evaluations and screening exercises in relevant environments. The team has also embarked on developing high-temperature preloaders to help maintain seal functionality in extreme environments. This paper highlights several propulsion-related projects that the NASA GRC Seals Team has supported over the past several years and will provide an overview of existing testing capabilities

National Aerospace Plane↗
NASA NTRSDate not supplied

Open-Hole Testing of Resin Infused Carbon Composite Laminates to Facilitate Damage Growth and Failure Analysis Tools for Structural Design

In manufacturing of carbon-fiber reinforced composite aircraft structures, resin infusion offers a highly repeatable process for manufacturing structural components with resin content control, low labor requirements, and complex curvatures. To further understand the structural capabilities of res-in infused composites (RIC), this study – as part of the NASA-led Hi-Rate Composite Aircraft Manufacturing project efforts – performed open hole tension (OHT) and open hole compression (OHC) testing on RIC laminates. This testing provides information on the damage morphology and growth characteristics of RICs, which fuels the development and evaluation of analysis tools for progressive damage growth and failure responses. X-ray computed tomography (XCT) was implemented on each OHC and OHT specimen prior to mechanical testing to identify preexisting damage and/or defects. Two OHT and OHC specimens were loaded monotonically to failure and an additional OHT and OHC specimen were loaded intermittently at defined conditions and XCT scanned after each run. From the data obtained in this study, damage mechanisms leading to failure were identified, damage morphology and size were assessed, and damage initiation and failure loads were measured.

HiCAM↗
NASA NTRS1989

Structural development of laminar flow control aircraft chordwise wing joint designs

For laminar flow to be achieved, any protuberances on the surface must be small enough to avoid transition to turbulent flow. However, the surface must have joints between the structural components to allow assembly or replacement of damaged parts, although large continuous surfaces can be utilized to minimize the number the number of joints. Aircraft structural joints usually have many countersunk bolts or rivets on the outer surface. To maintain no mismatch on outer surfaces, it is desirable to attach the components from the inner surface. It is also desirable for the panels to be interchangeable, without the need for shims at the joint, to avoid surface discontinuities that could cause turbulence. Fabricating components while pressing their outer surfaces against an accurate mold helps to ensure surface smoothness and continuity at joints. These items were considered in evaluating the advantages and disadvantages of the joint design concepts. After evaluating six design concepts, two of the leading candidates were fabricated and tested using many small test panels. One joint concept was also built and tested using large panels. The small and large test panel deflections for the leading candidate designs at load factors up to +1.5 g's were well within the step and waviness requirements for avoiding transition.The small panels were designed and tested for compression and tension at -65 F, at ambient conditions, and at 160 F. The small panel results for the three-rib and the sliding-joint concepts indicated that they were both acceptable. The three-rib concept, with tapered splice plates, was considered to be the most practical. A modified three-rib joint that combined the best attributes of previous candidates was designed, developed, and tested. This improved joint met all of the structural strength, surface smoothness, and waviness criteria for laminar flow control (LFC). The design eliminated all disadvantages of the initial three-rib concept except for unavoidable eccentricity, which was reduced and reacted satisfactorily by the rib supports. It should also result in a relatively simple low-cost installation, and makes it easy to replace any panels damaged in the field.

Fischler, J. E.↗
NASA NTRS2002

Compression Buckling Behavior of Large-Scale Friction Stir Welded and Riveted 2090-T83 Al-Li Alloy Skin-Stiffener Panels

To evaluate the potential of friction stir welding (FSW) as a replacement for traditional rivet fastening for launch vehicle dry bay construction, a large-scale friction stir welded 2090-T83 aluminum-lithium (Al-Li) alloy skin-stiffener panel was designed and fabricated by Lockheed-Martin Space Systems Company - Michoud Operations (LMSS) as part of NASA Space Act Agreement (SAA) 446. The friction stir welded panel and a conventional riveted panel were tested to failure in compression at the NASA Langley Research Center (LaRC). The present paper describes the compression test results, stress analysis, and associated failure behavior of these panels. The test results provide useful data to support future optimization of FSW processes and structural design configurations for launch vehicle dry bay structures.

Hoffman, Eric K.↗
NASA NTRS1996

A Comparison of Tension and Compression Creep in a Polymeric Composite and the Effects of Physical Aging on Creep Behavior

Experimental and analytical methods were used to investigate the similarities and differences of the effects of physical aging on creep compliance of IM7/K3B composite loaded in tension and compression. Two matrix dominated loading modes, shear and transverse, were investigated for two load cases, tension and compression. The tests, run over a range of sub-glass transition temperatures, provided material constants, material master curves and aging related parameters. Comparing results from the short-term data indicated that although trends in the data with respect to aging time and aging temperature are similar, differences exist due to load direction and mode. The analytical model used for predicting long-term behavior using short-term data as input worked equally as well for the tension or compression loaded cases. Comparison of the loading modes indicated that the predictive model provided more accurate long term predictions for the shear mode as compared to the transverse mode. Parametric studies showed the usefulness of the predictive model as a tool for investigating long-term performance and compliance acceleration due to temperature.

Gates, Thomas S.↗
NASA NTRS2014

Extending Our Understanding of Compliant Thermal Barrier Performance

Thermal barriers and seals are integral components in the thermal protection systems (TPS) of nearly all aerospace vehicles. They are used to minimize the flow of hot gases through interfaces and protect underlying temperature-sensitive components and systems. Although thermal barriers have been used extensively on many aerospace vehicles, the factors affecting their thermal and mechanical performance are not well-understood. Because of this, vehicle TPS designers are often left with little guidance on how to properly design and optimize these barriers. An ongoing effort to better understand thermal barrier performance and develop models and design tools is in progress at the NASA Glenn Research Center. Testing has been conducted to understand the degree to which insulation density influences structural performance and permeability. In addition, the development of both thermal and mechanical models is ongoing with the goal of providing an improved ability to design and implement these critical TPS components.

high temperature↗