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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Active Metal Brazing and Characterization of Brazed Joints in Titanium to Carbon-Carbon Composites

The Ti-metal/C-C composite joints were formed by reactive brazing with three commercial brazes, namely, Cu-ABA, TiCuNi, and TiCuSiI. The joint microstructures were examined using optical microscopy and scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS). The results of the microstructure analysis indicate solute redistribution across the joint and possible metallurgical bond formation via interdiffusion, which led to good wetting and spreading. A tube-on-plate tensile test was used to evaluate joint strength of Ti-tube/ C-C composite joints. The load-carrying ability was greatest for the Cu-ABA braze joint structures. This system appeared to have the best braze spreading which resulted in a larger braze/C-C composite bonded area compared to the other two braze materials. Also, joint loadcarrying ability was found to be higher for joint structures where the fiber tows in the outer ply of the C-C composite were aligned perpendicular to the tube axis when compared to the case where fiber tows were aligned parallel to the tube axis.

Singh, M.↗
NASA NTRS2011

In Situ Mechanical Property Measurements of Amorphous Carbon-Boron Nitride Nanotube Nanostructures

To understand the mechanical properties of amorphous carbon (a-C)/boron nitride nanotube (BNNT) nanostructures, in situ mechanical tests are conducted inside a transmission electron microscope equipped with an integrated atomic force microscope system. The nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation. We demonstrate multiple in situ tensile, compressive, and lap shear tests with a-C/BNNT hybrid nanostructures. The tensile strength of the a-C/BNNT hybrid nanostructure is 5.29 GPa with about 90 vol% of a-C. The tensile strength and strain of the end-to-end joint structure with a-C welding is 0.8 GPa and 5.2% whereas the lap shear strength of the side-by-side joint structure with a-C is 0.25 GPa.

Kim, Jae-Woo↗
NASA NTRS1983

Critical composite joint subcomponents: Analysis and test results

This program has been conducted to develop the technology for critical structural joints of a composite wing structure meeting design requirements for a 1990 commercial transport aircraft. A prime objective of the program was to demonstrate the ability to reliably predict the strength of large bolted composite joints. Load sharing between bolts in multirow joints was computed by a nonlinear analysis program (A4FJ) which was used both to assess the efficiency of different joint design concepts and to predict the strengths of large test articles representing a section from a wing root chord-wise splice. In most cases, the predictions were accurate to within a few percent of the test results. A highlight of these tests was the consistent ability to achieve gross-section failure strains on the order of 0.005 which represents a considerable improvement over the state of the art. The improvement was attained largely as the result of the better understanding of the load sharing in multirow joints provided by the analysis. The typical load intensity on the structural joints was about 40 to 45 thousand pound per inch in laminates having interspersed 37 1/2-percent 0-degree plies, 50-percent + or - 45-degrees plies and 12 1/2-percent 90-degrees plies. The composite material was Toray 300 fiber and Ciba-Geigy 914 resin, in the form of 0.010-inch thick unidirectional tape.

Bunin, B. L.↗
NASA NTRS1984

Design of an Advanced Wood Composite Rotor and Development of Wood Composite Blade Technology

In support of a program to advance wood composite wind turbine blade technology, a design was completed for a prototype, 90-foot diameter, two-bladed, one-piece rotor, with all wood/epoxy composite structure. The rotor was sized for compatibility with a generator having a maximum power rating of 4000 kilowatts. Innovative features of the rotor include: a teetering hub to minimize the effects of gust loads, untwisted blades to promote rotor power control through stall, joining of blades to the hub structure via an adhesive bonded structural joint, and a blade structural design which was simplified relative to earlier efforts. The prototype rotor was designed to allow flexibility for configuring the rotor upwind or downwind of the tower, for evaluating various types of teeter dampers and/or elastomeric stops, and with variable delta-three angle settings of the teeter shaft axis. The prototype rotor was also designed with provisions for installing pressure tap and angle of attack instrumentation in one blade. A production version rotor cost analysis was conducted. Included in the program were efforts directed at developing advanced load take-off stud designs for subsequent evaluation testing by NASA, development of aerodynamic tip brake concepts, exploratory testing of a wood/epoxy/graphite concept, and compression testing of wood/epoxy laminate, with scarf-jointed plies.

Stroebel, Thomas↗
NASA NTRS1980

Mechanical end joint for structural columns

Connector for tubular struts permits construction of lightweight frames without tools or assembly equipment. Two main components are node fitting and strut element. Components are aleaned approximately and pushed together. Design accommodates reasonable axial and rotational misalignment of nodes and struts. Also, individual columns can be inserted into receptacle and given slight push by operator, trigger pins release ratchet, allowing energy stored in springs to rotate screw into nut in receptacle.

Bush, H. G.↗
NASA NTRS1987

Joint Optics Structures Experiment (JOSE)

The objectives of the JOSE program is to develop, demonstrate, and evaluate active vibration suppression techniques for Directed Energy Weapons (DEW). DEW system performance is highly influenced by the line-of-sight (LOS) stability and in some cases by the wave front quality. The missions envisioned for DEW systems by the Strategic Defense Initiative require LOS stability and wave front quality to be significantly improved over any current demonstrated capability. The Active Control of Space Structures (ACOSS) program led to the development of a number of promising structural control techniques. DEW structures are vastly more complex than any structures controlled to date. They will be subject to disturbances with significantly higher magnitudes and wider bandwidths, while holding higher tolerances on allowable motions and deformations. Meeting the performance requirements of the JOSE program requires upgrading the ACOSS techniques to meet new more stringent requirements, the development of requisite sensors and acturators, improved control processors, highly accurate system identification methods, and the integration of hardware and methodologies into a successful demonstration.

Founds, David↗
NASA NTRS1942

Summary of Results of Tests Made by Aluminum Research Laboratories of Spot-welded Joints and Structural Elements

Available information concerning spot welding as a means of joining aluminum-alloy parts has been summarized and comparisons have been made of the relative merits of spot-welded and riveted aluminum-alloy structural elements. The results indicated that spot welding was as satisfactory as riveting insofar as resistance to static loads is concerned. Spot welds showed slightly lower resistance to impact loads but definitely lower resistance to repeated loads than rivets.

HARTMANN E C↗
NASA NTRS2015

Adhesively-Bonded Structural Composite Joint Utilizing Shoulder-Centered Sleeves

A composite joint includes a first member having a groove therein, a second member adjacent to the first member, and a connector member disposed between the second member and the first member. The connector member is received in the groove so as to bias a load path between the first member and the second member from a peripheral portion to a central portion of the connector member.

Lukowski, Florian P., Jr.↗
NASA NTRS1999

Microdynamic Behavior of a Joint Dominated Structure On-Orbit

The interferometry program experiments (IPEX) I and II are the first free-flying space experiments specifically designed to characterize the sub-micron microdynamic behavior of large flexible optical structures subjected to on-orbit thermal-mechanical disturbances.

flight↗
NASA NTRSDate not supplied

Structural Analysis, Modeling, and Testing of Multi-nut Joint for TriTruss Structure

The Multi-nut joint, developed at NASA Langley Research Center (LaRC), was designed to assemble TriTruss modules for a doubly curved 65.6-feet telescope support structure. Axial and bending tests for a multi-nut joint in the TriTruss structure were conducted to characterize the structural performance of the multi-nut joint and to obtain the installation torque value of the attachment fastener. This paper describes the summary of the axial and bending tests of the multi-nut joint, along with the test results. The equivalent axial stiffness (EA) and equivalent bending stiffness (EI) of the multi-nut joint were characterized based on these test results and are presented in this report. Additionally, finite element models (FEMs) of the axial and bending test specimens were developed, and the predicted axial and bending responses of the multi-nut joint were compared with the test results. Test-analysis comparison results show that the predicted axial load-displacement response of the test specimen was within 5 percent of the test results, while the predicted load-bending response of the test specimen exhibited a consistent trend with the test data.

TriTruss↗
NASA NTRS2024

Structural Analysis and Testing of Multi-nut Joint for TriTruss Structure

Axial and bending tests for a multi-nut joint in the TriTruss structure were conducted at NASA Langley Research Center (LaRC). This report describes the test procedures used for the axial and bending tests of the multi-nut joint, along with the test results. The joint's equivalent axial stiffness (EA) and equivalent bending stiffness (EI) were characterized based on these test results and are presented in this report. Additionally, finite element models (FEMs) of the axial and bending test specimens were developed, and the predicted axial and bending responses of the multi-nut joint were compared and validated with the test results.

Joint Test↗
NASA NTRSDate not supplied

Structural Analysis, Modeling, and Testing of Multi-nut Joint for TriTruss Structure

The Multi-nut joint, developed at NASA Langley Research Center (LaRC), was designed to assemble TriTruss modules for a doubly curved 65.6-feet telescope support structure. Axial and bending tests for a multi-nut joint in the TriTruss structure were conducted to characterize the structural performance of the multi-nut joint and to obtain the installation torque value of the attachment fastener. This paper describes the summary of the axial and bending tests of the multi-nut joint, along with the test results. The equivalent axial stiffness (EA) and equivalent bending stiffness (EI) of the multi-nut joint were characterized based on these test results and are presented in this report. Additionally, finite element models (FEMs) of the axial and bending test specimens were developed, and the predicted axial and bending responses of the multi-nut joint were compared with the test results. Test-analysis comparison results show that the predicted axial load-displacement response of the test specimen was within 5 percent of the test results, while the predicted load-bending response of the test specimen exhibited a consistent trend with the test data.

Structural analysis↗
NASA NTRS1986

Joint for Rapid Structural Assembly

Quickly attaching joint used in variety of truss structures. Split ring made in one piece and split radially after final machining. Mating tapers on split ring and endbells small: approximately 7 degrees. Tapers of this range permit high internal preloads to be obtained, yet parts easily separated when collar released. Results from tests on developmental model indicate load-displacement response linear and substantial preloading accomplished. Quickly-erecting truss structures have variety of applications, from Earth to space-station keel beams, antenna masts, and large platforms.

Rhodes, M. D.↗
NASA NTRS1988

Effects of joints in truss structures

The response of truss-type structures for future space applications, such as Large Deployable Reflector (LDR), will be directly affected by joint performance. Some of the objectives of research at BAC were to characterize structural joints, establish analytical approaches that incorporate joint characteristics, and experimentally establish the validity of the analytical approaches. The test approach to characterize joints for both erectable and deployable-type structures was based upon a Force State Mapping Technique. The approach pictorially shows how the nonlinear joint results can be used for equivalent linear analysis. Testing of the Space Station joints developed at LaRC (a hinged joint at 2 Hz and a clevis joint at 2 Hz) successfully revealed the nonlinear characteristics of the joints. The Space Station joints were effectively linear when loaded to plus or minus 500 pounds with a corresponding displacement of about plus or minus 0.0015 inch. It was indicated that good linear joints exist which are compatible with errected structures, but that difficulty may be encountered if nonlinear-type joints are incorporated in the structure.

Ikegami, R.↗
NASA NTRS1991

Dynamic Analyses Including Joints Of Truss Structures

Method for mathematically modeling joints to assess influences of joints on dynamic response of truss structures developed in study. Only structures with low-frequency oscillations considered; only Coulomb friction and viscous damping included in analysis. Focus of effort to obtain finite-element mathematical models of joints exhibiting load-vs.-deflection behavior similar to measured load-vs.-deflection behavior of real joints. Experiments performed to determine stiffness and damping nonlinearities typical of joint hardware. Algorithm for computing coefficients of analytical joint models based on test data developed to enable study of linear and nonlinear effects of joints on global structural response. Besides intended application to large space structures, applications in nonaerospace community include ground-based antennas and earthquake-resistant steel-framed buildings.

Belvin, W. Keith↗
NASA NTRS2018

Improved Pyrotechnic Shock Scaling Method Based on Shock Response Spectrum and Statistical Energy Analysis

It has been more than forty years since the pyrotechnic shock scaling method was introduced. The scaling method estimates the attenuation of the Shock Response Spectrum (SRS) based on the distance from the source, structural configurations, types of structural joints and interfaces, and intervening structure [1]. The method has been successfully used in the spacecraft community countless times and still is frequently used to develop pyrotechnic shock requirements at various levels of assembly of a spacecraft. However, since the method was derived empirically from a limited set of shock test data [2], the aerospace community has been looking for an alternative approach. In this paper, a computational scaling method based on Statistical Energy Analysis (SEA) is re-visited. SEA is traditionally used as a method for investigating the diffusion of acoustic and vibratory energies of a system at steady-state [3]. Previously, an approach using the SRS as an acceleration constraint condition to the SEA model was introduced to estimate the attenuation from a shock source [4,5]. In the current investigation, additional examples are provided to further validate the approach. In addition, responses in the time domain are produced by the Local Modal Phase Reconstruction (LMPR) approach which was recently introduced to the community [6].

Fernandez, Juan P.↗
NASA NTRS1990

High temperature turbine engine structure

A high temperature turbine engine includes a hybrid ceramic/metallic rotor member having ceramic/metal joint structure. The disclosed joint is able to endure higher temperatures than previously possible, and aids in controlling heat transfer in the rotor member.

Boyd, Gary L.↗