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Results for “ADHESION”

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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Application of strain gages to measure adhesive strains through the thickness of an adhesively-bonded stiffened strip

The purpose of the study is to measure the through-the-thickness strain distribution in an adhesively bonded stiffened strip subject to four-point bending and to compare the distribution with predicted results. Small-strain gages are used for measuring the normal strain in the adhesive layer of the strip. A total of 16 120-ohm encapsulated strain gages were mounted on the adhesive layer, and the specimen was loaded quasi-statistically and never to failure. Both the experimental and analytical results show good correlation and, in particular, a high strain gradient acting near the edge of the adhesive layer.

Lopez, O. F.↗
DOE OSTI2021

Laser-Interference Surface Preparation for Enhanced Coating Adhesion and Adhesive Joining of Multi-Materials (Final Project Report)

This report investigates a laser-interference surface treatment as a non-contact, i.e., without major solid/liquid medium application or abrasion, and non-chemical surface preparation method for aerospace coating systems. It was proposed to use the laser-interference technique to structure surfaces of Al and/or Ti, creating "rough" surfaces with pre-engineered series of ridges and valleys at submicron scale. The science goal of this study was to develop an understanding of the surface microstructure, topology, and physical mechanisms that would improve adhesion and corrosion protection of Al2024-T3. Microstructure analysis indicates that the laser-interference structuring (LIS) was found to reduce the formation of CuMn-rich precipitates in Al 2024-T3 over a 500-800 nm depth from top surface. The X-cut and cross-hatch coating adhesion ratings indicate that the LIS specimens meet the performance requirements in the coating adhesion specifications by having a higher or identical ranking to those specimens prepared with current state-of-the-art chemical conversion or sulfuric acid anodizing. After the ASTM B117 corrosion exposure, it was found that the laser processed specimens exhibited only few blisters. It was found that the corrosion damage was minimized at a laser rastering speed of 4 mm/s, for which only 33% of specimens developed very minor corrosion damage. The ASTM D1654 creepage ratings, used to evaluate corrosion damage along the scribe lines, were found to be at least nine for all coated panels. These results indicate that the laser-interference technique with the additional acetone wiping has the potential to be further developed as a minor chemical surface preparation technique for chromate-containing epoxy primers coatings.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Enhanced copper–carbon nanotube hybrid conductors with titanium adhesion layer

Cu–carbon nanotube (CNT) hybrids combine the advantages of the high electrical conductivity of Cu with the low temperature coefficient of resistance for CNTs, but require enhanced interfacing to improve the electrical performance when exposed to elevated temperatures. In this work, Ti and Ni were investigated as adhesion metals by thermally evaporating 10 nm layers onto a CNT conductor. SEM analysis shows Ni deposits as discrete nanoscale crystallites which coalesce after annealing to 400 °C in H 2 /Ar. Ti deposits uniformly along the CNT surface and is stable over such temperatures. A 100 nm deposition of Cu is shown to delaminate from the CNTs after annealing, and the resistance per length (R/L) increases by 40%. The Cu–Ni–CNT exhibits a 125% increase, while the Cu–Ti–CNT achieves a 12% decrease in R/L, for similar annealing conditions. Thus, Ti emerges as an effective adhesion metal, warranting its use in metal–CNT wire technologies for elevated temperature operation.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Intercellular Adhesion Molecule-1 and Vascular Cell Adhesion Molecule Are Induced by Ionizing Radiation on Lymphatic Endothelium

Purpose/Objectives: The goal of this study was to assess the effects of ionizing radiation on the expression of the integrin ligands ICAM-1 and VCAM that control leucocyte transit by lymphatic endothelial cells. Materials/Methods: Confluent monolayers of primary human lymphatic endothelial cells (LEC) were irradiated with single dose of 2, 5, 10 or 20 Gy, with 6 MeV-x-rays using a Linear-Accelerator. ICAM-1 and VCAM expression was determined by flow cytometry. Human tissue specimens received a single dose of 20 Gy with 15 MeV-x-rays. MC38, B16-OVA or B16-VEGF-C tumors grown in C57BL/6 mice were irradiated with single dose of 20Gy using a Linear-Accelerator fitted with a 10mm Radiosurgery collimator. Clinical samples were obtained from patients previous and 4 weeks after complete standard radiotherapy. ICAM-1 and VCAM expression was detected in all tissue specimens by confocal microscopy. To understand the role of TGFβ in this process anti-TGFβ blocking mAb were injected i.p. 30min before radiotherapy. Cell adhesion to irradiated LEC was analyzed in adhesion experiments performed in the presence or in the absence of anti- TGFβ and /or anti-ICAM1 blocking mAb. Results: We demonstrate that lymphatic endothelial cells in tumor samples experience induction of surface ICAM-1 and VCAM when exposed to ionizing radiation in a dose- and time-dependent manner. These effects can be recapitulated in cultured LEC, and are in part mediated by TGFβ. These data are consistent with increases in ICAM-1 and VCAM expression on LYVE-1+ endothelial cells in freshly explanted human tumor tissue and in mouse transplanted tumors after radiotherapy. Finally, ICAM-1 and VCAM expression accounts for enhanced adherence of human T lymphocytes to irradiated LEC. Conclusion: Our results show induction of ICAM-1 and VCAM on LVs in irradiated lesions and offer a starting point for elucidating the biological and therapeutic implications of targeting leukocyte traffic in combination to immunotherapy.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
NASA NTRSDate not supplied

In-Situ Ice Adhesion Testing using the Deformed Skin Adhesion Test

There exists a plethora of ice adhesion testing methods such as centrifuge-based methods, push/pull methods, and lap joint shear tests. However, these methods often cannot be done in-situ during an icing spray and require researcher handling/preparation prior to testing. Additionally, many of these methods test ice accretions that are not representative of the ice shapes that grow on airframes which can have unintended consequences such as edge or corner stress concentrations. In order to mitigate the issues present with other ice adhesion tests a novel, hands-free, in-situ test method imbedded into the leading edge of the airfoil has been developed and tested in the NASA Glenn Research Center Icing Research Tunnel. The mechanics of the new test method are discussed with finite element simulations being used to highlight the fundamental mechanics of this test method. The testing procedures used during the experimental test campaign are discussed along with the icing cloud test matrix. Analysis of the force-displacement results highlights the repeatability of the test method with regards to both sample behavior across several days of testing and different ice shapes. The results from first run of the day showed a significant discrepancy from subsequent runs and differential image analysis was used to determine differences in the interfacial bonding states between runs.

Ice Adhesion↗
NASA NTRSDate not supplied

In-Situ Ice Adhesion Testing using the Deformed Skin Adhesion Test

There exists a plethora of ice adhesion testing methods such as centrifuge-based methods, push/pull methods, and lap joint shear tests. However, these methods often cannot be done in-situ during an icing spray and require researcher handling/preparation prior to testing. Additionally, many of these methods test ice accretions that are not representative of the ice shapes that grow on airframes which can have unintended consequences such as edge or corner stress concentrations. In order to mitigate the issues present with other ice adhesion tests a novel, hands-free, in-situ test method imbedded into the leading edge of the airfoil has been developed and tested in the NASA Glenn Research Center Icing Research Tunnel. The mechanics of the new test method are discussed with finite element simulations being used to highlight the fundamental mechanics of this test method. The testing procedures used during the experimental test campaign are discussed along with the icing cloud test matrix. Analysis of the force-displacement results highlights the repeatability of the test method with regards to both sample behavior across several days of testing and different ice shapes. The results from first run of the day showed a significant discrepancy from subsequent runs and differential image analysis was used to determine differences in the interfacial bonding states between runs.

Ice Adhesion↗
DOE OSTI2020

Polymer-cement composites with adhesion and re-adhesion (healing) to casing capability for geothermal wellbore applications

Deterioration of cement/casing adhesion in wellbore scenarios can result in unwanted and potentially harmful leakage with the potential of serious repair costs. In this work, we explore the use of self-healing polymers added to conventional wellbore cements as a way to bring about self-healing and readhering (to steel casing) properties to the composite material. The polymers are pH resistant and seem to improve the cement integrity after exposure to typical chemical and thermal stresses encountered under geothermal wellbore conditions. We find that addition of about 10-15 wt% of polymer to the cement visually increases its resistance to fracturing from exposure to geothermal conditions, while the adhesive strength of cement/stainless steel increases with curing time for a period of about 10 days. Self-healing capability was demonstrated by permeability analysis showing that polymer-cement composites reduce flow by 50-70% at cement bulk and at the cement/steel interface. Use of atomistic simulations imply that these polymers have good wetting properties on the steel surfaces. Analysis of the interactions between steel/polymer and cement/polymer show that they are complementary, resulting in a wider range of bonding patterns. Cracks are likely to expose under-coordinated sites that result in more bonding interactions, which agrees well with the permeability measurements showing high degree of healed cracks and healed (cement-steel) interfacial gaps together with an overall increased in structural integrity of these advanced polymer-cement composite materials.

Rod, Kenton A.↗
NASA NTRS2016

Modified Surface Having Low Adhesion Properties to Mitigate Insect Residue Adhesion

A process to modify a surface to provide reduced adhesion surface properties to mitigate insect residue adhesion. The surface may include the surface of an article including an aircraft, an automobile, a marine vessel, all-terrain vehicle, wind turbine, helmet, etc. The process includes topographically and chemically modifying the surface by applying a coating comprising a particulate matter, or by applying a coating and also topographically modifying the surface by various methods, including but not limited to, lithographic patterning, laser ablation and chemical etching, physical vapor phase deposition, chemical vapor phase deposition, crystal growth, electrochemical deposition, spin casting, and film casting.

Wohl, Christopher J., Jr.↗
DOE OSTI2022

Potential-Dependent Adhesion Forces between dsDNA and Electroactive Surfaces

A promising approach to regulating the interactions between polyelectrolytes and materials is the use of electroactive surfaces that can change their charge state. However, common electroactive groups are too unstable to be practical for this purpose. Here we have performed a single molecule force spectroscopy study of the interactions between dsDNA and an 1,1'-biferrocenylene (BFD = bis(fulvalene)diiron)-terminated self-assembled monolayer surface that allows us to reversibly change the charge state. We found that the interaction force between DNA and the surface is correlated to the oxidation state of the BFD groups, which is conveniently controlled by the electrochemical potentials. We discovered that the electroactive SAM produces much stronger interaction forces than its nonelectroactive counterpart. A model based on the Grahame equation was able to quantitatively reproduce the experimentally observed relation between the applied potentials and adhesion forces. Our electroactive surface provides a model system for quantitative studies of the interactions between polyelectrolyte and charged surfaces in liquid. Furthermore, these insights may enable new opportunities for actively manipulating the binding, orientations, and conformations of polyelectrolytes for biosensing, nanomotors, and other applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗