Search NASA⌕ Search

SEARCH · Search NASA

Results for “Mechanical testing”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Grain boundary slip – twin transmission in titanium

Here, using a combination of mechanical testing, scanning electron microscopy, and a unified crystal plasticity framework for discrete intragranular shear localization, we investigate intense, localized slip bands on prismatic planes and {10$\bar{1}$2} $\langle$$\bar{1}$011$\rangle$ tensile twins, and their transmission across the grain boundaries (GBs) in commercially pure titanium. The analyses show that the orientation and curvature of the GB influence the local stress fields at the GBs, and consequently, the slip/twin transmission across the boundary. In addition to host grain properties, neighboring grain properties, such as active slip systems and instances of heterogeneity like slip bands and twins, heavily affect the deformation mechanisms in each grain. Finally, the applicability of geometric factors to predict the transmission in the experimentally observed co-located pairs is discussed. The local stress field calculated by the discrete slip and twin band model is shown to be capable of determining whether a transmission has occurred in an observed co-located pair, and also the direction of the transmission.

36 MATERIALS SCIENCE↗
NASA NTRS2001

Packaging Technology Developed for High-Temperature Silicon Carbide Microsystems

High-temperature electronics and sensors are necessary for harsh-environment space and aeronautical applications, such as sensors and electronics for space missions to the inner solar system, sensors for in situ combustion and emission monitoring, and electronics for combustion control for aeronautical and automotive engines. However, these devices cannot be used until they can be packaged in appropriate forms for specific applications. Suitable packaging technology for operation temperatures up to 500 C and beyond is not commercially available. Thus, the development of a systematic high-temperature packaging technology for SiC-based microsystems is essential for both in situ testing and commercializing high-temperature SiC sensors and electronics. In response to these needs, researchers at Glenn innovatively designed, fabricated, and assembled a new prototype electronic package for high-temperature electronic microsystems using ceramic substrates (aluminum nitride and aluminum oxide) and gold (Au) thick-film metallization. Packaging components include a ceramic packaging frame, thick-film metallization-based interconnection system, and a low electrical resistance SiC die-attachment scheme. Both the materials and fabrication process of the basic packaging components have been tested with an in-house-fabricated SiC semiconductor test chip in an oxidizing environment at temperatures from room temperature to 500 C for more than 1000 hr. These test results set lifetime records for both high-temperature electronic packaging and high-temperature electronic device testing. As required, the thick-film-based interconnection system demonstrated low (2.5 times of the room-temperature resistance of the Au conductor) and stable (decreased 3 percent in 1500 hr of continuous testing) electrical resistance at 500 C in an oxidizing environment. Also as required, the electrical isolation impedance between printed wires that were not electrically joined by a wire bond remained high (greater than 0.4 GW) at 500 C in air. The attached SiC diode demonstrated low (less than 3.8 W/mm2) and relatively consistent dynamic resistance from room temperature to 500 C. These results indicate that the prototype package and the compatible die-attach scheme meet the initial design standards for high-temperature, low-power, and long-term operation. This technology will be further developed and evaluated, especially with more mechanical tests of each packaging element for operation at higher temperatures and longer lifetimes.

Chen, Liang-Yu↗
DOE OSTI2025

Mineralized sclerites in the gorgonian coral Leptogorgia chilensis as a natural jamming system

The soft corals (Cnidaria, Octocorallia), a diverse group of colonial marine invertebrates, can reversibly tune their body stiffness in response to external stimuli. This capability is attributed to their dynamic skeletal systems, which consist of thousands of mineralized skeletal elements, called sclerites, embedded within a gel-like matrix that swells/deswells and unjams/jams the sclerites, thus modulating skeletal stiffness. While sclerite morphology is widely used for species identification, its role in the mechanical performance of a soft coral’s skeletal system is largely unknown. Here, we investigated structure-jamming relationships in sclerite-based skeletal architectures using the red gorgonian octocoral Leptogorgia chilensis as a model system. The sclerites of L. chilensis exhibit a shaft-like geometry with two axial branches and two sets of triradiate side branches, which are aligned with the crystallographic symmetry of the constituent magnesium-containing calcite. By combining multiscale three-dimensional (3D) structural characterization, parametric geometrical modeling, 3D printing, mechanical testing, and discrete element simulations, we demonstrate how sclerite geometry achieves a balanced jamming performance in terms of stiffness, weight, strength, and fracture resistance in comparison to alternative geometries parametrically modified from the native sclerites (e.g., changes in the length and number of side branches). Here, we also found that these performance metrics are achieved through the effective interlocking among side and axial branches, which is further enhanced by the fractal-like microscopic spikes on the branch tips. The findings in this natural jamming system offer insights for designing synthetic mechanotunable material architectures for a wide range of applications, from soft robotics to mechanical dampeners.

36 MATERIALS SCIENCE↗
NASA NTRS1999

Monolithic Cu-Cr-Nb Alloys for High Temperature, High Heat Flux Applications

Work during the prior four years of this grant has resulted in significant advances in the development of Cu-8 Cr4 Nb and related Cu-Cr-Nb alloys. The alloys are nearing commercial use in the Reusable Launch Vehicle (RLV) where they are candidate materials for the thrust cell liners of the aerospike engines being developed by Rocketdyne. During the fifth and final year of the grant, it is proposed to complete development of the design level database of mechanical and thermophysical properties and transfer it to NASA Glenn Research Center and Rocketdyne. The database development work will be divided into three main areas: Thermophysical Database Augmentation, Mechanical Testing and Metallography and Fractography. In addition to the database development, work will continue that is focussed on the production of alternatives to the powder metallurgy alloys currently used. Exploration of alternative alloys will be aimed at both the development of lower cost materials and higher performance materials. A key element of this effort will be the use of Thermo-Calc software to survey the solubility behavior of a wide range of alloying elements in a copper matrix. The ultimate goals would be to define suitable alloy compositions and processing routes to produce thin sheets of the material at either a lower cost, or, with improved mechanical and thermal properties compared to the current Cu-Cr-Nb powder metallurgy alloys.

Ellis, David L.↗
DOE OSTI2026

Establishment of a Vertically Integrated Domestic Manufacturing Process for Production of Substrates Needed for Manufacture of Gas Diffusion Layers

In this project, AvCarb, LLC evaluated the baseline performance metrics of commercial carbon veils and their corresponding Gas Diffusion Layers (GDLs) with the goal of establishing an optimized, vertically integrated production system for wet-laid nonwoven substrates used in gas diffusion media for electrochemical energy storage and conversion devices. Mechanical testing and microstructural characterization were conducted and used to develop a multiscale computational model capable of simulating and predicting the performance of GDLs in fuel cells. Although the project successfully generated foundational transport and modeling data, it was terminated prior to identifying the critical GDL design parameters necessary for full optimization. The program aimed to improve carbon veil fabrication through enhanced fiber dispersion, fiber-fiber adhesion control, and improved web formation, enabling the production of high-quality, uniform substrates. Simulations were intended to guide mixing and solution delivery system design and process conditions, followed by production-scale trials to evaluate fiber dispersion, web uniformity, and mechanical robustness. At full deployment, the proposed production line would have been capable of producing approximately 650,000 m² of carbon veil annually. This capability remains strategically important, as the United States currently lacks a domestic source of wet-laid nonwoven carbon substrates that satisfy the stringent quality requirements for fuel-cell GDLs and electrolyzers representing an ongoing supply-chain vulnerability. Beyond supply-chain benefits, the project established a robust benchmarking dataset for existing commercial carbon veils while advancing next-generation material concepts targeting improved performance and manufacturing consistency.

Olson, Cynthia Lemay↗
NASA NTRS2004

Fabrication and Testing of Habitat Components Using In-Situ Materials for Martian Exploration

The development of Mars for human activity will require the utilization of Martian materials in building habitats and working structures. One approach is to use polymer binders with regolith to form structural elements. Not only can useful composite materials be produced in this way but the radiation protection properties are also increased. This is important since only modest protection from space radiation is provided by the Martian atmosphere. We have studied composites fabricated using Martian regolith simulant and polymers which can be synthesized from local Martian materials for their potential use as radiation shields for manned Mars missions. To validate shielding effectiveness, composites are irradiated with a 55 MeV proton beam and neutron beams up to 800 MeV. Shielding effects on microelectronic devices are measured by placing them behind samples of the composites during irradiation. To measure structural properties of the composites, preliminary characterization and mechanical testing are made for the composites.

Kim, M.-H. Y.↗
NASA NTRS1987

Impulsive H-alpha diagnostics of electron-beam-heated solar flare model chromospheres

Time-dependent H-alpha profiles were computed for the dynamic model atmospheres of Fisher, Canfield, and McClymont (1985) simulating the effects of an intense impulsively initiated power-law beam of electrons incident on the chromosphere. The temporal response of H-alpha arises from three separate physical mechanisms, whose relative importance varies over the line profile. The fastest variations (typically less than 0.1 s for the explosive heating discussed here) arise from energy imbalance; these are apparent on chromospheric heating and cooling time scales and have their greatest amplitude at line center. Slower variations arise from ionization imbalance and are most apparent in the blue wing. The slowest variations arise from hydrodynamic effects and are related to the formation of a chromospheric condensation; these are most apparent in the red wing. These results provide a basis for the design and analysis of observations of H-alpha, in coordination with hard X-rays or microwaves, to test mechanisms of energy transport in solar flares.

Canfield, Richard C.↗
DOE OSTI2021

Property enhancement of CoCrNi medium-entropy alloy by introducing nano-scale features

CoCrNi -medium-entropy alloy (MEA) has been widely investigated due to its superior mechanical properties that overcome strength-ductility tradeoff. Here we show further property enhancement of CoCrNi MEA by introducing nano-scale features. Both CoCrNi and oxide dispersion strengthened (ODS) CoCrNi are fabricated by mechanical alloying and spark plasma sintering. Microstructural characterization and mechanical testing of these nanostructured MEAs revealed that the nano-scale features significantly improves the strength of the alloys. In ODS-CoCrNi MEA, Y 2 Ti 2 O 7 oxides with an average diameter of 7.3 ± 3.2 nm are incoherent with the matrix, and a specific orientation relationship exists between Y 2 Ti 2 O 7 and the matrix, which is [011] Y 2 Ti 2 O 7 //[011]Matrix, (400) Y 2 Ti 2 O 7 //(200)Matrix and ($22\bar2$) Y 2 Ti 2 O 7 //($11\bar1$)Matrix. The recrystallization and grain growth processes are effectively suppressed by the introduction of Y 2 Ti 2 O 7 nanoparticles. Strengthening mechanism analyses indicate that the strength improvement of ODS-CoCrNi is mainly ascribed to the precipitation strengthening of Y 2 Ti 2 O 7 .

36 MATERIALS SCIENCE↗
NASA NTRS2022

Building and Breaking Carbon Composites with REACTER

Carbon-based composites have become indispensable materials in aerospace and other high-performance applications, yet obtaining a detailed, nanoscale understanding of their morphology and failure mechanisms using only experimental methods remains a difficult challenge. REACTER is a versatile computational modeling tool for atomistic molecular dynamics simulations designed to model chemical reactions at the speed and length scales of classical force fields. In this work, several recent features of REACTER were applied to the creation and subsequent mechanical testing of two classes of carbon composites: carbon nanotube (CNT) composites and carbon fiber reinforced polymers (CFRP). A network of CNTs was grown dynamically using the new ‘create atoms’ feature of REACTER. The CNT filler was embedded into a polyarylacetylene (PAA) matrix by simulated in situ polymerization to obtain the final composite model. To generate the second class of carbon composite, fully carbonized (graphitic) carbon fiber morphologies were created by the method of Desai et al. [1], but using the advanced reaction constraints framework of REACTER. Two fiber models were created, representing a circular carbon fiber core and a flat surface, and similarly infiltrated with resin to obtain the final CFRP structure. Failure mechanisms were elucidated by simulating mechanically induced bond breaking, as characterized by third order DFT-based tight-binding simulations, via a reaction constraint on the total potential energy of the involved atoms.

Polymer↗
DOE OSTI2020

Sapphire advanced mitigation process: wet etch to expose sub-surface damage and increase laser damage resistance and mechanical strength

In this study, a novel, to the best of our knowledge, method of wet chemical etching of sapphire workpieces (such as optics, wafers, windows, and cones), called the sapphire advanced mitigation process (or sapphire AMP), has been developed that exposes sub-surface mechanical damage created during the optical fabrication process and significantly enhances the surface laser damage resistance (> 2×) and mechanical strength (up to ~ 2.6×). Sapphire AMP involves first treating the workpiece with a mixture of sulfuric and phosphoric acid ([H 2 SO 4 ]:[H 3 PO 4 ]= 1 : 3) at 220°C, followed with phosphoric acid at 160°C, then with sodium hydroxide base (NaOH) and surfactant at 40°C, and finally with a high-pressure deionized water spray rinse. Sapphire AMP has been demonstrated on both A- and C-plane sapphire workpieces. The mechanism of this etch process involves the reaction of the sapphire (Al 2 O 3 ) surface with sulfuric acid (H 2 SO 4 ) forming aluminum sulfate [Al2(SO4)3], which has low solubility. The high phosphoric acid content in the first and second steps of sapphire AMP results in the efficient conversion of Al 2 (SO 4 ) 3 to aluminum phosphate (AlPO 4 ), which is very soluble, greatly reducing reaction product redeposition on the workpiece surface. Sapphire AMP is shown to expose sub-surface mechanical damage on the sapphire surface created during the grinding and polishing processes, whose etched morphology has either isotropic or anisotropic evolution depending on the nature of the initial surface damage. Sapphire AMP was also designed to remove the key known surface, laser absorbing precursors (namely, foreign chemical impurities, the fracture surface layer of preexisting sub-surface damage, and reaction product or foreign species redeposition or precipitation). Static and sliding indention induced surface microfractures on sapphire are shown after sapphire AMP to have a significant decrease in the fast photoluminescence intensity (a known metric for measuring the degree of laser damaging absorbing precursors). In addition, the onset of laser damage (at 351 nm 3 ns) on sapphire AMP treated workpieces was shown to increase in fluence from ~ 4 to >9.5J/cm 2 . Finally, biaxial ball-on-ring mechanical tests on sapphire disks showed an increase in the failure stress from 340 MPa (with pre-existing 28 µm flaws) to ~ 900MPa after sapphire AMP, which is attributed to the blunting of the surface microfractures.

36 MATERIALS SCIENCE↗
NASA NTRS2010

Laser Surface Preparation and Bonding of Aerospace Structural Composites

Adhesive bonds are critical to the integrity of built-up structures. Disbonds can often be detected but the strength of adhesion between surfaces in contact is not obtainable without destructive testing. Typically the number one problem in a bonded structure is surface contamination, and by extension, surface preparation. Standard surface preparation techniques, including grit blasting, manual abrasion, and peel ply, are not ideal because of variations in their application. Etching of carbon fiber reinforced plastic (CFRP) panels using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser appears to be a highly precise and promising way to both clean a composite surface prior to bonding and provide a bond-promoting patterned surface akin to peel ply without the inherent drawbacks from the same (i.e., debris and curvature). CFRP surfaces prepared using laser patterns conducive to adhesive bonding were compared to typical prebonding surface treatments through optical microscopy, contact angle goniometry, and post-bonding mechanical testing.

Belcher, M. A.↗
NASA NTRS2010

Laser Surface Preparation for Adhesive Bonding of Aerospace Structural Composites

Adhesive bonds are critical to the integrity of built-up structures. Disbonds can often be detected but the strength of adhesion between surfaces in contact is not obtainable without destructive testing. Typically the number one problem in a bonded structure is surface contamination, and by extension, surface preparation. Standard surface preparation techniques, including grit blasting, manual abrasion, and peel ply, are not ideal because of variations in their application. Etching of carbon fiber reinforced plastic (CFRP) panels using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser appears to be a highly precise and promising way to both clean a composite surface prior to bonding and provide a bond-promoting patterned surface akin to peel ply without the inherent drawbacks from the same (i.e., debris and curvature). CFRP surfaces prepared using laser patterns conducive to adhesive bonding were compared to typical pre-bonding surface treatments through optical microscopy, contact angle goniometry, and post-bonding mechanical testing.

Belcher, M. A.↗
NASA NTRSDate not supplied

Building and Breaking Carbon Composites with REACTER

Carbon composites have become indispensable for aerospace and other high-performance applications, and a detailed picture of their morphology and failure mechanisms remains difficult to obtain through experiment. REACTER is a versatile computational modeling tool for atomistic molecular dynamics designed to model chemical reactions at the speed and length scales of classical force fields.1 In this work, several recent features of REACTER were applied to the creation and subsequent mechanical testing of two classes of carbon composites, carbon-fiber reinforced polymers (CFRP) and carbon nanotube (CNT) composites. Carbon fiber core morphologies were created by the method of Desai et al.,2 but using the advanced reaction constraints framework of REACTER, their proposed multistep procedure was reduced to a single uninterrupted molecular dynamics simulation. The carbon fiber filler was embedded into a polymer matrix by simulated in situ polymerization of several thermosetting resins, including bismaleimide and polyarylacetylene, to obtain the final CFRP model. To generate the second class of carbon composite, CNT networks were grown dynamically using the new ‘create atoms’ feature of REACTER, and similarly infiltrated with resin to obtain CNT composites. The resulting models were compared directly to experiment using simulated high resolution transmission electron microscopy and x-ray diffraction. Failure mechanisms were elucidated by simulating mechanically induced bond breaking, as characterized by third-order DFT-based tight-binding (DFTB3) simulations, via a reaction constraint on the total potential energy of the involved atoms.

Molecular Dynamics↗
DOE OSTI2026

Tailored Silicone Network Architecture for Ultimate Mechanical Reinforcement

Hydrosilylation cured silicone elastomers are subject to reaction inefficiency, leading to incomplete and non-uniform crosslink networks, restricting the potential of mechanical reinforcement. This work investigates pre-synthesized, functional PDMS architectures as additives to improve ultimate mechanical performance relative to conventional single-step curing. Three custom, functional structures were prepared: a partially crosslinked PDMS scaffold (Structure A), a bottle-brush PDMS (Structure B), and a star-shaped PDMS derived from an MQ resin (Structure C). Rheological characterization was used to identify the ultimate design space and proper stoichiometric ratio for Structure A, and confirm successful formation of all structures for suitable incorporation into a base silicone formulation at 30wt%. Mechanical tests indicated that all three structures increased in ultimate tensile strength relative to their single-step counterparts, with Structure A providing additional improvements to toughness (432 vs. 258 kJ/m3) and ultimate elongation (158 vs. 115%). Furthermore, Structure B remained very soft in the unfilled state, while Structure C provided hardness (23 vs. 18 Shore A) and stiffness (780 vs. 420 kPa Young’s modulus) increases. In silica filled systems, Structure A retained increased strength but reduced elongation, while Structure B indicated strong reinforcement in terms of strength, toughness, and stiffness. Thermal analysis on the cure profiles of these materials suggested that pre-formation of network architectures enable a more complete reaction than a single-step process (15.9 vs. 15.1 J/g). Ultimately, these results indicate that tailoring PDMS architecture before the final cure can improve ultimate mechanical properties via improved network development in silicone elastomers. Furthermore, this work offers a promising strategy for designing higher-performance, more tunable silicone formulations.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Project 7.3 Characterization of Kevlar®-reinforced Composites for Predictive Simulation

The IACMI 7.3 project between DuPont and Purdue University required the mechanical testing of a 2x2 twill Kevlar® weave with Hexion EPIKOTE resin. The tension, shear, flexure, and compressive behavior of this material system was characterized, and the results can be seen in Table 1. These material properties can now be further evaluated for use in performance simulations of automotive components to represent the properties of composites based on woven materials containing Kevlar. This report will provide details regarding the effort required to arrive at these material properties.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Approaching air buoyancy in aero/cryogel vacuum vessels

Air impermeability has been observed in low-density aerogel and cryogel materials, which has led to a series of experiments to investigate the feasibility of an air buoyant vacuum vessel, as well as the fabrication and testing of sub-buoyant prototypes. Here, bulk samples of silica aerogel were shown to isolate vacuum from ambient air for several hours with optimal vacuum isolation occurring at a density of approximately 85 mg cm –3 . It was demonstrated using polyimide aerogel and cryogel materials that the ability of these foam materials to provide an air impermeable layer between vacuum and atmosphere, in spite of being comprised of mostly void space, is related to material stiffness. It is hypothesized that this behavior is due to local deformation of the random nanostructure of the material. Spherical shell vacuum vessels were produced using the polyimide cryogel, and less than 133 Pa vacuum containment was demonstrated under active pumping. In order to approach the non-buoyant to buoyant transition for these vacuum vessels, a polyimide composite was produced using helical fibers for which preliminary mechanical testing was performed.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Strong interfaces: the key to high strength in nano metallic laminates

Excellent mechanical properties of nanomaterials are usually attributed to their nanoscale feature size and high-density interfaces. This work explores the effects of intrinsic interface properties on mechanical properties of nano metallic laminates (NMLs). We show that the interface strength significantly affects the mechanical properties of NMLs. Via in situ mechanical testing and characterization, we investigate the deformation behavior and concurrent microstructure evolution in NMLs with four types of dissimilar interfaces. Our results show that the strength and deformation behaviors of NMLs are largely determined by interface strength. Strong interfaces can simultaneously increase the strength, work hardening capability, and deformability of NMLs. In conclusion, this work brings new insight into the design of advanced metallic materials through tuning of interface properties.

36 MATERIALS SCIENCE↗
NASA NTRS2017

Reversible and Irreversible Time-Dependent Behavior of GRCop-84

A series of mechanical tests were conducted on a high-conductivity copper alloy, GRCop-84, in order to understand the time dependent response of this material. Tensile, creep, and stress relaxation tests were performed over a wide range of temperatures, strain rates, and stress levels to excite various amounts of time-dependent behavior. At low applied stresses the deformation behavior was found to be fully reversible. Above a certain stress, termed the viscoelastic threshold, irreversible deformation was observed. At these higher stresses the deformation was observed to be viscoplastic. Both reversible and irreversible regions contained time dependent deformation. These experimental data are documented to enable characterization of constitutive models to aid in design of high temperature components.

viscoelasticity↗