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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 1,603 records · Page 89
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Subvoxel Control of Fiber Orientation via Multidirectional Shearing in 3D Printing

Anisotropy, the characteristic of materials exhibiting different properties based on their direction, is widespread in nature. Conventional manufacturing techniques often fall short in recreating such complex anisotropy. While 3D printing allows for precise fiber deposition in anisotropic composites, previous studies have only achieved bulk reorientation of fibers at the voxel level in two dimensions. This limits the replication of localized 3D anisotropies found in natural materials. To address this, a novel 3D printing technique is presented that enables subvoxel control of fiber orientation in all three directions using multidirectional shearing via nozzle rotation and inclination. The fiber orientation control in these experimental tests is driven by a numerical model, enabling a fully digital approach to program microstructures within a strand. This programmability is demonstrated through mechanical and thermal tests, illustrating a localized and controllable response to external stimuli. Achieving such complex anisotropy holds potential across several fields, including wearables and biomedical implants, lightweight composite structures, and energy storage technologies such as batteries and supercapacitors.

3D printing↗
DOE OSTI2019

Dendrite-Free Flexible Fiber-Shaped Zn Battery with Long Cycle Life in Water and Air

Fiber-shaped aqueous rechargeable Zn batteries (FARZBs) show flexibility, good reliability, cost-effectiveness, high energy/power densities, and high safety that have attracted increasing attention as promising energy storage devices for future wearable applications. However, the development of FARZB is limited by its poor cycling life and inferior charge-discharge performance, mainly suffering from zinc dendrite growth and increasing electrode irreversibility. In this work, dendrite-free fiber-shaped Zn//Co 3 O 4 rechargeable batteries with a long cycle life tested in water and air, are obtained via tuning the surface binding energy of Zn on the anode using the zincophilic N,O-functional carbon fiber, as well as engineering the Co 3 O 4 cathode with a nanowire array structure. The fiber-shaped Zn//Co 3 O 4 full battery demonstrates remarkable long cycle life in water and air with high energy density, impressive flexibility, and excellent waterproof ability (fully immersed and charged/discharged under water for more than 33 h for 3000 cycles with capacity retention of ≈80%). The reversible electrochemical mechanisms of the FARZBs, without obvious zinc dendrite deposits and structural change of Co 3 O 4 nanowires, are confirmed by a series of characterizations. Furthermore, these results demonstrate that the FARZBs are promising power sources for emerging wearable electronics.

25 ENERGY STORAGE↗
DOE OSTI2019

Simultaneously tuning dense skin and porous substrate of asymmetric hollow fiber membranes for efficient purification of aggressive natural gas

Highly permeable, selective, and stable asymmetric membranes are required to replace the traditional separation approaches for natural gas purification with higher energy efficiency and smaller footprints. In this work, we report on the design and engineering of defect-free asymmetric hollow fiber membranes with a thin dense skin and highly porous substrate to effectively deal with aggressive natural gas. A crosslinkable polymer with rigid molecular structure and high molecular weight was synthesized for developing spinning dope with desirable solution properties. Phase separation behavior of the polymer was carefully controlled by systematic formulation of the dope composition and optimizing spinning conditions, thereby realizing simultaneously tuning dense skins and porous substrates of the spun asymmetric hollow fiber membranes. The crosslinked hollow fiber membrane, with well-preserved delicate asymmetric nanostructures, exhibited unprecedentedly high and stable separation performance for long-term processing extremely aggressive CO 2 /CH 4 mixtures (with pressure up to 820 psi containing C6(+) hydrocarbons), thereby showing great potential for practical application of natural gas purification. This research provides a new platform to create hollow fiber membranes with both high permeance and plasticization resistance in natural gas service.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Ultra-thin skin carbon hollow fiber membranes for sustainable molecular separations

Here, a transformative platform is reported to derive ultra-thin carbon molecular sieve (CMS) hollow fiber membranes from dual-layer precursor hollow fibers with independently tuned skin layer and substrate properties. These ultra-thin CMS hollow fiber membranes show attractive CO 2 /CH 4 separation factors and excellent CO 2 permeances up to similar to 1,400% higher than state-of-the-art asymmetric CMS hollow fiber membranes. They offer a unique combination of permeance and selectivity competitive with zeolite membranes, yet with much higher membrane packing density and potentially much lower costs.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Non–solvent Fractionation of Lignin Enhances Carbon Fiber Performance

Even though lignin carbon fiber has been sought after for several decades, the poor mechanical performance remains to be a major barrier for commercial applications. The low mechanical performance is attributed to the heterogeneity of lignin polymer. Recent advances in fractionation technologies showed the great potential to reduce lignin heterogeneity, but current fractionation methods often depend on costly chemicals and materials such as enzymes, organic solvents, membranes, and dialysis tubes. Here, a new non–solvent strategy was developed to fractionate lignin by autohydrolysis. By using only water, lignin was efficiently fractionated into water–soluble and –insoluble fractions. The latter fraction had increased molecular weight and uniformity and resulted in more β–O–4 interunitary linkages as analyzed by size–exclusion chromatography and 2D heteronuclear single quantum coherence NMR spectroscopy, respectively. In particular, the water–insoluble fraction significantly enhanced the mechanical performances of the resultant carbon fibers. Mechanistic study by differential scanning calorimetry (DSC) revealed that the miscibility of lignin with guest polyacrylonitrile molecules was improved with the reduced lignin heterogeneity. Crystallite analyses by XRD and Raman spectroscopy revealed that the crystallite size and content of the pre–graphitic turbostratic carbon structure were increased. The fundamental understanding revealed how lignin fractionation could modify lignin chemical features to enhance the mechanical performance of resultant carbon fibers. As a result, the autohydrolysis fractionation thus represents a green, economic, and efficient methodology to process lignin waste and boost lignin carbon fiber quality, which could open new horizons for lignin valorization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Additive manufacturing of sandwich panels with continuous fiber reinforced high modulus composite facings

Abstract An improved approach consisting of a combination of fiber placement and fused filament fabrication is introduced for the additive manufacture (AM) of structural grade sandwich beams. Here, sandwich beams are additively manufactured using in‐situ deposition and consolidation of continuous fiber unidirectional facings made from a commingled yarn system of e‐glass fiber (~50% vol.) and amorphous PET, and a hexagonal honeycomb core structure made from PETG. Both facings and the sandwich core are manufactured on a single machine, in one sequence (skin‐core‐skin), employing the benefit of matrix compatibility to create autohesion at the interfaces. Flexural and transverse shear rigidity are determined experimentally and compared with analytical predictions and show correlation to within 3%. Flexural strength and core shear strength are also measured. Post‐mortem examinations show that core fracture and core facing debond were the dominant failure mode in flexure. Single cantilever beam tests were performed to evaluate core facing debond toughness. Subsequently, surface preheat using infrared heaters was utilized to increase autohesion between core and facing. The results show debond toughness was increased 4 times using infrared heating. This research effort presents a manufacturing approach that has the potential for the AM of stiff, well bonded, structural grade sandwich beams, in an integrated sequence, employing in‐situ consolidation to the facings, without the need for the use of intermediate adhesives for skin‐to‐core bonding. Highlights An improved additive manufacturing technique for making sandwich panels is developed. Sandwich panel facings have fiber volume fractions of approximately 50%. Surface preheat improves core‐to‐facing debond toughness by a factor of 4. Top and bottom facings are consolidated during manufacture leading to better properties. Experimental results are compared to analytical predictions and show good correlation.

17 WIND ENERGY↗
DOE OSTI2019

N-Silylated Benzothiazolium Dye as a Coupling Agent for Polylactic Acid/Date Palm Fiber Bio-composites

This work proposes a benzothiazole derivative bearing a silane moiety as a new coupling agent for polylactic acid (PLA) reinforced by date palm fibers (DPFs). The bio-composites are prepared by solution blending followed by melt compounding. From the samples produced, a complete characterization is performed including morphological, mechanical and thermal properties as a function of fiber content. The results show that the proposed fiber treatment is an easy and effective method to improve the interfacial properties and fiber dispersion leading to better material performance. For example, the addition of only 1 wt% of the dye–IPTMS to the bleached DPF not only improved the thermal stability of the biocomposites, but also led to a significant increase of the Young’s modulus at 7 wt% and higher torsion modulus up to 5 wt% (optimum value).

36 MATERIALS SCIENCE↗
DOE OSTI2019

Multiwavelength erbium-doped fiber laser based on a polarization-dependent in-line Mach–Zehnder interferometer

A multiwavelength erbium-doped fiber laser based on a polarization-dependent in-line Mach–Zehnder Interferometer (in-line MZI) is proposed and experimental demonstrated. The polarization-dependent in-line MZI demonstrated is constructed by sandwiching a length of polarization maintaining fiber (PMF) between two abrupt fiber tapers fabricated in SMF. The proposed in-line MZI can work as a cost-effective all-fiber-based polarizer. In combination with the nonlinear polarization rotation technique, stable multiwavelength laser comb with uniform wavelength spacing is achieved at room temperature. The wavelength spacing is 0.8 nm. By properly tuning the PCs, the output laser combs with double and triple channel spacing can be also obtained.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Numerical Study and Experimental Validation of Effect of Varying Fiber Crack Density on Stiffness Reduction in CFRP Composites

Representative volume element (RVE) has commonly been used to predict the stiffness of undamaged composite materials using finite element analysis (FEA). However, never has been an independently measured true microstructural damage quantity used in FEA to predict composite stiffness. Hence, in this work, measured fiber crack density in unidirectional fiber composite (generated using controlled fatigue loading) was used to predict reduction in stiffness using a RVE. It was found that the stiffness changes with change in depth of the volume element along the fiber direction and asymptotically reaches a constant value beyond a critical length called representative depth. It was argued that this representative depth should be more than the minimum of two characteristic length scales, twice of ineffective length and average length of broken fibers. Effective stiffness obtained from FEA of the optimum-sized RVE was in excellent agreement with the experimental results for given microstructural damage state.

36 MATERIALS SCIENCE↗
DOE OSTI2016

High-entropy Al 0.3 CoCrFeNi alloy fibers with high tensile strength and ductility at ambient and cryogenic temperatures

High-entropy alloys (HEAs) are multi-component systems based on novel alloy composition designs with entropy maximization. They feature an array of unique mechanical properties when compared with traditional alloys. In this study, HEA fibers with diameters ranging from 1 to 3.15 mm in diameter, with the composition of Al 0.3 CoCrFeNi (atomic percent, at.%), were successfully fabricated by hot-drawing, followed by microstructural characterization using scanning-electron microscopy (SEM) and transmission-electron microscopy (TEM). The compositional variations within and between fibers were determined using energy-dispersive X-ray spectroscopy in TEM along with atomic-probe tomography (APT). These analyses revealed a homogeneous face-centered cubic (FCC) structure in the as-cast material, while post processing (e.g., forging and wire drawing) produced nanosized B2 particles in an FCC matrix. Electron back-scatter diffraction (EBSD) was used to determine the evolution of the texture and grain boundary character after processing of the fibers. The tensile strength and plasticity of the fibers were determined at both 298 K (1207 MPa/7.8%) and 77 K (1600 MPa/17.5%). Detailed TEM analyses revealed that the improvement of mechanical properties at 77 K (i.e. increased strength and ductility) is due to a change in deformation mechanisms from the planar slip of dislocations to nano-twinning. Such properties could be beneficial for cryogenic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Transgenic mice expressing mutant Pinin exhibit muscular dystrophy, nebulin deficiency and elevated expression of slow-type muscle fiber genes

Highlights: •Pnn CCD domain functions as a dominant negative mutant regulating Pnn expression and function. •Pnn CCD mutant Tg mice have a muscle wasting phenotype during development and show dystrophic histological features. •Pnn mutant muscles are susceptible to slow fiber type gene transition and NEB reduction. •The Tg mouse generated by overexpression of the Pnn CCD domain displays many characteristics resembling NEB{sup +/−} mice. -- Abstract: Pinin (Pnn) is a nuclear speckle-associated SR-like protein. The N-terminal region of the Pnn protein sequence is highly conserved from mammals to insects, but the C-terminal RS domain-containing region is absent in lower species. The N-terminal coiled-coil domain (CCD) is, therefore, of interest not only from a functional point of view, but also from an evolutionarily standpoint. To explore the biological role of the Pnn CCD in a physiological context, we generated transgenic mice overexpressing Pnn mutant in skeletal muscle. We found that overexpression of the CCD reduces endogenous Pnn expression in cultured cell lines as well as in transgenic skeletal muscle fibers. Pnn mutant mice exhibited reduced body mass and impaired muscle function during development. Mutant skeletal muscles show dystrophic histological features with muscle fibers heavily loaded with centrally located myonuclei. Expression profiling and pathway analysis identified over-representation of genes in gene categories associated with muscle contraction, specifically those related to slow type fiber. In addition nebulin (NEB) expression level is repressed in Pnn mutant skeletal muscle. We conclude that Pnn downregulation in skeletal muscle causes a muscular dystrophic phenotype associated with NEB deficiency and the CCD domain is incapable of replacing full length Pnn in terms of functional capacity.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Increasing ethanol yield through fiber conversion in corn dry grind process

Conversion of corn fiber to ethanol in the dry grind process could increase ethanol yields, reduce downstream processing costs and improve overall process profitability. In this work, we investigate the in-situ conversion of corn fiber into ethanol (cellulase addition during simultaneous saccharification and fermentation) during dry grind process. Addition of 30 FPU/g fiber cellulase resulted in 4.6% increase in ethanol yield compared to the conventional process. Use of excess cellulase (120 FPU/g fiber) resulted in incomplete fermentation and lower ethanol yield compared to the conventional process. Lastly, multiple factors including high concentrations of ethanol and phenolic compounds were responsible for yeast stress and incomplete fermentation in excess cellulase experiments.

09 BIOMASS FUELS↗
DOE OSTI2025

Structure-property relationships and recyclability of natural fiber insulation

Thermal insulation can significantly decrease the energy required to maintain internal temperatures within buildings, saving money and decreasing environmental impacts. Many industrially available insulation options utilize petroleum-derived materials, such as polyurethane, fiberglass, and polystyrene, which can be detrimental to the environment by emitting greenhouse gases during production. A sustainable alternative to these synthetic insulations is the use of renewable feedstocks to produce comparable insulation products. In this work, natural fibers such as flax and banana were bound with an epoxy system to produce natural-fiber insulation. Key experimental parameters for this study included evaluating the fiber lengths and processing methods while varying the viscosity of the epoxy binder solvent dissolution. Insulation performance was determined by comparing density, thermal conductivity, resilience, and compressive strength; these parameters were tested to further understand and investigate the structure- property relationships within the system and to understand how these composites compare to current commercial materials. Furthermore, from this characterization and optimization, a natural fiber sample with an R/in. >5 was achieved, making these materials competitive with commercial alternatives.

Compressive strength↗
DOE OSTI2024

Mesophase pitch-based high performance carbon fiber production using coal extracts from mild direct coal liquefaction

Mild direct coal liquefaction (autogenous pressure, no catalyst, no H2 gas) of Springfield coal in fluid catalytic cracking decant oil is shown to effectively produce coal extract precursors to spinnable mesophase pitch. Here this work demonstrates that the coal extract can be thermally treated to obtain mesophase pitch in a facile one-step process, bypassing the production of an intermediate isotropic pitch. Furthermore, the presence of 25 wt.% coal in the initial slurry can increase the yield to mesophase pitch nearly twofold and yield to carbon fiber by approximately 70%. The coal extract-derived mesophase pitch was melt-spun and heat treated to produce carbon fiber with graphitic texture, high modulus (>400 GPa) and tensile strength up to 943 MPa. Overall, this work demonstrates that coal can be effectively utilized to markedly amplify the mesophase pitch and carbon fiber yield from fluid catalytic cracking decant oil by relatively simple processing, while conserving utility as a precursor to high performance carbon fiber and potentially other high value graphitic products.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Innovative large overbraided carbon fiber composite beams in historical Friendship Bell Pavilion

The International Friendship Bell Pavilion located in the City of Oak Ridge, Tennessee symbolizes the spirit of the peace and friendship shared by the city of Oak Ridge and city of Naka, Japan. The Bell Pavilion features an 8000-pound bronze cast bell along with futuristic materials and advanced manufacturing technologies. The team has developed innovative overbraided carbon fiber arched beams in conjunction with the bronze bell. Carbon fiber was utilized in these beams because of its lightweight, strong, stiff, and durable characteristics. A sandwich design used a high-performance foam core, overbraided with triaxial carbon fibers. This is the world’s largest overbraided composite structure for parks and recreation. For the first time in such an application, 17 free floating, 33-foot (10 m) long arched carbon fiber composite beams cantilever from a central concrete-steel superstructure over the bronze bell. The arc radius of the bottom of each beam is uniquely different giving an appearance of an open dome when standing underneath the structure.

Parks and Recreation↗
DOE OSTI2015

Effect of twist on transverse impact response of ballistic fiber yarns

A Hopkinson bar was employed to conduct transverse impact testing of twisted Kevlar KM2 fiber yarns at the same impact speed. The speed of Euler transverse wave generated by the impact was measured utilizing a high speed digital camera. The study included fiber yarns twisted by different amounts. The Euler transverse wave speed was observed to increase with increasing amount of twist of the fiber yarn, within the range of this investigation. As a result, the higher transverse wave speeds in the more twisted fiber yarns indicate better ballistic performance in soft body armors for personal protection.

42 ENGINEERING↗
DOE OSTI2021

An approach to identifying fibers and evolved compounds from flame resistant fabrics

Flame resistant (FR) fabrics have use in civilian, military, and industrial applications. Herein, this work describes the development of a methodology aimed at identifying the fiber composition of blended fabrics of unknown composition. Here, FR fabrics used in military uniforms, are studied using a combination of X-ray photoelectron spectroscopy (XPS), isothermal thermogravimetric analysis (TGA) and pyrolysis gas chromatography/mass spectrometry (Py-GC-MS). Elemental analysis of the fabrics using XPS yielded a preliminary determination of the composition of the polymer(s) and aided in the identification of FR additives. TGA and Py-GC-MS experiments were used for subsequent compound identification. In TGA the temperature of mass loss events was compared to reference materials, and in Py-GC-MS the pyrolysis products of the blended FR fabrics were compared to those from a series of potential parent fibers. It was possible to discern the composition of the parent fibers and the type of FR treatment added to fabrics because the thermal decomposition chemistry did not significantly change by blending the fibers to make fabrics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Modifying the strength and strain concentration profile within collagen scaffolds using customizable arrays of poly-lactic acid fibers

Here, the tendon-to-bone junction is a highly specialized tissue which dissipates stress concentrations between mechanically dissimilar tendon and bone. Upon injury, the local heterogeneities across this insertion are not regenerated, leading to poor functional outcomes such as formation of scar tissue at the insertion and re-failure rates exceeding 90%. Although current tissue engineering methods are moving towards the development of spatially-graded biomaterials to begin to address these injuries, significant opportunities remain to engineer the often complex local mechanical behavior of such biomaterials to enhance their bioactivity. Here, we describe the use of three-dimensional printing techniques to create customizable arrays of poly-lactic acid (PLA) fibers that can be incorporated into a collagen scaffold under development for tendon bone junction repair. Notably, we use additive manufacturing concepts to generate arrays of spatially-graded fibers from biodegradable PLA that are incorporated into collagen scaffolds to create a collagen-PLA composite. We demonstrate the ability to tune the mechanical performance of the fiber-scaffold composite at the bulk scale. We also demonstrate the incorporation of spatially-heterogeneous fiber designs to establish non-uniform local mechanical performance of the composite biomaterial under tensile load, a critical element in the design of multi-compartment biomaterials for tendon-to-bone regeneration applications. Together, this work highlights the capacity to use multi-scale composite biomaterials to control local and bulk mechanical properties, and provides key insights into design elements under consideration for mechanically competent, multi-tissue regeneration platforms.

3D printing↗