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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Interpretation of wide-angle x-ray diffraction patterns from mesophase pitch-based carbon fibers – a simulation and experimental study

Carbon fiber is a critical material in a wide range of industries, where it is highly valued for its high specific strength/stiffness, excellent wear resistance, efficient electrical and thermal transport properties, chemical resistance, and low coefficient of thermal expansion. The properties of a specific carbon fiber are closely tied to its structural characteristics at all length scales. Here, in this work, we applied wide-angle x-ray diffraction to a set of heat-treated mesophase pitch-based carbon fibers, with the goal of elucidating the crystalline structures as a function of fiber orientation. To assist with analysis and interpretation of the experimental data, we employed diffraction pattern simulations using the scalar and vector forms of the Debye scattering equation to determine the influence of basal plane orientation, crystalline ordering (turbostratic-graphitic), and basal plane asymmetry on the diffraction patterns. The results presented here suggest that growth of the transverse crystallites in mesophase pitch-based carbon fiber is fixed until graphitization temperatures are reached. The work completed here provides a framework for the analysis of carbon fiber and other oriented carbon-based materials via diffraction.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Evaluating consumer 3D printing nozzles as a low cost alternative for mesophase pitch-derived carbon fiber production

Synthetic fibers, such as Kevlar fibers, SiC fibers, and carbon fibers, are essential components for constructing high performance structures. Whether for engineering, sports, energy storage (batteries and supercapacitors), or aerospace applications, fiber microstructure plays a critical role in fiber properties and functionalities. However, studying fiber nozzle configurations and spinning parameters to achieve the desired microstructure remains challenging, costly, and time consuming. Here, mesophase pitch-derived fibers were used as an example to demonstrate that low cost, commercially available 3D printer nozzles can “print” fibers. Four different nozzles were used to “print” fibers and the effects of their features on fiber properties were observed and compared to other lab spun and commercial pitch- derived CF. A longer orifice length resulted in higher modulus fiber whereas a larger draw-down ratio yielded a stronger fiber. Furthermore, the findings provide a new opportunity for 3D printer hardware application and open up opportunities for developing low-cost fibers.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Enhanced Interfacial Strength in Carbon Fiber Composites via Mussel‐Inspired Sizing Polymers

Composite materials possess a high strength-to-weight ratio. A key determinant of their mechanical performance is the interfacial strength between the fibers and the matrix. Sizing agents are commonly used to improve this interface by promoting better adhesion, though optimizing this interaction remains a significant challenge. Here, this study evaluates the use of poly(catechol-styrene) (PCS), a mussel-inspired sizing agent, to enhance fiber–matrix bonding in carbon fiber composites. Woven carbon fiber laminates were dip-coated with varying concentrations of PCS (0.05 and 0.1 wt%) and subsequently fabricated using vacuum-assisted resin transfer molding followed by compression molding. Interlaminar shear strength (ILSS) tests showed improvements of 4% and 8% for the 0.05% and 0.1% PCS treatments, respectively. These results indicate that PCS is effective in reinforcing interfacial adhesion, thereby improving the mechanical integrity of carbon fiber-reinforced composites.

Carbon fiber composites↗
DOE OSTI2022

Carbon fibers derived from commodity polymers: A review

Carbon fiber composites are prohibitively expensive for a wide array of applications that would greatly benefit from their superior specific strength and specific stiffness. Replacing the market-dominant carbon fiber precursor material, polyacrylonitrile, with a low-cost alternative would significantly reduce the cost of carbon fiber production. Commodity polymers may provide such an alternative thanks to their abundance and ease of production into fibers. Furthermore, this review presents state-of-the-art carbon fiber production from polyacrylonitrile, an overview of melt-spinnable alternative precursors broadly, and an in-depth review of the latest advances in the synthesis of carbon fibers from low-cost, commodity thermoplastics such as polyethylene, polyamide, polystyrene, polyester, and poly(vinyl chloride).

36 MATERIALS SCIENCE↗
DOE OSTI2023

Performance of hybrid Innegra-carbon fiber composites

Abstract In this work material synergy with high stiffness carbon fiber with ductile high strength polypropylene fiber (Innegra S), (referred to as Innegra, herein) have been evaluated in a range of laminate designs. Both woven and discontinuous carbon fiber have been considered. The discontinuous fibers are based on three-dimensional deposition (3DEP) (referred to as 3DEP, herein) carbon fiber preform process. Eleven (11) variants of Innegra-carbon fiber hybrid laminates were investigated for tensile, flexure, compression, in-plane shear and low velocity impact response. The effect of position of Innegra within the laminate was studied and found to influence strength and stiffness properties. In terms of overall trends, Innegra provides upward of 18% improvement in strain (ductility) to the composite and eliminates brittle fracture of carbon fiber. The moduli trends follow the proportionality of Innegra fiber to carbon fiber plies. However, the strength is controlled by the interface between Innegra and carbon fiber. The primary failure mode in tension and compression is via onset of debonding between Innegra and carbon fiber. The 3DEP carbon fiber constituents provided highest values of in-plane shear indicating that three-dimensional (3D) network of carbon fiber provides higher shear resistance. The Innegra intensive variants exhibited superior energy absorption under low velocity impact, at energy levels 15–60 J. This work provides insight for designers to incorporate Innegra and carbon fiber hybrids in composite structures.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Enhancing functionalities in carbon fiber composites by titanium dioxide nanoparticles

Carbon fiber composite's high specific strength makes it incredibly useful for structural applications. However, their low strain-to-failure can be problematic in structural applications that can potentially see high strain conditions or high fatigue cycles resulting in sudden, catastrophic failure. This is further complicated by damage manifesting within the composite thus not showing damage indicators on the surface. Therefore, monitoring the structural integrity and strain history of the composite in application by itself—while maintaining positive composite performance—is vital to ensure safe operation. In this study, a homogeneous dispersion of TiO 2 nanoparticles on carbon fiber is demonstrated to generate a piezoresistive carbon fiber polymer matrix composite with enhanced self-sensing capabilities. The nanoparticle-embedded composites also exhibited superior strength and damping potential compared to the nanoparticle-free composites. The apparent interlaminar shear strength increased by up to 15% and the damping loss factor increased by an average of 150% while the piezoresistive sensitivity increased by up to 180% with the addition of a small weight fraction of nanoparticles to the fiber surface. These results demonstrate an approach to simultaneously improve the sensing capabilities, damping behavior and mechanical strength of carbon fiber composites by simply adding nanoparticles in the fiber sizing using a commercially scalable deposition method.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Development of a Lower Cost, High Volume, Commercially Available, Precursor for Lower Cost Carbon Fiber for Automotive and Wind Blade Applications

Essentially all carbon fibers used in structural applications are presently manufactured from solution spun polyacrylonitrile (PAN) precursor. Solution spinning is accomplished at relatively low temperatures using very large amounts of environmentally unfriendly solvents that impart major impact to line speed and costs involved with handling and reclaiming the solvents and associated “waste streams” required in spinning and extracting those solvents. Dralon and others have demonstrated the dry spinning of PAN in the production of some acrylic fibers for textile applications, but to this point it has not been demonstrated in the production of carbon fibers. In dry spinning, the PAN polymer is also dissolved into similar solvents, although typically less solvent is utilized to maintain a somewhat higher solids content of 20-50%. The use of lower overall solvent quantities and elimination of the need for solvent/water separation simplifies and reduces the cost of solvent recovery operations. Other portions of the precursor production and carbon fiber manufacturing processes are quite similar. The work described in this report demonstrated that dry spun acrylic fiber can be an attractive candidate for carbon fiber precursor of potential interest to applications looking to capture the specific stiffness (stiffness per unit mass) and specific strength (strength per unit mass) of carbon fiber when produced at a discount relative to commercial carbon fibers in the market today. Dralon has determined that the dry spinning process utilized for producing fibers used as precursors in this project requires 27% less energy versus producing comparable fibers via the industry standard wet spinning process. Identification of carbon fiber manufacturers, as well as applications development and targeted marketing, will be required to achieve significant in-roads into mission areas of interest to DOE, such as automotive applications and wind turbine blades. In support of that activity, initial data produced in this project indicate the innovative approach as described in this report can meet at least the baseline property requirements identified for these applications.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Method of producing carbon fibers from multipurpose commercial fibers

A method of producing carbon fibers includes the step of providing polyacrylonitrile precursor polymer fiber filaments. The polyacrylonitrile precursor filaments include from 87-97 mole % acrylonitrile, and less than 0.5 mole % of accelerant functional groups. The filaments are no more than 3 deniers per filament. The polyacrylonitrile precursor fiber filaments can be arranged into tows of at least 150,000 deniers per inch width. The arranged polyacrylonitrile precursor fiber tows are stabilized by heating the tows in at least one oxidation zone containing oxygen gas and maintained at a first temperature T1 while stretching the tows at least 10% to yield a stabilized precursor fiber tow. The stabilized precursor fiber tows are carbonized by passing the stabilized precursor fiber tows through a carbonization zone. Carbon fibers produced by the process are also disclosed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Method of producing carbon fibers from multipurpose commercial fibers

A method of producing carbon fibers includes the step of providing polyacrylonitrile precursor polymer fiber filaments. The polyacrylonitrile precursor filaments include from 87-97 mole % acrylonitrile, and less than 0.5 mole % of accelerant functional groups. The filaments are no more than 3 deniers per filament. The polyacrylonitrile precursor fiber filaments can be arranged into tows of at least 150,000 deniers per inch width. The arranged polyacrylonitrile precursor fiber tows are stabilized by heating the tows in at least one oxidation zone containing oxygen gas and maintained at a first temperature T1 while stretching the tows at least 10% to yield a stabilized precursor fiber tow. The stabilized precursor fiber tows are carbonized by passing the stabilized precursor fiber tows through a carbonization zone. Carbon fibers produced by the process are also disclosed.

Naskar, Amit K.↗
DOE OSTI2023

Unveiling the microstructural evolution of carbon fibers derived from polyamide-6

Polyacrylonitrile-based carbon fibers have dominated the industry for decades, but the high cost of polyacrylonitrile has prevented the widespread adoption of carbon fiber in high-volume structural applications. As such, a significant amount of research has been dedicated to finding an alternative, low-cost carbon fiber precursor. In this work, carbon fibers were produced from polyamide-6 using metal salt impregnation and a thermo-oxidative stabilization step. To gain further insight into the carbonization process and microstructural transformation, the morphologies, crystallinities, elemental compositions, and thermal stabilities of the fibers were characterized at various stages of processing. The stabilization step resulted in a significant increase in carbon yield, indicating a dramatic increase in thermal stability. This is due to the crosslinking of polyamide-6 chains, which was confirmed by functional group analysis. The crystallinity of the fibers was also significantly altered during processing, as the produced carbon fibers consisted of pseudo-amorphous carbon with two distinct regions of metal salt impregnation. Finally, the findings and microstructural evolution mechanisms provide guidelines for further research into carbon fiber produced from polyamide-6.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Radiation damage of a two-dimensional carbon fiber composite (CFC)

Carbon fiber composites (CFC) are, among other applications, already in use as low-impedance collimating elements for intercepting TeV-level protons machines, like the CERN Large Hadron Collider. Towards a comprehensive understanding of these materials’ properties and behavior, a series of radiation damage campaigns have been undertaken in order to quantitively investigate the response of AC-150 K CFC to high proton fluences. The CFCs dimensional changes, stability, micro-structural evolution, and structural integrity below and above 5 × 10 20 p/cm 2 fluence threshold were studied. The irradiating particles were protons of kinetic energies in the range of 130–200 MeV. The effects of the irradiation temperature (~90–180°C and 280–500°C) combined with the proton fluence on the dimensional stability and the microstructural evolution of this anisotropic two-dimensional composite structure were studied using precision dilatometry and X-ray diffraction. Our results shed light on the fluence-based limitations for these composite materials. Furthermore, we compare these results with reference unirradiated graphite, and we discuss the similarities and differences in the dimensional changes and post-irradiation annealing properties.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Computational investigations of Dienes defect- and vacancy-induced changes in the electronic and vibrational properties of carbon fiber structural units

Carbon fiber (CF) is a promising lightweight alternative to steel and is of significant interest for energy applications. As CF continues to find new uses and is exposed to new external conditions, a noninvasive method of monitoring its structural integrity is critical. Raman spectroscopy is a commonly used method for this monitoring; however, it is highly inferential, and the interpretation of the data is not always straightforward. In this work, we perform density functional theory (DFT) calculations to investigate changes in the vibrational properties of CF structural units (i.e., graphene and graphite) caused by monovacancy and Dienes defects as a foundation for modeling more complex defects that move our model toward that of realistic CF. Using large computational supercells, we can understand how these defects change the electronic structure and vibrational properties of graphene and graphite for interdefect distances near those of the lower experimental limit. The monovacancy opens an electronic bandgap at the K point. Although no such electronic gap is opened by the Dienes defect, both defects introduce flat defect bands near the Fermi energy. The Dienes defect creates long-range deviations of the phonons, leading to substantial broadening of the highest frequency optical modes in the band structure compared to that of the pristine material. In contrast, the phonon changes caused by the monovacancy are short range, and only minor changes in the band structure or phonon density of states were observed. These findings can assist in the interpretation of experimental results by providing atomic-scale insight into key electronic and vibrational features.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Additive manufacturing of two-phase lightweight, stiff and high damping carbon fiber reinforced polymer microlattices

Carbon fiber reinforced polymer (CFRP) composite is known for its high stiffness-to-weight ratio and hence is of great interest in several engineering fields such as aerospace, automotive, defense, etc. However, such a composite is not suitable for energy dissipation as failure occurs with very little or no plastic deformation. Herein, we present an extendable multi-material projection microstereolithography process capable of producing carbon-fiber-reinforced cellular materials that achieve simultaneously high specific stiffness and damping coefficient. Inspired by the upper bounds of stiffness-loss coefficient in a two-phase composite, we designed and additively manufactured CFRP microlattices with soft phases architected into selected stiff-phase struts. Our results, confirmed by experimental and analytical calculations, revealed that the damping performance can be significantly enhanced by the addition of only a small fraction of the soft phase. The presented design and additive manufacturing strategy allow for optimizing mutually exclusive properties. As a result, these CFRP microlattices achieved high specific stiffness comparable to commercial CFRP, technical ceramics, and composites, while being dissipative like elastomers.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Solid composites containing polymeric matrix with carbon fibers embedded therein

A functionalized carbon fiber having covalently bound on its surface a partially cured epoxy or amine-containing sizing agent, wherein at least a portion of epoxide or amine groups in the sizing agent are available as uncrosslinked epoxide or amine groups, which corresponds to a curing degree of epoxide or amine groups of no more than about 0.6. Composites comprised of these functionalized carbon fibers embedded in a polymeric matrix are also described. Methods for producing the functionalized carbon fibers and composites thereof are also described.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Permeability simulation of kidney-bean shaped carbon fibers

Cost saving efforts in carbon fiber manufacturing may result in irregularly shaped cross-sections, often as a kidney-bean shape. Here, in this research, flow simulations were performed to determine transverse permeability of these kidney-bean shaped fibers. Three different unit-cell packing arrangements for the kidney-bean shaped fibers and unit-cell orientations of 0°, + 90°, and – 90° were considered over the fiber volume fraction range 0.30 – 0.75. The kidney-bean shaped fibers had two distinct hexagonally packed unit-cell geometries because of the fiber’s asymmetry with different packing efficiency. The maximum fiber packing fraction for kidney-bean shaped fibers was 0.923, which was larger than the 0.907 for circular fibers. When compared to circular fibers with hexagonal packing, the kidney-bean shaped fibers had up to a 74% reduction in permeability. The ±90° orientations for KB-fibers with hexagonal packing had an infiltration time up to 3.86 longer than the hexagonal packed circular fibers for the same volume fraction.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Mechanical Properties of High-Temperature Fiber-Reinforced Thermoset Composites with Plain Weave and Unidirectional Carbon Fiber Fillers

Fiber-reinforced thermoset composites are a class of materials that address the arising needs from the aerospace and hypersonic industries for high specific strength, temperature-resistant structural materials. Among the high-temperature resistant thermoset categories, phenolic triazine (PT) cyanate esters stand out thanks to their inherent high degradation temperature, glass transition temperature, and mechanical strength. Despite the outstanding properties of these thermosets, the performance of carbon fiber composites using PT cyanate esters as matrices has not been thoroughly characterized. This work evaluated PT and carbon fiber composites’ compressive properties and failure mechanisms with different fiber arrangements. A PT resin with both plain weave (PW) and non-crimped unidirectional (UD) carbon fiber mats was analyzed in this research. Highly loaded thermoset composites were obtained using process temperatures not exceeding 260 °C, and the composites proved to retain compressive strength at temperatures beyond 300 °C. Compressive testing revealed that PT composites retained compressive strength values of 50.4% of room temperature for UD composites and 61.4% for PW composites. Post-compressive failure observations of the gage section revealed that the mechanisms for failure evolved with temperature from brittle, delamination-dominant failure to shear-like failure promoted by the plastic failure of the matrix. This study demonstrated that PT composites are a good candidate for structural applications in harsh environments.

Hall, Samuel Ernesto↗
DOE OSTI2020

Low cost textile-grade carbon-fiber epoxy composites for automotive and wind energy applications

Carbon fiber reinforced polymer composites are highly desirable for automotive and wind energy applications due to advantages associated with weight reduction, high stiffness and strength, durability, and recyclability. The high cost of carbon fiber has been a limiting factor in its widespread adoption in non-aerospace applications. A low cost (estimated < $11 per kg) wide tow (450-600k) carbon fiber derived from textile grade polyacrylonitirile precursor, and hence called Textile Grade Carbon Fiber (TCF) is introduced in this paper. Fundamental aspects of the TCF are discussed along with a detailed characterization of its mechanical properties. Two manufacturing processes relevant to automotive and wind energy applications are considered, namely-compression molding and resin infusion. Furthermore, at various stages the TCF has been compared to commercial non-aerospace 50k carbon fiber composite. Detailed physical and mechanical properties including tensile, flexural, compression, and interlaminar shear properties are reported and compared to non-aerospace carbon fiber composite. The results provide a means for designers and end-users in the automotive and wind energy sector to consider different forms of economical non-aerospace carbon fibers.

42 ENGINEERING↗