Graphite Fiber-reinforced Composites Research Articles

Radiator production for Pylon Fission Surface Power System through lunar In-Situ Resource Utilization

Background Fission Surface Power (FSP) is currently being considered by NASA for future lunar exploration and Ultra-Safe Nuclear Corporation (USNC) is developing their Pylon FSP system. Methods This paper introduces the system focusing on the materials used for its main components. It also analyses the lunar availability of the elements required to produce these components and suggests that In-Situ Resource Utilization (ISRU) should be considered. Results As a result of the conducted analysis, it is concluded that since mass is the most important parameter when launching payload from Earth, the Pylon component with the largest mass should be considered further. The heaviest system component is the power system which, however, consists of many other components that are made from various materials. The second heaviest component is the radiator made of Titanium (Ti) metal heat pipes and Graphite Fiber Reinforced Composite (GFRC) face sheets with water as the working fluid. Since the production of Ti metal on the Moon is non-economical, Aluminum (Al) metal utilized for the International Space Station (ISS) is considered. Lunar infrastructure required to produce Al using ISRU is already available. Further analysis will be conducted in the future to look into laser 3D printing technologies. Lunar Resources Inc. is already developing techniques for Al extraction from regolith for the production of Al wires. Conclusions This research shows that all the required technologies already exist, and the next step will be to identify how the obtained Al can be manufactured into radiators. It will also be important to identify how much of the total radiator mass is Al metal to increase the fidelity of this analysis Future research will find the break-even point between the Pylon Ti radiators launched from Earth and the production of Al radiators on the Moon.

Free vibration analysis of hybrid laminated plates containing multilayer functionally graded carbon nanotube-reinforced composite plies using a layer-wise formulation

This paper studies the free vibration behavior of hybrid laminated plates using a layer-wise formulation. The laminated structures are made of graphite fiber-reinforced composite (GFRC) and multilayer functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plies. The internal single-walled carbon nanotubes (SWCNTs) are distributed in layer-wise form along the ply thickness direction either uniformly or functionally graded according to four separate patterns. Both the linear and nonlinear of the CNTs distributions form are considered. Theatrical formulations are based on the first-order shear deformation theory (FSDT), and finite element method is employed to obtain the nondimensional natural frequency. The elastic modulus of both GFRC and CNTRC plies composed the hybrid laminated plate is obtained by a micromechanics model. Initially, the provided results are validated by comparing it with the literature; thereafter, a parametric study is carried out the influences of laminates configuration, number of CNTRC plies layers, CNT volume fraction, CNT distribution patterns, linear and nonlinear distribution of CNTs, plate width-to-thickness ratio, plate aspect ratio, boundary conditions, stacking sequences, and number of plies on the free vibration behavior of hybrid laminated plates. Some final remarks considering the laminated plate configuration and the distribution form of the CNT fillers are presented in order to provide a useful observation on the design criteria of the laminated composite plate structures.

Effective Thermal Conductivity and Thermal Contact Conductance of Graphite Fiber Composites

The transverse and longitudinal effective thermal conductivity and contact conductance of discontinuous and misoriented graphite fiber-reinforced composites has been studied over a range of temperatures (20-200°C) and pressures (172-1720 kPa). Three different fiber types (DKE X, DKA X, and K22XX) and three fiber volume fractions (55, 65, and 75%) in a cyanate ester matrix were studied. The addition of fibers to the matrix resulted in an increase in effective thermal conductivity, but appears to level off at fiber volume fractions of 65%. Furthermore, the effective thermal conductivity in the longitudinal direction was significantly greater than in the transverse direction and was more dependent on temperature. These data were used to develop an equation relating the thermal contact conductance to the harmonic mean thermal conductivity of the fiber and matrix material, fiber volume fraction, sample thickness, and microhardness

High-Performance Directional Metallopolyamides. I. Synthesis and Thermal Analysis

High-performance polyamides containing the 4,4′-disubstituted-2,2′-bipyridyl moiety were synthesized by phosphorylation polycondensation from 2,2′-bipyridyl-4,4′-dicarboxylic acid and a series of primary aromatic diamines with triphenylphosphite and pyridine as the agents to facilitate condensation. Polyamides exhibiting improved solubility in organic solvents and strong acids, melting transitions at low temperatures, and good thermal properties were prepared by introducing bulking methyl and fluoro groups and flexible ether and propyl linkages and by using monomers with reduced symmetry. Solutions of the polyamides with rigid main chains (III, IV, V, VI, and VIII) showed birefringence (colorful spherulites) at concentrations of 5, 10, and 15% (w/v) polymer/solvent. The chelation of ruthenium(II) ions resulted in the preparation of directional metallopolyamide systems based on the geometrically favorable tris(2,2′-bipyridyl)ruthenium(II) complex. The three-dimensional polyamides, which absorbed at a λ max of 476 mm and emitted at a λ max of 620 nm, exhibited a high thermal stability and improved solubility, making them suitable candidates for compressive strength studies and cyclic voltammetry studies as part of an effort to address the corrosion of graphite fiber-reinforced composites.

Characterization of the Fiber-Matrix Interphase and its Influence on Mechanical Properties of Unidirectional Composites

The fiber-matrix interphase is commonly altered in graphite fiber rein-forced composites by changing the level of surface treatment imparted to the fibers and by using different fiber sizings. In this study, the influence of both surface treatment and fiber sizing on the mechanical properties of unidirectional composites was studied. Three material systems having the same high modulus Apollo carbon fibers (manufactured by Courtoulds Research) and HC 9106-3 toughened epoxy matrix, but with different fiber sizing and surface treatment, were used to study the effects of the interphase. For convenience, these are designated 810 A, 820 A and 8100 systems. The fibers used in the 810 A and 8100 systems received 100% industry standard surface treatment, while the fibers used in the 820 A system received 200% industry standard surface treatment. The "A" and "O" represent unreacted bisphenol-A epoxy and polyvinylpyrrolidone (PVP) sizing respectively. The formation of distinctly different interphase in these three material systems was confirmed using a pernanganic etching technique. The etching study also revealed a highly nonuniform distribution of PVP in the 8100 system. Unidirectional tensile test results indicated significant reduction in the longitudinal stiffness of the PVP sized 8100 laminates. However, the tensile strength and failure strain of this system were vastly greater than those of the epoxy sized 810 A laminates. The systems with 10% and 200% levels of fiber surface treatment had similar longitudinal tensile properties. Transverse tensile test results indicated that the interracial bond strength was greatest in the 820 A system and lowest in the PVP sized 8100 system. The transverse flexural strength of the 8100 and 820 A systems were however found to be significantly greater than that of the 810 A system. It is postulated that the differences in unidirectional mechanical properties in these material systems are essentially due to differences in the interfacial bond strength and efficiency of load transfer from the matrix to the fiber.

Graphite Fiber/Polyimide Composites with Improved Processability

AbstractIn an effort to improve the processing characteristics of addition-type polyimide matrix resins, the use of flexibilized three-ring and four-ring aryl diamines was investigated. A series of fourteen diamines containing carbonyl and methylene, as well as thio connecting groups was synthesized. The diamines were polymerized with the dimethyl ester of 3,3,′4,4′-benzophenonetetracarboxylic acid, using the monomethyl ester of nadic acid as an end cap. The effect of diamine structure on the solubility and rheological properties during cure, as well as glass transition temperature and thermooxidative stability of neat resins was determined. Graphite fiber-reinforced composites were fabricated from selected resin formulations, and composite thermomechanical properties were investigated.

HYGROTHERMAL STRESS IN A PLATE SUBJECTED TO ANTISYMMETRIC TIME-DEPENDENT MOISTURE AND TEMPERATURE BOUNDARY CONDITIONS

When the temperature and/or moisture at the surfaces of a composite change suddenly, stresses will arise in the composite owing to the nonuniform diffusion of heat and moisture. Recent investigations have shown that under certain conditions the classical uncoupled theory of diffusion can significantly underestimate the coefficient of diffusion. The coupling between heat and moisture is an inherent part of the diffusion process that cannot be neglected on intuitive grounds. This investigation is an inquiry into the influence of antisymmetric boundary conditions on the magnitude of the hygrothermal stresses in a plate made of T300/5208 epoxy material, commonly used in graphite fiber-reinforced composites. Both moisture and temperature boundary conditions are considered. Because of the nonlinear character of the coupled equations, a finite-difference scheme is adopted. Numerical results involving time-dependent moisture, temperature, and stress distributions in the plate are displayed graphically; they show that the stresses derived from the coupled theory differ appreciably from the uncoupled results, both qualitatively and quantitatively. The hygrothermal stresses with coupling taken into account acquire an oscillatory character when the temperature on the plate is raised suddenly; this factor could contribute to material damage. In addition, antisymmetric boundary conditions can either raise or lower the stress levels, depending on time and the transient nature of the applied temperature.

Geometrical Effects of Filament Twist on the Modulus and Strength of Graphite Fiber-Reinforced Composites

Geometrical Effects of Filament Twist on the Modulus and Strength of Graphite Fiber-Reinforced Composites