Effect of the Matrix and Matrix Bonding on the Creep Behavior of a Unidirectional Carbon–Carbon Composite

Sines, George; Zheng, Yang; Vickers, Brian D.

doi:10.1111/j.1151-2916.1989.tb05953.x

Cited by 16 publications

(3 citation statements)

References 3 publications

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“…The carbon matrix significantly enhances the carbon fibers' resistance to creep deformation owing to the ability of the matrix to distribute loads more evenly and to impose a plastic flow-inhibiting, triaxial stress state in the fibers [243]. The thermally activated process for creep is controlled by vacancy formation and motion.…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Science of composite materials

Chung

2003

Engineering Materials and Processes

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Composite materials are those containing more than one phase such that the different phases are artificially blended together. They are not multiphase materials in which the different phases are formed naturally by reactions, phase transformations or other phenomena.A composite material typically consists of one or more fillers (fibrous or particulate) in a certain matrix. A carbon fiber composite is one in which at least one of the fJ.llers is composed of carbon fibers, either short or continuous, unidirectional or multidirectional, woven or non-woven. The matrix is usually a polymer, a metal, a carbon, a ceramic or a combination of different materials. Except for sandwich composites, the matrix is three-dimensionally continuous, whereas the fJ.ller can be three-dimensionally discontinuous or continuous. Carbon fiber fJ.llers are usually three-dimensionally discontinuous, unless the fibers are three-dimensionally interconnected by weaving or by the use of a binder such as carbon.The high strength and modulus of carbon fibers make them useful as a reinforcement for polymers, metals, carbons and ceramics, even though they are brittle. Effective reinforcement requires good bonding between the fibers and the matrix, especially for short fibers. For an ideally unidirectional composite (i.e., one containing continuous fibers all in the same direction) containing fibers of much higher modulus than that of the matrix, the longitudinal tensile strength is quite independent of the fiber-matrix bonding, but the transverse tensile strength and the flexural strength (for bending in longitudinal or transverse directions) increase with increasing fiber-matrix bonding. On the other hand, excessive fiber-matrix bonding can cause a composite with a brittle matrix (e.g., carbon and ceramics) to become more brittle, as the strong fiber-matrix bonding causes cracks to propagate in a straight line in a direction perpendicular to the fiber-matrix interface, without being deflected to propagate along this interface. In the case of a composite with a ductile matrix (e.g., metals and polymers), a crack initiating in the brittle fiber tends to be blunted when it reaches the ductile matrix, even when the fiber-matrix bonding is strong. Therefore, an optimum degree of fiber-matrix bonding (i.e., not too strong and not too weak) is needed for brittle-matrix composites, whereas a high degree of fiber-matrix bonding is preferred for ductile-matrix composites.The mechanisms of fiber-matrix bonding include chemical bonding, interdiffusion, van der Waals bonding and mechanical interlocking. Chemical

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Section: Mechanical Propertiesmentioning

confidence: 99%

Science of composite materials

Chung

2003

Engineering Materials and Processes

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“…In early works, only creep of ceramics in general is discussed 12,13 . Later, various investigations have been made on carbon fibres and carbon–carbon composites, the method of performing creep with carbon fibres has been enhanced 14 and creep parameters have been evaluated 15 . Activation energies have been measured for different types of fibres (pitch‐based in comparison to PAN‐based) 16 …”

Section: Introductionmentioning

confidence: 99%

Structural change of carbon‐fibres at high temperatures under load

Rennhofer

Loidl

Brandstetter

et al. 2006

Fatigue Fract Eng Mat Struct

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A B S T R A C T Creep tests were performed with carbon fibre-bundles (Toho Tenax) in a temperature range from 1500 to 1800 • C. The fibre-bundles were electrically heated in vacuum (pressure 10 −4 mbar) and tensile load was applied in a hydraulic testing machine. The creep parameters were obtained from varying temperature and loading conditions. Accompanying structural investigations were performed with X-rays (SAXS and WAXD). An increasing orientation of the graphene planes along the fibre (and thus the loading axis) could be observed with increasing temperature and load. No structural change and no creep, however, was observed for carbon fibres stabilized by an appropriate heat treatment. = interlayer-distance of graphene planes I(q, χ) = intensity-distribution L p = pore length q = absolute value of the scattering vector Q = activation energy for creep R g = radius of gyration R = gas constant, equals 8.314 J mol −1 K −1 T = temperaturė ε = strain rate θ = 1 2 of the scattering angle λ = X-ray wavelength σ = stress applied to the fibres χ = azimuthal angle I N T R O D U C T I O NCarbon fibres exhibit outstanding mechanical properties (high elastic modulus, high tensile strength and low weight), which are maintained up to high temperatures. Thus, these fibres are especially suited as reinforcing elements in composites for high-performance applications. 1 Carbon fibres are built up by hexagonal graphene layers forming small coherent units (crystallites separated by pores). 2 The crystallites with a size of some nanometers are preferentially oriented along the fibre axis, the degree of orientation being the most important parame-ter for the Young's modulus of the fibres. To determine this orientation and to gain information on the structure at the nanometer level, wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) are one of the most important techniques. 3-6 The degree of orientation and the interlayer distance can be determined from the distribution and the position of the 002-reflection in WAXD, 7,8 whereas SAXS can be used to quantify the mean orientation and the size of the pores. 9,10 For polyacrylonitrile-(PAN) based fibres, the most important parameter to control the structure is the final heat treatment. This heat treatment has been intensively discussed in the literature. 3,7,10,11 A high-temperature treatment changes the structure of the carbon fibres: the higher

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“…Usually, the carbon/carbon composites have laminated structures. Because the laminated composites have no through-the-thickness reinforcing fibres, they are apt to be broken by delamination [4][5][6][7][8] . The fabrication of composites using needle-punched preforms has made it possible to overcome interlaminar failure problems 9 .…”

Section: Introductionmentioning

confidence: 99%

Effect of Punching Density on the Mechanical and Thermal Properties of Needle-punched Nonwoven Carbon/Phenolic Composites

Kang

Jung

Park

et al. 2002

Polymers and Polymer Composites

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The effects of changes in the fibre orientation on the mechanical properties of nonwoven composites were investigated through 3-point bending, short beam shear and tensile tests. Oxidized polyacrylonitrile(PAN) carded webs were needle-punched, and then carbonized to fabricate carbon composites with phenolic resin. The interlaminar shear, tensile and flexural strengths increased with increasing punching density. However, the rate of increase reduced and interlaminar shear and tensile strengths decreased with excessive punching density. The erosion rate and the insulation index were calculated by means of a torch test. The ablation resistance increased with increasing punching density, but no significant increase in the erosion rate with increasing punching density above 477 penetrations per square centimetre was found. The thermal conductivity of needle-punched nonwoven carbon/phenolic composites increased with increasing punching density.

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Effect of the Matrix and Matrix Bonding on the Creep Behavior of a Unidirectional Carbon–Carbon Composite

Cited by 16 publications

References 3 publications

Science of composite materials

Science of composite materials

Structural change of carbon‐fibres at high temperatures under load

Effect of Punching Density on the Mechanical and Thermal Properties of Needle-punched Nonwoven Carbon/Phenolic Composites

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