Compressional behaviour of carbon fibres

Melanitis, N.; Galiotis, Costas

doi:10.1007/bf00580133

Cited by 71 publications

(27 citation statements)

References 17 publications

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“…The proportion and the distribution of the carbon and SiC phases differ in the fibres and, yet, a global classification is possible. Note that a direct proportionality between S 3 and E has been reported in the literature but these results were based on a narrower exploration of Young's Modulus, limited to aramid [447,467,491], polyethylene [492] or carbon [453] fibres. Deviations from the linear trend in Fig.…”

Section: Young's Modulus and ''Raman Microextensometry''mentioning

confidence: 93%

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Raman Spectroscopy of nanomaterials: How spectra relate to disorder, particle size and mechanical properties

Gouadec

Colomban

2007

Progress in Crystal Growth and Characterization of Materials

903

714

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The purpose of this review is to provide non-specialists with a basic understanding of the information micro-Raman Spectroscopy (mRS) may yield when this characterization tool is applied to nanomaterials, a generic term for describing nano-sized crystals and bulk homogeneous materials with a structural disorder at the nanoscale e typically nanoceramics, nanocomposites, glassy materials and relaxor ferroelectrics. The selected materials include advanced and ancient ceramics, semiconductors and polymers developed in the form of dots, wires, films, fibres or composites for applications in the energy, electronic and aeronauticseaerospace industries. The text is divided into five sections:

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Section: Young's Modulus and ''Raman Microextensometry''mentioning

confidence: 93%

“…At the macroscopic scale, fibres present the same tendency as their bonds to strengthen in compression and soften in tension [453]. Hooke's law being nothing but the macroscopic manif estation of bond stiffness, one may indeed expect to find a relationship linking E to k b (introduced in Eq.…”

Section: Young's Modulus and ''Raman Microextensometry''mentioning

confidence: 98%

Raman Spectroscopy of nanomaterials: How spectra relate to disorder, particle size and mechanical properties

Gouadec

Colomban

2007

Progress in Crystal Growth and Characterization of Materials

903

714

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“…Tarantili et al found a/b typically equal to 25 for the "symmetric" C-C stretching mode of polyethylene fibers [77] but Melanitis et al found a/b∼5 (only !) in "PAN-based" carbon fibers [78] . However, SiC fibers being much more isotropic than carbon fibers (strong covalent bonds in all directions), a greater reversibility is expected when passing from tensile to compressive stress.…”

Section: Raman Spectra Relationship With Young's Modulus and The Micrmentioning

confidence: 99%

Non-destructive mechanical characterization of SiC fibers by Raman spectroscopy

Gouadec

Colomban

2001

Journal of the European Ceramic Society

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The paper provides a comprehensive study on Raman spectroscopy versatility as a fast and non destructive tool for the prediction of the mechanical properties of SiC fibers derived from a polymeric precursor (NLM™, Hi™, Hi-S™, SA™ and Sylramic™ grades) or produced by CVD (SCS-6™ fiber), including in situ analysis in CMCs or MMCs. We show how the results of very simple spectra fitting are correlated with Young's modulus, tensile strength and microhardness. The reason why such a correlation exists, the common dependency of Raman signal and mechanical behavior to the micro/nanostructure of ceramics, is discussed. Keywords :SiC-fibers / Raman spectroscopy / Mechanical properties / Microstructure / Carbon ∂ Author to whom correspondence should be addressed Fax : 33 (0) 1 49 78 13 18 e-mail : colomban@glvt-cnrs.fr IntroductionThe reinforcement of ceramic materials by long ceramic fibers leads to low density and refractory materials, of high damage tolerance, that should be appropriate for metal alloys substitution in advanced engines (turbines) and waste treatment energy plants [1] . Ceramic fibers can also be incorporated directly in metal matrices to increase their high temperature mechanical properties [1] .SiC fibers, which are among the most stable fibers, have always been produced by the 3D reticulation of a polymeric precursor. This synthesis route leads to a high matter homogeneity and very smooth surfaces, the lack of defects explaining tensile strengths σ r as high as 3 GPa. SiC fibers have been widely studied, especially their aging [2][3][4][5][6][7] which evidenced that densification is linked to compositional changes (for instance the loss of some residual hydrogen [8] ). A peculiarity of ceramics issued from polymeric precursors is no impurities are concentrated at the grains boundaries. Abnormal grain growth is very common in the lack of such usual diffusion regulators [9] and the know-how of SiC fibers manufacturers consists in postponing the onset of SiC crystallization and grain growth, since a high correlation is anticipated with mechanical degradation. A close relationship has been evidenced, for instance, between the micro-hardness and short-range ordering in sol-gel prepared nanocrystalline oxides [10] and some authors have already pointed out fibers overall mechanical ability is governed by their microstructure [5,7,11] .The purpose of this paper is to try correlating, to the best extent possible, the tensile strength (σ r ), the Young's modulus (E) and the micro-hardness (μH) of different SiC fibers, either to Raman spectra or to "Raman Extensometry" S coefficient (measuring the straininduced shifts of Raman bands). Unlike most experimental methods intended to measure directly σ r and E, Raman analysis does not require extracting fibers from the matrix, either by mechanical grinding/crushing [12] or by chemical attack [13] . Only the most resistant fibers are extracted in the former case while fibers surface might be altered in the latter. Besides, it will always be difficult to extract...

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“…To calibrate the strain dependence of Raman frequencies in compression, single filaments are bonded to the surface of an elastic polymer cantilever beam which is then flexed to compress the fibres [41]. By scanning along the fibre with the laser Raman microprobe plots of Raman frequency as a function of applied compressive strain are obtained [9]. A specially designed tensometer was used to stress the carbon fibre/epoxy samples along the fibre direction on the Raman microscope stage.…”

Section: Laser Raman Spectroscopy/mechanical Loadingmentioning

confidence: 99%

“…The latter is normally preferred for this application because it is highly selective and capable of probing areas in the region of 1-2 Itm. Previous work has shown that the Raman frequencies of all different grades of carbon [4][5][6] and aramid [1,7,8] fibres shift to lower values under tension and to higher values under compression [9,10] in a well defined and reversible fashion.…”

Section: Introductionmentioning

confidence: 99%

Interfacial Shear Stress Distribution in Model Composites Part 2: Fragmentation Studies on Carbon Fibre/Epoxy Systems

Melanitis

Galiotis

Tetlow

et al. 1992

Journal of Composite Materials

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The micromechanics of reinforcement of a model composite system consisting of a continuous high-modulus (HM) carbon fibre embedded in an epoxy resin have been investigated. The composite was subjected to incremental tensile loading up to full fibre fragmentation, while the strain in the fibre was monitored at each level of load using a laser Raman spectroscopic (LRS) technique. The average strain in the fibre increased linearly with applied matrix strain up to a value of 0.8 %, when the first fibre fracture occurred. After fracture, the strain in the fibre was found to build from the tips of the fibre breaks, reaching a maximum value in the middle of each fragment. The shape of the load transfer profiles at the locality of the fibre tips indicated that the stress transfer efficiency had been affected by the fracture process. The length of interfacial debonding at the point of fibre fracture was found to be driven by the strain energy of the fractured fragments.The interfacial shear stress (ISS) distributions at various levels of applied load along individual fragments, have been derived from the load transfer profiles using a balance of forces analysis. The shape of the ISS profiles confirmed that interfacial debonding initiated from the tips of the fibre breaks, whereas good fibre/matrix adhesion was retained around the mid-length of each fragment. By increasing the applied strain to 1.8%, the maximum ISS values also increased in spite of the presence of debonding at the fibre tips. An upper ISS limit of 42 MPa was calculated at this point. Further increases of the applied strain to 5% resulted in significant reductions in the values of the maximum ISS, as well as an increase, of the frictional slip towards the middle of each fragment. Finally, by employing the assumptions of the conventional fragmentation test, the calculated value of the nominal interfacial shear strength at the point of full fragmentation was lower by a factor of 2 than the value measured by the LRS method.

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Compressional behaviour of carbon fibres

Cited by 71 publications

References 17 publications

Raman Spectroscopy of nanomaterials: How spectra relate to disorder, particle size and mechanical properties

Raman Spectroscopy of nanomaterials: How spectra relate to disorder, particle size and mechanical properties

Non-destructive mechanical characterization of SiC fibers by Raman spectroscopy

Interfacial Shear Stress Distribution in Model Composites Part 2: Fragmentation Studies on Carbon Fibre/Epoxy Systems

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