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Laser based coating of carbon fibres for manufacturing CMC


Fuentes, M.; Martinez-Esnaola, J.M. ; Centro de Estudios e Investigaciones Tecnicas de Guipuzcoa -CEIT-, San Sebastian:
First International Conference on Ceramic and Metal Matrix Composites 1996. Proceedings
Uetikon-Zürich: Trans Tech Publications, 1997 (Key engineering materials 127/131)
ISBN: 0-87849-753-6
International Conference on Ceramic and Metal Matrix Composites (CMMC) <1, 1996, San Sebastian>
Conference Paper
Fraunhofer IWS ()
CVD; Faserbeschichtung; Verbundwerkstoff; Faser; Schicht

In order to promote high temperature applications of C/C(SiC) composites, complex oxidation protection systems have been established, including deposition of layers on fibre bundles and preforms, partially converting the matrix by liquid silicon infiltration, and the final encapsulation of the composite material by SiC/MoSi2 layers. A laser driven CVD method (LCVD) has been introduced for coating fibres. Based on an industrial 5 kW cw-CO2 laser an atmospheric pressure LCVD process has been established which performs a continuous high rate coating of rovings. The influence of laser deposition on mechanical properties and structure of the coated fibres has been checked by tensile (bundle) testing, SEM/EDX, and Raman spectroscopy. Using C2H4 and CH4 as precursors, layers of highly ordered pyrolytical carbon have been deposited with a rate of 1.4 mu m/s, enhancing tensile strength, elastic modulus and Weibull modulus of the fibres. Deposition onto fibre bundles of 2D-fabrics and on preforms is performed in industrial hot wall CVD batch reactors with monolayer and double layer configuration: pyro-C, SiC, BN. The hot wall CVD method decreases tensile strength and elastic modulus of the fibres. For screening chemical stability, the selected coating systems have been tested by liquid silicon infiltration. Highest durability is exhibited by the double layer systems. The monolayer systems show low stability with the exception of BN which is not wettable.