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Content archived on 2024-04-16

CHEMICAL VAPOUR INFILTRATION IN NEW DESIGNED COMPOSITES WITH REDUCED INFILTRATION TIMES BY PRESSURE GRADIENTS AND MONITORED BY INSITU ANALYSIS WITH SPECTROSCOPIC MEANS

Objective


Carbon fibre reinforced silicon carbide ceramics with newly designed fibre architectures have been engineered, manufactured and tested. The infiltration process itself and the mechanical properties of the fibre reinforced composite materials were modelled. Both models were validated by the results of laboratory infiltration experiments and by mechanical tests, respectively. Because of the reduction in infiltration time, pressure gradient or forced flow chemical vapour infiltration (FCVI) has been shown to have a high economic potential. Analysing this process by in situ Fourier transform infrared spectrometry (FTIR), many chemical species in the hot zone could be identified and indicated process interferences at an early stage of the silicon carbide deposition process. The carbon fibre reinforced silicon carbide composites were designed and prepared with respect to their foreseen applications: damage tolerant composite materials and fibre reinforced bandage material for seal rings. They were tested under near service life conditions.
Chemical vapour infiltration (CVI) is a superior technique for densifying newly designed 2d and 3d carbon fibre preforms in order to get a composite with properties such as shear strength and damage tolerance which are unattainable with conventional 2d laminates.

The main disadvantages of CVI (long process times and process instabilities) have to be overcome, especially if complex shaped components of these preforms have to be infiltrated. This will be in this programme by applying pressure gradients to direct the gas flow and to install automatic pressure gradient control. Furthermore, process instabilities e.g. gas phase nucleation will be detected by in-situ IR-spectroscopic analysis in a very early process stage. These CVI process improvements will be an important prerequisite for the production of the newly designed 2d and 3d carbon fibre composites. Their mechanical and physical properties will be gained by testing and by finite element calculations.

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Coordinator

Messerschmitt-Bölkow-Blohm GmbH (MBB)
EU contribution
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Address

8000 MÜNCHEN
Germany

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Participants (5)