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Volume 18, Issue 4, 2009
LETTER: REAL-TIME OBSERVATION OF DAMAGE NUCLEATION IN 3D BRAIDED CARBON/CARBON COMPOSITES
Jin Kan1, Liming Wei12 Songhe Meng1*, Chenghai Xu1
1 Centre for Composite Materials, Harbin Institute of Technology, Harbin 150080, China
2 Department of Mathematics, Heilongjiang Institute of Technology, Harbin 150050, China
* Author to whom correspondence should be addressed
Received 9 June 2009; accepted 19 October 2009
ABSTRACT
The micro mechanisms of flexure damage at the notch tip in a three-dimensionally braided carbon/carbon composite (3D–C/C) were investigated in real-time through a Scanning Electron Microscopy. It was found that the damage was nucleated in the fibre bundle/matrix interface around the notch tip. The different damage modes were found in different directions of the 3D–C/C. The x-directional flexural specimens seem to be insensitive to the pre-notch while the z-directional flexural specimens seem to be sensitive to the pre-notch. Fibre yarns acted as an obstacle to crack propagation and it was necessary to increase the load to propagate the crack through the adjacent fibre yarn. Comparing with the x-directional flexural specimens, the forces could be better transmitted in z-directional flexural specimens because the fibres of z-direction bundles can tightly adjoin to each other.
KEYWORDS:Carbon/carbon composites; Microstructure; Damage; Flexure fracture
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