Effect of zigzag damage extension mechanism on fracture toughness of cross-ply laminated carbon/carbon composites

摘要

The fracture behavior and damage mechanisms of a cross-ply-laminated carbon/carbon (C/C) composite was investigated using compact tension (CT) and double-edge-notched (DEN) geometry. The C/C composite exhibited an interesting 'zigzag cracking' during growth of the damage in the 0degrees plies. At the same time, a straight crack extension was formed in the 90degrees plies. This zigzag crack proceeded in the following order: at first, vertical splits formed, then micro-cracks between the splits, and finally a connecting unstable crack formed. A stable/unstable regime of zigzag cracking was repeated for several cycles until the final failure, An R-curve was determined, taking this cracking extension into account. The R-curve demonstrated that the high-fracture toughness of the cross-ply laminated C/C composites could be attributed to the zigzag cracking characteristics. Then, the DEN results were compared with the R-curve behavior. This comparison showed that the DEN occurred at the initial value of the R-curve obtained when the micro-crack growth length was regarded as the crack tip. [References: 18]