Notch sensitivity of a cross-ply laminate Carbon-Carbon composite(C/C) was investigated. Double edge notched (DEN) specimen havingvarious notch root radii was used to examine the notch sensitivity ofthe C/C. With increasing notch root radius, the fracture behavior ofthe C/C tended to become notch insensitive. The net fracture stressof the narrower width specimen was larger than that of un-notchedspecimens. However, the opposite tendency was observed in the widerwidth specimen, although the fracture stress of the un-notched C/Cwas independent of the specimen width. The point stress approach wasapplied to predict the fracture stress of the notched C/C as a firstorder approximation. The fracture of the C/C was successfullyexplained by setting the characteristic distance to 0.6 mm to 0.9 mm.The characteristic distance implies the existence of the process zonethat makes C/C notch insensitive. The fiber bundle hridging mechanismwas considered to explain the test result as the toughening mechanismoperating at the damaged area. The calculated result shows thereasonable fit with the experimental results.
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