Fracture Behavior of Carbon–Carbon Composites with Cross-Ply Lamination

Tensile fracture behavior of carbon–carbon composites with 0 /90 laminations were examined using double end-notched specimens. In the composites, the volume fractions of the 0 - and 90 -layers were systematically varied to observe the variation of fracture patterns as a function of the shear strength, which increased with the 0 -ply fraction, r. The fracture mode of the notched C–Cs was shown to transfer from Mode I to Mode II when r increased, with the transition occurring at r slightly higher than 0.5. When Mode II fracture occurred, complete notch insensitivity resulted. In contrast, when Mode I fracture was observed, slight notch sensitivity appeared. To evaluate fracture behavior more deeply, compact tension tests were performed. Resultant crack-resistance (R-) curves clearly explain the transition behavior from Mode I to Mode II. The R-curves also suggested that the slight notch sensitivity in the Mode I fracture was due to small scale splitting that appeared near the notch tips.