Development of nondestructive evaluation methods and prediction of effects of flaws on the fracture behavior of structural ceramics

摘要

In the NDE area, specimens with different cloth lay-up orientations were examined by a 3-D X-ray microtomography device and image processing to measure and map in-plane fiber orientations. Results show detection sensitivity to better than plus or minus 3(degrees). We establish detection of 3-D braid/weave fiber orientation and spacing. Another NDE method, multinuclear ((sup 13)C,(sup 29)Si, and (sup 11B) NMR spectroscopy, is being developed to determine the chemical state of the fiber surface and its potential impact on fiber pullout. We have conducted initial studies to investigate sensitivity to bulk composition of the matrix materials (a,b, amorphous phase, silica, and oxynitride concentration). The first (sup 29)Si NMR experiments focused on methods to enhance the signal from the surface by selectively reducing surface relaxation. Additionally, we have determined that there is sufficient sensitivity of (sup 11)B NMR for monitoring fiber coatings.