National Hypersonic Science Center for Materials and Structures.

摘要

Research performed under the National Hypersonic Science Center for Materials and Structures (NHSC-MS) aimed to advance the basic science needed to guide design of new high-temperature oxidation-resistant ceramic materials and to develop characterization and analysis tools that enable life prediction for fiber-reinforced composites with geometrically complex microstructures. Highlights of the research are as follows: The roles of transition element dopants in affecting oxidation resistance of ZrB2 ultra-high temperature ceramics, through the effects of the dopants on sintering and/or stability of the oxidation products (ZrO2, B-O glasses, and B-Si-O glasses), were elucidated through experiments and atomistic calculations. Structure, oxidation behavior, and stability of HfSiCNO ceramics were determined by experiment and atomistic calculations. The potential for beneficial oxidation reactions to form 'self- healing' layers containing compounds that are resistant to water vapor erosion was explored. Two new experimental methods were developed for characterizing fiber architectures in ceramic matrix composites and observing/measuring the evolution of damage under load at high temperatures, above 1500 deg C. One method uses digital surface image correlation and the other uses synchrotron x- ray micro tomography, which is capable of micron-scale resolution in 3- dimensional images. Under the umbrella of a virtual test system, methods were developed for: (i) analyzing 3-dimensional images of microstructures of fiber reinforced composites to create statistical characterization of the microstructure, (ii) formulation of a probabilistic generator for creating virtual specimens that replicate the measured statistics, and (iii) creation of a computational model for a virtual specimen that allows representation of discrete damage events.