Computation and modeling applied to ceramic materials

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Computation and modeling applied to ceramic materials By Steve W. Freiman, Lynnette D. Madsen, and William Hong Introduction Computation and modeling are increasingly augmenting— and sometimes even replacing—experimentation for understanding and predicting properties and behavior of materials. A oneday workshop held in conjunction with the 2015 annual meeting of the Interagency Coordinating Committee for Ceramic Research and Development (ICCCRD) focused on the topic of computation and modeling as applied to ceramic materials. ICCCRD comprises representatives from government agencies that have programs with an interest in, or focused on, ceramics.1 Individuals attending the workshop represented the National Science Foundation (NSF), Defense Advanced Research Projects Agency (DARPA), Department of Energy (DOE), Office of the Assistant Secretary of Defense for Research and Engineering (ASDR&E), National Aeronautics and Space Administration (NASA), Office of Naval Research (ONR), Air Force Research Laboratory (AFRL), National Institute of Standards and Technology (NIST), Naval Research Laboratory (NRL), and Naval Surface Warfare Center (NSWC). Speakers from academia, industry, and government national laboratories also participated. Workshop topics vary from year-to-year; summaries of some of the previous workshops were published on the topics of materials databases,2 scarce materials,3 and ceramic education.4 Ceramics, defined herein as any inorganic nonmetal (i.e., oxides, nitrides, carbides, and borides as well as glasses, single crystals, and carbon), are unique with respect to computation and modeling in terms of the sensitivity of their properties to starting materials—e.g., chemical composition, particle size, impurities, and processing conditions— under which they are made. Important characteristics, such as fracture behavior as well as electrical and optical properties, vary with small changes in composition and microstructure. Consequently, the same compound, e.g., silicon carbide (SiC) or aluminum oxide (Al2O3), manufactured by two organizations almost certainly will have different properties. In addition, knowledge of time and temperature dependences of such properties mostly is lacking. Modeling and simulation of these materials need to account for low-ductility failure modes, variability in fabrication processing and manufacturing, and effects of interfaces, e.g., grain boundaries. The 2015 workshop included a broad array of computation and modeling topics, including ceramic-matrix composites, thermal protection systems, first-principles calculations of material properties, and methodology for predicting mechanical reliability of materials. The diversity of these topics makes it difficult to give more than a brief flavor of the salient points. This article touches on issues mentioned in presentations and in recent publications and attempts to summarize key needs for future progress in computation and modeling. Workshop summary Lewis Sloter (ASDR&E) opened the workshop with a historical perspective conveyed in reports on the use of computation tools for more rapid insertion of new materials into manufactured products (Figure 1). He pointed out various activities that led up to the Materials Genome Initiative (MGI), in which computation and modeling play a major role. Ceramic-matrix composites Because of broad interest in fiber-reinforced ceramic composites as materials for a myriad of high-performance applications—e.g., thermal protection coatings, rocket nozzles, and gas turbine engines—researchers have focused significant attention on modeling properties and behavior of these complex materials. Jesse Margiotta (speaking on behalf of DARPA) discussed ways of incorporating computation and modeling of C/C and C/SiC composites for hypersonic vehicle structure applications. DARPA’s Materials Development for Platforms (MDP) program focuses on such an application. Margiotta noted that extreme environments challenge materials and design, and current performance is limited by availability of fully characterized, robust materials. MDP’s goal is to better align material and platform (application) development cycles to expand design options for both, using toolsets to guide materials development and predict fabrication needs in an accelerated time scale. Use of 36 www.ceramics.org | American Ceramic Society Bulletin, Vol. 95, No. 3


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