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“design intent” principles considers the functional role of materials systems at the conceptual design stage, including how they carry thermal and aerodynamic loads in a hypersonic application. Craig Przybyla (AFRL) discussed development and use of automated techniques to quantify microstructure– property relationships in continuousfiber reinforced composites. In particular, understanding response variability in composites requires quantifying the underlying variability of microstructure. Codes are required that can import, interpret, and represent stochastic microstructure data. However, imaging, segmentation, and material structure quantification traditionally are labor- and time-intensive processes, particularly with 3-D tomography or serial-sectioned materials microstructure data. Software tools were demonstrated that automate image registration, segmentation, and feature extraction for large, high-resolution 3-D material datasets obtained via robotic serial sectioning and optical microscopy for SiC–SiC composites. Moreover, researchers used these tools to implement DREAM.3D software that consolidates custom data analysis tools for construction of customized data analysis workflows. The DREAM.3D package is freely available to the research community (dream3d.bluequartz.net). Researchers can use this software to statistically quantify and visualize in a virtual environment 3-D microstructure data. Researchers then can use these data to generate microstructure models for simulation or to link back to experimental response characterization to quantify stochastic microstructure–property relationships. The automated tools and approaches described herein support the broader goals of MGI that seek to optimize materials development through application of Integrated Computational Materials Engineering (ICME). ICME is “the integration of materials information, represented in computational tools, with engineering product performance analysis and manufacturing process simulation.”5 To this end, Przybyla discussed how physics-based microstructure-sensitive Figure 1. Evolution of computation and modeling efforts. models are being developed to predict response variability based on inherent microstructure variability in the material, quantified using the automated approaches described. Specifically, he discussed a physics-based approach to model oxidation behavior of SiC/SiC composites. When these physics-based modeling tools are coupled with automated microstructure quantification tools, the vision of ICME is closer to reality for continuous-fiber-reinforced composites, such as ceramic-matrix composites in development for current extreme environment aerospace applications. Thermal protection materials Modeling of the behavior of thermal protection systems (TPS) was discussed by Sylvia Johnson (NASA). Considerable work on this topic is underway at the NASA-Ames Research Center (Moffett Field, Calif.). Researchers have developed codes to predict aerothermal environments that allow vehicle designers to establish TPS material and system requirements for hypersonic flight and re-entry vehicles. Johnson noted that the type of analysis required depends on the system and the information needed. She outlined a minimum set of inputs required, including • Complete set of accurate thermal and mechanical properties for all materials in the model; • Thermal and mechanical environmental and boundary conditions appropriate for the model; and • Use of physics- and chemistrybased models (rather than correlations) Credit: ASDR&E with parameters that can be obtained from experiments. Johnson says multiscale models can account for physics and chemistry across a spectrum of length and time scales. NASA research on TPS materials focuses on the need to account for processes, such as pyrolysis, ablation, and location (e.g., leading edges versus windward aeroshell), as well as associated changes in the material, shape, and aerodynamic response. She noted that NASA considers the models to be in a relatively advanced stage. Brian Sullivan (Materials Research & Design Inc.) discussed TPS panels in hypersonic vehicles. In the past, these panels were intended solely to protect the internal structure from the heat of hypersonic flight. He pointed out that these TPS were considered “parasitic mass,” because their function was entirely thermal and not load bearing. Recently, however, load-bearing TPS have become more prevalent, incorporating features that provide a more integrated function for the vehicle. Sullivan discussed examples for using ICME to design C/SiC and SiC/SiC composites for this and other applications and how features, such as foreign object damage resistance, can be modeled via failure analysis to guide materials fabrication methods. American Ceramic Society Bulletin, Vol. 95, No. 3 | www.ceramics.org 37


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