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Figure 4 The MEDE CRA will develop and apply computational materials design concepts for boron carbide and S-glass/epoxy composites. Other materials included in the study are magnesium-based alloys and ultra-high-molecular-weight polyethylene. for easy funding changes to enhance or start new work. Also, the CA approach allows for the rapid transition of new knowledge, techniques, or breakthroughs to ARL inhouse programs. Q. One of ARL’s stated goals is to “change the way scientists look at designing advanced materials.” How? A. The “materials by design” approach has been getting more and more traction over the past 10 years or so, and the publication of the National Academies report in integrated computational systems engineering2 reemphasized the multiscale aspects of designing materials, especially in an engineering context. As computational capability has increased and characterization of materials down to the atomic structure scale—both postmortem and during actual tests—has evolved, the importance of the microstructure and the atomic structure has increased. Better understanding of the contributions to inelastic deformation, damage evolution and catastrophic failure across the scales will allow for materials design at the atomic structure and nanoscale microstructure of materials. Basically, the MEDE constorium wants to identify the critical mechanisms, understand them, and control them. Q. There has been an increased focus on advanced manufacturing in recent years. Does this program address advanced manufacturing issues and challenges? A. In the MEDE CRA there are three industrial components, and (Credit: ARL.) the basics of their involvement will evolve: ceramics at Rutgers; polymers and composites at the University of Delaware; and metals at Johns Hopkins. As new synthesis and processing methods are developed in MEDE, as well as compositional recommendations, this information will be passed on to the consortium members for the more manufacturing-intense work. Q. Regarding MEDE, what are extreme dynamic environments and how do they affect the soldier? A. Strain rates to 106 per second and stress to 50 GPa: These are generic dynamic environments for very severe impact events. Basic research in these environments will help us understand the underpinning physics that will be passed to our inhouse program for use in our more controlled, secure environment. This is called a “Canonical Model Approach,” which is defined as a simplified description of a system or process, accepted as being accurate and authoritative, developed to assist calculations and predictions, to connect to the ARL internal programs. Q. Four materials will be investigated: boron carbide, magnesium, ultra-highmolecular weight polyethylene, and glass/ epoxy composite. Why these four materials? A. These are the materials that the Johns Hopkins CRA selected as the representative of the four required classes of materials in the program announcement. All four meet the criteria for enhancing the possibility of producing very lightweight protection material systems. Magnesium is the lightest structural metal; B4C is the lightest armor ceramic; UHMWPE has the highest apparent probability of achieving significantly increased mechanical strength and the same for S-glass/epoxy composites (Figure 4). Q. There is already a lot of research behind these materials. How does computational materials design ideas apply to known materials, for example, boron carbide? What issues are driving the materials development? A. Basically, we are extending the approach beyond the simple property figures of merit to the underpinning or controlling mechanisms down to the lowest scale. These mechanisms control the properties, especially in extreme dynamic events. There is a significant shortfall in our understanding of boron carbide in all of the thrust areas (Table 1), especially in the modeling and simulation/scale bridging areas. In particular, we know very little about the atomic origins of amorphization, inelastic deformation, etc., at the atomic scale. The MEDE CRA selected boron carbide as the model ceramic because they believe the material has unrealized potential for dramatic improvements in ballistic performance for soldier and vehicular armor at very low weight. They seek to understand and control the dynamic failure processes in this armor ceramic material and improve its dynamic performance by eliminating weak links at the atomic and microstructural levels through multiscale modeling, advanced powder synthesis, control of polytypes, and microstructural improvements. Q. At the decision point in five years, what does success look like for MEDE? A. The big ones, obviously, for the first five years are the two- and five- year goals. What we hope to accomplish after the first two years is an improved physics-based algorithm that we can put into a continuum code that American Ceramic Society Bulletin, Vol. 92, No. 2 | www.ceramics.org 29


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