Material Design Paradigms for Optimal Functional Gradient Armors

Report No. ARL-RP-92
Authors: David S. Kleponis, Audrey L. Mihalcin, and Gordon L. Filbey, Jr.
Date/Pages: April 2005; 12 pages
Abstract: Computational modeling is used to derive desired through-thickness gradients in material strength for optimal performance of functional gradient materials as armors. The basic thesis is that one does not know a priori what variation in a given material property, such as hardness or yield strength, is necessarily the best choice for optimal ballistic performance in a tailored armor material. Choices for how such a property should be distributed may exist, but attempting to fabricate and experimentally test every possible choice is not the most efficient way to proceed to answers. A common fabrication procedure for such materials is to build them in layers, which allows one to change materials somewhat from layer to layer. In order to gain confidence in designing the thickness of various layers and the desired material properties, we first modeled computationally the ballistic performance of layered steel constructs with the Eulerian wave code CTH. The layered steel calculations revealed surprising trends as related to the distribution of strength properties among the various layers, as well as for the limit-layer thickness. Conventional wisdom of ?hard-to-soft? is not necessarily the optimal answer.
Distribution: Approved for public release
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Last Update / Reviewed: April 1, 2005