Bioinspired micro-composite structure
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H. Kahn and A.H. Heuer Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106 (Received 4 May 2006; accepted 13 September 2006)
This paper presents the design, fabrication, and mechanical testing of a bioinspired composite structure with characteristic dimensions on the order of tens of microns. The microarchitecture, designed and fabricated using microelectromechanical systems (MEMS) technology, involves two distinct length scales and represents the first attempt at mimicking the crossed-lamellar microstructure of molluscan shells such as the giant Queen conch, Strombus gigas, which contains features with dimensions spanning five distinct length scales. The displacement control capabilities of a nanoindenter enabled the observation of the graceful failure of the micro-composite under three point bending and, in turn, the measurement of its post-peak load–displacement response and work of fracture. I. INTRODUCTION
Studies performed on natural brittle materials suggest a pervasive theme, namely that nature makes structures, not materials, and that these structures are often laminated. The structures created by organisms, although made from rather mundane materials, show impressive properties, which furthermore are very well suited for the intended function (structure/function/performance correlations have been assumed due to natural selection). The diversity of microstructure in molluscan shells testifies to the flexibility of this approach. It would be desirable if materials scientists developed techniques to produce structures, as opposed to materials, and undertook such developments in collaboration with mechanical designers. Study and careful analysis of naturally occurring composites—an aspect of the so-called biomimetic or bioinspired approach—can provide much insight for the design of new, improved materials, particularly composites composed of a large volume fraction of a brittle constituent. Laminated structures composed of mostly brittle constituents offer promise in a wide range of applications, including hot section components in aircraft engines, pavement material for airfields and roads, and electronic packaging. Exploration of the mechanical behavior of a diverse ar-
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Address all correspondence to this author. Present address: Department of Civil Engineering, University of Minnesota, Minneapolis, Minnesota 55455. e-mail: [email protected] DOI: 10.1557/JMR.2007.0016 124
http://journals.cambridge.org
J. Mater. Res., Vol. 22, No. 1, Jan 2007 Downloaded: 14 Mar 2015
ray of microstructural designs through fabrication and mechanical testing is economically prohibitive. Therefore, the development of bioinspired structural designs will undoubtedly rely on multiscale computational tools whose predictions will be assessed through limited numbers of carefully designed experiments. Microelectromechanical systems (MEMS) technology offers promise for prototyping structural designs of laminated composites and can provide data to assess the predictive capabilit
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