Abstract:

The structure of materials invariably defines their mechanical behavior. However, in most materials, specific mechanical properties are controlled by structure at widely differing length scales. Nowhere is this more apparent than with biological materials. Bone, dentin and nacre, for example, are sophisticated composites whose unique combination of mechanical properties derives from an architectural design that spans nanoscale to near-macroscopic dimensions; few engineering materials have such hierarchy of structure and properties. Unlike engineering composites where properties are invariably governed by the "rule of mixtures", the mechanical properties of many natural composite materials are generally far greater than their constituent phases. However, actually making such materials synthetically has proved to be extremely difficult, particularly in bulk form. Here we describe an approach, involving processing by ice-templating, to developing bulk ceramic-polymer nacre/bone-like structural materials with unprecedented strength/toughness properties. Indeed, we believe that these materials represent the highest toughness ceramics reported to date.

Biography:

Robert O. Ritchie is the H.T. & Jessie Chua Distinguished Professor of Engineering and Chairman of the Department of Materials Science and Engineering at the University of California, Berkeley; he is also Senior Faculty Scientist in the Lawrence Berkeley National Laboratory. He received B.A., M.A. and Ph.D. degrees in physics/materials science from Cambridge University (1966-1973) and the Sc.D. degree from there in 1990. Before joining the Berkeley faculty in 1981, he was the Goldsmith�s Junior Research

Fellow at Churchill College, Cambridge (1972-74), a Miller Research Fellow for Basic Research in Science in Berkeley (1974-76), and an Associated Professor of Mechanical Engineering at M.I.T. (1977-81). He is known for his research into the mechanics and micromechanisms of fracture and especially fatigue in a broad range of structural and biological materials, having published over 600 papers and edited 19 books in the technical literature. He is a member of the U.S. National Academy of Engineering and a Fellow of the Royal Academy of Engineering in the U.K. He is also a fellow of ASM, ASME, American Ceramics Society, MRS, TMS, the Institute of Physics, the Institute of Materials (London), and the International Congress on Fracture.