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MEAM Seminar: “From Mollusk Shells to Dense Architectured Materials to Granular Crystals: How Building Blocks and Weak Interfaces Create High Mechanical Performance”
April 5 at 10:00 AM - 11:30 AM
Regular building blocks of controlled shape and size can be assembled to create fully dense “architectured” materials and structures. When the building blocks are very stiff and when they interact through much softer materials or even only by frictional contact, the blocks can slide, rotate, separate or interlock collectively, providing a wealth of tunable mechanisms, precise structural properties and functionalities. In this talk I will illustrate this design strategy with three examples: First, I will show how the brick-and-mortar architecture of nacre from mollusk shell exploits near-perfect structural periodicity and geometric hardening to promote large deformations and toughness, which are key features we recently translated into tough, impact resistant bioinspired glasses. In the next example geometric hardening is pushed to the extreme to create geometrical interlocking. Tetrahedral or octahedral blocks are assembled into “topologically interlocked” panels, which can turn brittle ceramics into ductile, tough and damage tolerant 2D panels purely from the interplay of block geometry, interlocking and frictional sliding. Finally, my third example will show how this design principle can be extended to three-dimensional granular crystals. Here we assembled millimeter-scale 3D printed grains of specific geometries into fully dense crystals, which we found are 10 times stronger than traditional granular materials. These granular crystals display a rich set of mechanisms: Nonlinear deformations, crystal plasticity reminiscent of atomistic mechanisms, shear-induced dilatancy, micro-buckling. Once fully understood and harnessed, we envision that these mechanisms will lead to engineering materials with unusual and attractive combinations of mechanical performances.
Professor, Paul M. Raddy Department of Mechanical Engineering, University of Colorado at Boulder
Francois Barthelat is Professor of Mechanical Engineering at the University of Colorado Boulder. He obtained his PhD from Northwestern University in 2006, and was a Professor in Mechanical Engineering at McGill University (Montreal, Canada) from 2006 to 2019. Francois Barthelat founded the Laboratory for Advanced Materials and Bioinspiration to explore key structures and mechanisms in natural materials, and to develop new bioinspired, high-performance materials. Dr. Barthelat and his students have discovered new deformation and fracture mechanisms in bone, in mollusk shells and in fish scales. They have also pioneered new bioinspired materials and systems which they are now implementing in engineering applications. He is the recipient of the Hetényi Award for best research paper in Experimental Mechanics, of a Discovery Accelerator Supplement from NSERC, and of a Department of National Defence /NSERC Discovery Grant Supplement. Barthelat serves on the editorial board of Scientific Reports, Bioinspiration and Biomimetics, Mechanics of Materials and the Journal of the Mechanical Behavior of Biomedical Materials.