Lattices materials range 

from open and closed cell foams across a wide range of length scale to micro-architectured, 

multi-phase solids that are manufactured by additive manufacture.

 Size effects are important too: 

lattices with struts of small diameter are subjected to high gradients of strain in bending and are consequently have a higher material strength than large scale lattices. The focus of this talk is on the effect of filling of a 2D hexagonal lattice or a 3D Kelvin lattice upon their macroscopic stress versus strain responses. To first order, the presence of an incompressible in-fill reduces the degrees of freedom by which the lattice can deform. Consequently, the deformation mode of the lattice can switch from bending-dominated to stretching dominated 

1. with a large concomitant elevation 

2. to stiffness and strength. 

3. Instabilities can develop, 

4. and cavitation plays a major role.

Norman Fleck is Professor of Mechanics of Materials (since 1997), and Director of the Cambridge Centre for Micromechanics (1990) at Cambridge University Engineering Department. He was Head of the Mechanics, Materials and Design Division of the Cambridge University Engineering Department 1996-2008. He conducted a PhD in metal fatigue at Cambridge University (1980-1984), followed by post-doctoral research at Cambridge University and at Harvard University, USA with 

• John Hutchinson and Bernard Budiansky. 

• He is a leader in the experimental and theoretical mechanics 

• of engineering materials.  

• He has been elected to several learned Societies (Fellow of the London Royal Society, Fellow of the Royal Academy of Engineering, US National Academy of Engineering, European Mechanics Society, Academia Europea and the European Academy of Sciences). He is the currently President of IUTAM.

Speaker: Norman A. Fleck, Cambridge University, UK