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SUMMARY:Micromechanics of metallic and graphene (nano-)foams - Dr Patrick 
 Onck\, University of Groningen
DTSTART:20151113T140000Z
DTEND:20151113T150000Z
UID:TALK60495@talks.cam.ac.uk
CONTACT:Ms Helen Gardner
DESCRIPTION:In this talk I will focus on the failure properties of metalli
 c foams and the mechanics and charge-induced actuation of metal and graphe
 ne nanofoams. \nThe fracture strength of metal foams depends sensitively o
 n the properties of the constituent material as well as the cellular archi
 tecture. A change in microscopic properties carries over to the macroscopi
 c scale through an alteration of the mesoscopic damage and fracture mechan
 isms. To study these dependencies we have developed a multiscale modelling
  framework that takes these ingredients into account. The influence of the
  relative density\, material strain hardening\, cell shape anisotropy\, st
 ructural randomness and specimen size on the cell wall damage behavior and
  overall fracture response is analyzed in detail. Finally\, all material a
 nd architectural effects are summarized in a strength versus ductility gra
 ph\, identifying trends for improved design of metallic foams.\nRecent exp
 erimental studies have shown that metallic and graphene nanofoams can unde
 rgo dimensional changes when a potential difference is applied in an elect
 rochemical environment. The primary actuation mechanism is the electric-do
 uble layer charging of the internal surface. To account for the excess cha
 rge we have developed an atomistic model that is informed by ab-initio den
 sity functional theory calculations. To make a scale transition to the con
 tinuum scale\, we propose a surface layer model that is informed by the at
 omistic simulations. We study the charge-induced actuation strain and work
 -density of ordered and disordered nanoporous gold and graphene architectu
 res. The differences between the ordered and disordered structures are cri
 tically addressed.
LOCATION:Oatley Seminar Room\, Department of Engineering
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