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SUMMARY:Magnetorheological elastomers: from micro-deformation mechanisms t
 o macroscopic instabilities and applications - Dr Kostas Danas\, École po
 lytechnique
DTSTART:20151023T130000Z
DTEND:20151023T140000Z
UID:TALK60494@talks.cam.ac.uk
CONTACT:Ms Helen Gardner
DESCRIPTION:Magnetorheological elastomers (MREs) are ferromagnetic particl
 e impregnated rubbers whose mechanical properties are altered by the appli
 cation of external magnetic fields. In addition\, these composite material
 s can deform at very large strains due to the presence of the soft polymer
 ic matrix without fracturing. From an unconventional point of view\, a rem
 arkable property of these materials is that while they can become unstable
  by combined magneto-mechanical loading\, their response is well controlle
 d in the post-instability regime. This\, in turn\, allows us to try to ope
 rate these materials in this critically stable region. These instabilities
  can lead to extreme responses such as wrinkles (for haptic applications)\
 , actively controlled stiffness (for cell-growth) and acoustic properties 
 with only marginal changes in the externally applied magnetic fields. Unli
 ke the current modeling of hierarchical composites\, MREs require the deve
 lopment of advanced coupled nonlinear magneto-mechanical models in order t
 o tailor the desired macroscopic instability response at finite strains.\n
 \nIn this work\, we study the response of such an assembly subjected to tr
 ansverse magnetic fields and in-plane stresses. The film is made up of a t
 ransversely isotropic MRE material\, whose energy density has been obtaine
 d experimentally\, while the substrate is a non-magnetic isotropic pure po
 lymer/gel. An analytical solution to this problem is presented in 2D\, whi
 ch shows that for adequately soft substrates there is a finite-wavelength 
 buckling mode under a transverse magnetic field. Moreover\, the critical m
 agnetic field can be substantially reduced in the presence of an adequatel
 y large compressive prestress of the assembly\, thus opening the possibili
 ty of controlling haptic interfaces with low magnetic fields.\n\n\nShort B
 iography\n\nKostas Danas was born (1981) and raised in Kozani\, Greece and
  studied at the Department of Mechanical Engineering at the University of 
 Thessaly\, Volos\, Greece where he received his Dipl. Ing. (2003) with hig
 hest honors (rank 1st). He received his M.Sc (2004) from the University of
  Pennsylvania and his Ph.D. (2008) from the University of Pennsylvania and
  the Ecole Polytechique\, France. After the end of his graduate studies\, 
 he moved to the University of Cambridge as a postdoctoral Research Associa
 te. In 2009\, he applied for a research faculty position at the Centre Nat
 ional de la Recherche Scientifique (C.N.R.S.) where he was ranked 1st in t
 he section of solid mechanics and he obtained a tenured Research Professor
  position at Ecole Polytechnique\, France in the Laboratory of Solid Mecha
 nics (LMS). His main research interests are in the field of solid mechanic
 s and composite materials with an emphasis on the theoretical and numerica
 l description of constitutive laws for composites. He is currently working
  on the modeling of microstructured active elastomers as well as on the fr
 acture of metallic porous materials.\n\nPersonal web page:  http://hera.po
 lytechnique.fr/users/kdanas\nEmail: kdanas@lms.polytechnique.fr\n
LOCATION:Oatley Seminar Room\, Department of Engineering
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