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SUMMARY:Geometry and mechanics of liquid crystal elastomers - Dr John Bigg
 ins\, University of Cambridge 
DTSTART:20230602T140000Z
DTEND:20230602T150000Z
UID:TALK199546@talks.cam.ac.uk
CONTACT:Jamie Clarkson
DESCRIPTION:Liquid crystal elastomers (LCEs) are rubbery soft solids that 
 contain the orientational order of a liquid crystal. They exhibit an align
 ed-isotropic phase transition\, which is associated with a very large spon
 taneous contraction along the alignment (~50%)\, making LCEs promising art
 ificial muscles. In this talk\, I will give an introduction to LCEs\, and 
 discuss three recent mechanics problems arising from our work on them. One
  key idea is a flat LCE sheet can be fabricated with a pattern of molecula
 r alignment\, which turns into a pattern of contraction upon stimulation\,
  morphing the sheet into a (Gauss) curved surface - i.e. LCEs can be used 
 to form programmable shape-shifting devices. The material is the machine. 
  A concentric circle pattern will morph the sheet into a conical shell\, a
 nd such samples are surprisingly strong actuator capable of lifting 1000x 
 their own weight. This leads to my first mechanics problem: how much load 
 can such a conical shell bear without buckling. I will discuss that LCE co
 ne buckling is actually accelerated by boundary layer deformations\, which
  leading to a new buckling formula with a t^2.5 scaling with thickness\, a
 s compared to t^2 for classic Koiter like results. Secondly\, I will discu
 ss how to design patterns of contraction to create surfaces with curved fo
 lds\, which are  analogues of the curved folds found in origami\, except w
 ith a geometrically intrinsic character\, and hence much greater strength.
  Finally\, I will discuss the "soft-elasticity" of LCEs --- a phenomenon i
 n which the alignment rotates in response to strain\, leading to large def
 ormations at almost zero stress. I will demonstrate how such soft-modes le
 ad to interesting microstructures in the material and\, and generate a new
  surface instability that forms large amplitude cross-hatch topography.\n\
 n\nJoin Zoom Meeting\n\nhttps://eng-cam.zoom.us/j/83729338532  \n\nMeeting
  ID: 837 2933 8532\n\n
LOCATION:CivEng Seminar Room (1-33) (Civil Engineering Building)
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