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Graeme Milton
Department of Mathematics, University of Utah
Composite materials: An old field of study full of new surprises
Tuesday 11th May 14:05-15:55pm,
Carslaw Building Room 250.
Composite materials have been studied for centuries, and have
attracted the interest of reknown scientists such as Poisson, Faraday,
Maxwell, Rayleigh, and Einstein. Their properties are usually not just
a linear average of the properties of the constituent materials and
can sometimes be strikingly different. The beautiful red glass one
sees in old church windows is a suspension of small gold particles in
glass. Sound waves travel slower in bubbly water than in either water
or air. In the last few decades composites have been found to have
some surprising properties. Most materials, such as rubber, get
thinner when they are stretched, but it is possible to design
composites which get fatter as they are stretched. Electromagnetic
signals can travel faster in a composite than in the constituent
phases. It is possible to combine materials which expand when heated
to obtain a material which contracts when heated. Similarly it is
possible to combine materials with positive Hall coefficients to get a
composite with negative Hall coefficient. It is still an open question
as to what properties can be achieved when one mixes two or more
materials with known properties. This lecture will survey some of the
progress which has been made.
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