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Spring 2011

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Theory of dielectric elastomers

In response to a stimulus, a soft material deforms, and the deformation provides a function. We call such a material a soft active material (SAM). This review focuses on one class of soft active materials: dielectric elastomers. Subject to a voltage, a membrane of a dielectric elastomer reduces thickness and expands area, possibly straining over 100%. The phenomenon is being developed as transducers for broad applications, including soft robots, adaptive optics, Braille displays, and electric generators.

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Finite Deformation: Special Cases

The notes on finite deformation have been divided into two parts: special cases and general theory (node/538). In class I start with special cases, and then sketch the general theory. But the two parts can be read in any order.

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Free Energy

For a system in thermal contact with the rest of the world, we have described three quantities: entropy, energy, and temperature. We have also described the idea of a constraint internal to the system, and associated this constraint to an internal variable.

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Poroelasticity, or migration of matter in elastic solids

A sponge is an elastic solid with connected pores. When immersed in water, the sponge absorbs water. When a saturated sponge is squeezed, water will come out. More generally, the subject is known as diffusion in elastic solids, or elasticity of fluid-infiltrated porous solids, or poroelasticity. The theory has been applied to diverse phenomena. Here are a few examples.

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Pressure

So far we have been mainly concerned with systems of a single independent variable: energy (node/4878). We now consider a system of two independent variables: energy and volume. A thermodynamic model of the system is prescribed by entropy as a function of energy and volume.

The partial derivatives of the function give the temperature and the pressure. This fact leads to an experimental procedure to determine the function for a given system.

The laws of ideal gases and osmosis are derived. The two phenomena illustrate entropic elasticity.

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Engineering Sciences 241: Advanced Elasticity

This is a second graduate course in solid mechanics.  Building on thermodynamics and linear algebra, the course explores coupled mechanical, thermal, electrical, and chemical actions.  The course draws heavily upon phenomena in soft active materials.

This page is updated for ES 241 taught in Fall 2017 (See also Google doc for lecture-by-lecture record and homework)

The course taught in the past:

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