<title>Actuating power capacities of polymers, gels, and composites for use in smart materials systems</title>

Abstract

The potential of using volume and shape changes of polymers, gels, and composites as a source of actuating power was evaluated. For an ordinary polymer, volume changes may be induced by simple heating and cooling (thermal expansion) or by allowing the polymer to undergo physical transitions such as glass transition, melting or crystallization, and solid state phase transformation. Shape changes in shape memory polymers may be obtained by a combination of thermal and deformation treatments. Polymer gels may undergo large continuous or discrete volume changes in response to stimuli such as temperature, solvent concentration, pH value, electric field, and light. A composite/bimetal laminate, when configured in a proper stacking sequence, is capable of generating out-of-plane forces or deflections. When constrained from changing the volume or shape, each class of these materials can exert a great counteracting stress or pressure on the constraining body. when free to expand or contract, the material may be prescribed to undergo a large change in volume or shape. The magnitudes of the counteracting stresses and the percentages of achievable volume or shape changes were calculated for several commonly used gels, piezopolymers and composites/bimetals. Methods and procedures for making these calculations were established.