The Characterization of Compliant Active Materials

Professor Andrew Douglas
Department of Mechanical Engineering, Johns Hopkins University

Date:  November 9, 1999
Time:  3:30 p.m.
Place:  W128 Nebraska Hall


There are a number of applications in which compliant active materials, such as certain polymer gels, can be used as innovative sensors and actuators.  However, unlike their stiffer counterparts (such as traditional piezoelectric crystals), the mechanical properties of these materials have not been studied extensively.  Indeed, there are a number of complex issues involved in properly characterizing these materials.  The ability of these materials to achieve large elastic deformations requires a finite, rather than linear, elastic approach.  Consideration must also be given to the manner in which these materials respond to environmental changes, such as variations in pH level.  Furthermore, viscoelasticity is often a concern in compliant active materials.

This talk will outline the experimental and analytical challenges that are faced in trying to characterize compliant active materials.  Our biaxial testing apparatus will be reviewed and the methods for materials fabrication explained.  The analytical framework developed for characterizing these materials will be presented with special emphasis on a finite elastic approach using non-traditional invariants.