Changing dielectric properties of an elastically deformed solid material is called dielectrostriction. This physical
response enables a concept of self-sensing in dielectric materials such as polymers and polymeric composites. In
addition, dielectrostriction response is governed by same material parameters as the electrostriction effect which is
suitable for self-actuation applications. Designed planar capacitor sensor is employed for monitoring dielectrostriction
effect without mechanical contact with a loaded specimen. Such sensor can also be arranged in a rosette to directly
obtain the principal values of the stress/strain and the principal directions. This study investigates dielectrostriction and
electrostriction effects in carbon nanotube (CNT) composites. Preliminary results show tenfold increase in
dielectrostriction response of nanocomposites having 2 vol. % of randomly distributed CNTs. Current study targets
CNT composites having microstructure modified using applied electric field for optimizing sensing and actuation
A variation of dielectric response with deformation, called dielectrostriction, provides a new approach for in-line monitoring properties and structure of materials. The dielectrostriction effect resembles a well-known birefringence phenomenon which has been widely used for NDE of transparent materials. While birefringence is described by the stress-optic rule, the stress-dielectric rule applies to dielectrostriction. However, dielectrostriction measurements can be applied to both transparent and opaque dielectric materials, require a much simpler measurement technique, are capable of measuring local stresses/strains and can be implemented for material processing and health monitoring of structures. Planar capacitor sensor setup is implemented to detect the dielectrostriction effect in both liquid and solid polymers. Dielectrostriction effect and the stress-dielectric relationship are studied for solid polycarbonate subjected to uniaxial tensile load. Similar results are obtained for liquid polymers in oscillatory shear flow.
A novel approach for NDE of polymeric materials utilizing the dielectrostriction effect is presented. Any dielectric material exhibits dielectrostriction effect which is defined as variation of dielectric properties of the material with deformation. This phenomenon resembles well known photoelastic effect which has been widely used for NDE of transparent materials. The major difference is that dielectrostriction measurements can be conducted using a lower frequency than optical range of electromagnetic field. Thus, the dielectrostriction measurements can be administered to any, even non-transparent, material for in-line monitoring of strains and stresses. In addition, no mechanical contact is required for dielectrostriction measurements. Therefore, there is no problem with interface and attachment of the sensing element to the monitored part. A potential of dielectrostriction phenomenon for NDE is not completely explored at this time and would be the subject of future extensive studies. We will show its feasibility for monitoring undesirable features such as fatigue, cracks and residual stresses in dielectric materials. In this paper, we will present theoretical background and experimental data for dielectrostriction study of polymeric parts manufactured under various processing conditions.