Dielectric response of solids for contactless detection of stresses and strains

The dielectric response of any dielectric material varies with deformations. This effect, called dielectrostriction, can be utilized for monitoring stresses and strains in elastic solids. This article introduces the concept of a planar capacitor sensor and sensor rosettes detecting deformations without mechanical contact with the monitored part. Outputs of two-sensor and four-sensor rosettes attached to isotropic material are directly proportional to the principal directions and the difference of in-plane principal strains or stresses. In this work a linearity of the stress- and strain-dielectric response is experimentally verified for uniaxially loaded specimens. The principal strains and their principal directions are measured using a four-sensor rosette. The agreement between applied and measured values is demonstrated. The developed sensing technology provides a novel approach for stand-alone sensors and a suitable solution for implementation of self-sensing stresses and strains in load-bearing structures.