Strontium Titanate Composites for Microwave-Based Stress Sensing

Composites of strontium titanate ceramic particles dispersed in epoxy resin have been manufactured for nondestructive wireless stress sensing. Magnetic coupling with a hairpin resonator on the surface of the composite was used to detect changes in the effective dielectric properties. The hairpin resonator was excited in the microwave frequency domain at 1-10 GHz, and its resonant frequency detected using a network analyzer based on the absorbed power. The results indicated a shift in the resonant frequency of the hairpin resonator under application of stress due to a change in the dielectric constant of the composite.