Detection of deformation induced electromagnetic radiation from cement- barium titanate composite under impact loading

Abstract

Electromagnetic radiation (EMR) responses from cement–BaTiO3 (BT) composites under impact loading have been presented in this paper. The bulk density, dielectric constant and piezoelectric charge coefficient of the cement-BT composites are observed to increase while the loss tangent decreases with increase in BT content in the composites. Measurements have been carried out using cylindrical, semi-cylindrical and quarter cylindrical antennae. Marked enhancement in the values of EMR voltage for all experiments at different heights of impact and with different antennae is observed as the content of BT is increased from 5% to 40% in the cement–BT composites. The EMR voltage increases, respectively from 0.58 V to 1.16 V, 384–732 mV and 259–520 mV for cylindrical antenna, semi-cylindrical antenna and quarter cylindrical antenna with the increase in BT content from 5% to 40% in cement–BT composites at the same level of impact (height of impact = 21 cm). Also average EMR energy release rate increases from 0.00007 V2–sec/sec to 0.00047 V2–sec/sec, 0.000065 V2 – sec/sec to 0.000214 V2 – sec/sec and 0.000032 V2 – sec/sec to 0.000135 V2 – sec/sec with the increase in BT content from 5% to 40% in cement–BT composites impacted from a height of 21 cm as measured by cylindrical antenna, semi-cylindrical antenna and quarter cylindrical antenna respectively. The EMR voltage is observed to decrease smoothly initially and then attain constancy with increase in distance of measurement location from the sample. In addition, the EMR responses were found to be proportional to the height of impact in all the cement–BT composites indicating that EMR measurement technique can effectively be used for structural health monitoring.