Capacitive compressive stress self-sensing behavior of cement mortar and its dependence on the thickness

Capacitance based compressive stress/strain self-sensing properties and its dependence on thickness is presented for the fist time. Coplanar electrode configuration is used for the electrical measurements and known weights are used to create cyclic stresses on the mortar samples with different thicknesses. Mortar plates with 6 mm, 10 mm and 15 mm thicknesses are produced and capacitance change with stress application is measured with an inductance-capacitance-resistance meter (LCR meter). Capacitance value of the mortar with 6 mm, 10 mm and 15 mm thicknesses are 450 pF, 532 pF and 607 pF, respectively. Capacitance increases as thickness increases. However, stress sensitivities of the mortar with 6 mm, 10 mm and 15 mm thicknesses are measured as 3.1 x 10-6 P-1, 3.1 x 10-7 P-1 and 1.1 x 10-7 P-1. Stress sensitivity decreases with increasing the mortar thickness. While capacitive self-sensing is effective when the mortar thickness is known, capacitive self-sensing is ineffective with varying mortar thickness. This research contributes valuable insights into the practical application of capacitance-based sensing in materials subjected to compressive stresses, highlighting the need for considerations regarding thickness variations in real-world applications such as load monitoring and weighing.