Piezoelectricity of a microcellular polypropylene electret under an external inertial load

Microcellular polymer electrets are frequently used for sensor and actuator applications because of their strong piezoelectric effects. In the current study, the effective piezoelectric constants in the thickness direction for microcellular polypropylene (PP) electrets under external inertial loads are evaluated using a model based on the extended Hamilton's principle of linear piezoelectricity. Microcellular PP electrets are fabricated using corona discharges and the effective piezoelectric constants for, respectively, the sensor (direct) and actuator (inverse) operations of the electret are obtained through a series of mathematical treatments. In addition, aging effects are investigated to estimate the time-wise stability conditions of the poled electric charges in the electrets. Experimental results of the electrets' piezoelectricity are compared to ensure the validity of the models developed.