A quasi-static (low frequency) model is developed for THUNDER actuators configured as displacement sensors based on a simple Raleigh–Ritz technique. This model is used to calculate charge as a function of displacement. Using this and the calculated capacitance, voltage versus displacement and voltage versus electrical load curves are generated and compared with measurements. It is shown that this model gives acceptable results and is useful for determining rough estimates of sensor output for various loads, laminate configurations and thicknesses.