Prediction and Measurement of Modal Damping of Laminated Composite Beams with Piezoceramic Sensor/Actuator

Damping factor and modal damping of carbon/epoxy laminated composite beams with the piezoceramic sensor and actuator are predicted theoretically and measured experimentally. Finite element method is used for the analysis of dynamic characteristics of the laminated composite beams with and without the piezoceramics. The impulse technique is applied to measure the fundamental frequency, the damping ratio and the modal damping for the first bending mode of the beams. When a pair of piezoceramics is attached to the clamping side of the beam as a sensor and an actuator, the damping and the stiffness of the beam are changed. Taking into account the damping and the stiffness of the adhesive layer and the piezoceramics in the finite element modeling, damping ratio, fundamental frequency and modal damping are in good agreement with those of the measured values. To investigate the effects of sensor/actuator dynamics, vibration analysis of the beam without piezoceramics is also carried out. Damping ratio, fundamental frequency and modal damping of the beams without piezoceramics agree very well with those of measured values, as for the beams with piezoceramics. It is suggested that the modal damping (2w) is a more appropriate performance index rather than the damping ratio (O) for the vibration suppression in the structure, since one of the goals of structural vibration control is to suppress vibrational amplitude as fast as possible and the modal damping is directly related to the settling time of the vibration.