PREDICTION AND MEASUREMENT OF MODAL DAMPING OF LAMINATED COMPOSITE BEAMS WITH PIEZOCERAMIC SENSOR ACTUATOR

Damping factor and modal damping of carbon/epoxy laminated composite b eams with the piezoceramic sensor and actuator are predicted theoretic ally and measured experimentally Finite dement method is used for the analysis of dynamic characteristics of the laminated composite beams w ith and without the piezoceramics. The impulse technique is applied to measure the fundamental frequency, the damping ratio and the modal da mping for the first bending mode of the beams. When a pair of piezocer amics 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. Takin g into account the damping and the stiffness of the adhesive layer and the piezoceramics in the finite element modeling, damping ratio, fund amental frequency and modal damping are in good agreement with those o f the measured values. To investigate the effects of sensor/actuator d ynamics, 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 measure d values, as for the beams with piezoceramics. It is suggested that th e modal damping (2 zeta omega) is a more appropriate performance index rather than the damping ratio (zeta) 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 moda l damping is directly related to the settling time of the vibration.