A Comparative Study of AC and DC Electrorheological Material Based Adaptive Structures in Small Amplitude Vibration

The present investigation focused on the controllability and reliability of AC and DC electrorheological (ER) materials based adaptive beams. The mechanical and rheological reliability of such adaptive structures was studied over an extended time period. Modal vibration frequencies exhibited relatively stable behavior over time, while modal loss factors were observed to vary significantly. Significant structural stiffening in response to electric field was observed with the DC ER material, while damping dominated the changes observed with the AC ER material. Oscillatory shear experiments with the two materials provided insight into the cause of the observed differences between AC and DC material based structural response. At small strains both ER materials behaved in a nonlinear viscoelastic fashion. The relative contributions of nonlinear loss and storage moduli were found to cause the observed differences in the performance of these adaptive structures. The structural time response upon the application or removal of electric field was also studied. Both AC and DC structures responded rapidly to the application of electric field. For the case of electric field removal, however, it was found that the field strength and application time. ER material type. and structural excitation amplitude all influenced response time.