Investigation of vibrational characteristics of composite beams with fluid–structure interaction

The study examined the effect of fluid–structure interaction on global dynamic properties such as vibrational frequency, mode shape, modal curvature, as well as free vibrational responses along E-glass composite, carbon composite, and aluminum beams, respectively. The digital image correlation technique was used to measure the free vibrational responses along the beams in air and water, respectively. The vibration submerged in water exhibited higher frequency modes than the dry vibration under the same excitation. Experimental modal analysis showed that the mode shapes were very close for an aluminum beam with and without the FSI effect while there was a modest difference for a carbon composite beam because the FSI effect is greater for the composite beam. Modal curvatures for the both beams are more influenced by FSI, especially for the composite beam. The curvature is directly related to the bending strain of the beam. This explains why the difference in strains measured for composite structures in air and water, respectively, varies significantly from location to location of the structures under impact loading. One location has much greater difference in strains than another location. The FSI can change potential failure locations of the composite structures because of the change in modal curvatures.