Vibration Test of a Cross-ply Laminated Composite Circular Cylindrical Shell Partially Filled with Liquid

The vibration characteristics of laminated composite circular cylindrical shell partially filled with liquid was investigated and compared with the isotropic shell. Especially, the differences of the vibration characteristics between the laminated and isotropic shells and the mass effect of liquid on the vibrations of the shells were clarified experimentally. The laminated composite circular cylindrical shell was made from five cross-ply layers of CFRP prepreg. The isotropic circular cylindrical shell with the same size as the composite shell was made of steel. In the experiment, these circular shells were mounted on a vibration table with a clamped lower end and a free upper end, and excited horizontally by white noise. The vibration displacements of laminated shell were measured by non-contact optical fiber sensor, and those of steel shell was measured by eddy current sensor. The natural frequencies and mode shapes were identified by modal analysis using STAR-system software.As the results, in the case of empty shells, the frequencies of laminated shell is high compared with the ones of isotropic shell in the region of large circumferential wave number. When the shells were filled with liquid and increasing in the liquid height, however, the frequencies of laminated-shell is lower than ones of isotropic shell in that circumferential wave number region. And bulging-type modes of laminated shell having partially filled liquid appeared at small circumferential wave numbers by comparison isotropic shell.