Free vibration analysis of a delaminated beam–fluid interaction system

• A delaminated composite beam partially contacting with a fluid is studied.
• The analytical solution has been presented for the vibration characteristics.
• The effect of different parameters on the natural frequencies and corresponding mode shapes are examined.

A delaminated offshore structure having the form of a laminated composite beam partially contacting with a fluid is considered and its free vibration characteristics are presented in this paper. The delaminated beam is modeled as a uniform Bernoulli–Euler cantilever beam fixed at the bottom. The beam is analyzed as five interconnected sub-beams in which the continuity and compatibility conditions are satisfied between adjoining beams. Transverse displacements of the beam are approximated by a set of admissible trial functions which are required to satisfy the boundary, continuity and compatibility conditions. Based on the eigen-value technique, the solution for the natural frequencies and the corresponding mode shapes are obtained. The numerical results have been compared with the existing results and a close agreement is achieved. Furthermore, the effect of different parameters including free surface wave, the fluid density and material anisotropy on the natural frequencies of the delaminated beam based on the free and constrained modes are examined and discussed in detail.