Abstract: Firstly， according to the anisotropic characteristics of composite beams， the vibrational function of each sub beam was expressed by substructure analysis method， and the theoretical solution principle of the natural frequency of composite beams was clarified. Secondly， based on Matlab software， an analysis process of the natural frequency was proposed and the calculation program was coded . Finally， an experimental application toward TC500 carbon fiber/resin matrix composite beam was carried out， that the natural frequencies of fiber-reinforced composite beam with non-overlapping delaminations were measured under the same boundary condition based on the established natural frequency test system. It was found that the natural frequencies decreases gradually as the delamination number increasing. Meanwhile， with the increase of modal orders， the influence of delaminations on the natural frequencies became more obvious. Furthermore， the related errors were within the range of 1.06%~ 5.49% by comparing experimental results with calculated results， which have verified the validity of the analysis method.

Key words: natural frequency, fiber-reinforced, composite beam, non-overlapping delaminations, experimental analysis