The aim of this paper is to study the dynamics of partially interacting composite beams subjected to axial loads. The eigenfrequencies are derived for the simply supported composite beam subjected to an axial force. Measurements of the fundamental frequencies of a simply supported composite beam consisting of three layers connected by shear connectors are carried out considering different values of the applied axial force. The agreement between the theoretical and experimental results is discussed. It is also shown that the application of the axial force introduces frictional moments at the boundaries, which make the experimental boundary conditions deviate somewhat from those of an ideal simply supported beam.