This paper investigates the nonlinear dynamic behavior of a cantilever beam made of composite material without and with lumped mass fixed along its length. The analysis compares the results coming from analytical and numerical modeling with experimental observations. The first part focuses on the analytical model. The model takes into account the nonlinearity derived from large amplitude vibration and inertia. The second part deals with the experimental test, where the specimen and the data acquisition are defined. Then, the nonlinearity of the acquired data is determined by the fitting time history (FTH) technique. The third part deals with the finite element model. Finally, the results obtained by the analytical method, the experimental method, and the numerical method are compared between each other.