The aim of this work is to investigate the effects of debonding lengths on the static, fatigue, linear and nonlinear vibration behaviour of sandwich materials. First, a study was conducted in static and cyclic fatigue loading with various debonding lengths. Shear and flexural modulus in static tests were determined using the sandwich plate theory. The effects of debonding lengths on the stiffness, hysteresis loops and damping were studied for various numbers of cycles during fatigue tests. Then, modelling of the damping of a composite sandwich with debonding was established considering finite element analysis which evaluated the different energies dissipated in the material directions of the core and the skins. The effects of debonding variable lengths on natural frequencies and damping were studied numerically and compared with experimental results. Finally, the nonlinear vibration method was used to characterize the behaviour of sandwich beams with debonding. The nonlinear parameters corresponding to the elastic modulus and damping were determined for each frequency mode and each debonding length. The results showed that nonlinear parameters were much more sensitive to damage than linear parameters.
