Characterization of sandwich beams with debonding by linear and nonlinear vibration method

The nonlinear vibration method is used to characterize the behavior of sandwich beams with debonding. The technique focuses on the response of the material's resonance modes as a function of the driving amplitude by sweeping the frequency at various drive levels. Sandwich material used in this study is constructed with glass fibre laminates as skins and with PVC closed-cell foams as core. For an undamaged specimen, the resonance frequency does not change with increased excitation amplitude. For a damaged specimen, the resonance frequency decreases and the inverse quality factor (loss factor) increases proportional with the increasing excitation amplitude. 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.