Characterization of multilayer delaminations in composites using wavenumber analysis: numerical and experimental studies

Delamination is one of the most common and dangerous failure modes for composites because it takes place and grows in the absence of any visible surface damage. The successful implementation of delamination detection in aerospace composite structures is always challenging due to the general anisotropic behavior of composites and multilayer delamination scenarios. This article presents a numerical and experimental investigation to detect and characterize the multilayer delaminations in carbon fiber-reinforced polymer composite plates using guided waves and wavenumber analysis. Multiphysics three-dimensional finite element simulations of the composite plate with five different delamination scenarios are conducted to provide the out-of-plane wave motion for wavenumber analysis. The out-of-plane results from finite element simulations of one delamination and two delaminations are validated by the scanning laser Doppler vibrometer measurements. It is found that the wavenumber analysis can identify the plies between which the delamination occurs and evaluate the delamination severity by comparing the new wavenumbers due to the trapped waves in the delamination regions, which is potentially related to delamination severity. Both numerical and experimental results demonstrate a good capability for the detection and characterization of multilayer delaminations in composite structures.