Characterization of delamination by using damage indices

A damage index based on in-plane modal strain is developed to characterize the dynamic behavior of laminated composite plates of arbitrary thickness with discrete multiple delaminations. A recently developed improved layerwise laminate theory is used to accurately describe the displacement field and capture the transverse shear effects for the moderately thick plates. The multiple seeded delaminations are modeled using Heaviside step functions. The performance of the damage index is compared to previously developed damage indices. Numerical results indicate that the newly developed damage index is able to identify the location and the extent of delamination more accurately and more consistently, compared to other indices, in plates with small discrete multiple delaminations. Experiments using a Scanning Laser Doppler Vibrometer (SLDV) and strain gauges are conducted and the results obtained agree well with the numerical results.