Dynamic Numerical Modeling and Simulation of Interfacial Cracks in Sandwich Structures for Damage Detection

Dynamic modeling of interfacial cracks between the skin and core materials was performed and numerical simulation was undertaken to study the feasibility of crack detection. The cracks were modeled in the way as they were physically in the sandwich beam structures using the finite element method. Numerical simulation of impact-hammer hit was applied to the finite element models to calculate the time history of strain responses along the sandwich beams. Dynamic crack opening and closure was considered with friction at the surfaces of interfacial cracks. Thus, nonlinear dynamic analysis was conducted. Then, the Fast Fourier Transform (FFT) was used to transform the time responses to frequency responses. The effects of interfacial cracks were examined in both time and frequency plots by comparing those responses between the damaged structure and the intact structure. The present study showed that the effect of crack closure was important so that nonlinear analysis was necessary to represent the interfacial crack behaviors properly. The strain response from nonlinear dynamic analysis (i.e. simulated impact hammer hit) had great potential for detecting and locating a small size of interfacial crack in a sandwich beam structure.