Damage detection based on vibration for composite sandwich panels with truss core

Composite sandwich panels with truss core have been widely studied for their outstanding characteristics and excellent designable properties, but very little of this work was focused on non-destructive testing (NDT) methods. Based on mode curvatures and a two-dimensional (2D) continuous wavelet transform (CWT), a baseline-free NDT method is proposed for damage identification in these types of sandwich panels. Initially, the 2D CWT is applied to process the mode curvatures from specific mode shapes. Then, considering the structural periodicity of the truss, which is a distinctive characteristic of these sandwich panels, a novel damage index is defined through a combination of the structural periodicity and the coefficients of the CWT. Numerical simulations and experimental tests were conducted to identify damage in the composite sandwich panels with core trusses forming a pyramidal lattice. Results show that the proposed method is efficient and reliable, and has a good resolution in identifying one or more truss bars missing detection without a baseline and thus has the potential in damage detection of composite sandwich panels.