Characterization of delamination features of orthotropic CFRP laminates using higher harmonic generation technique: Experimental and numerical studies

In this work, the key delamination features of orthotropic CFRP laminates are investigated by the higher harmonic generation (HHG) method based on experimental and numerical approaches. A laser scanning vibrometer (LSV) is adopted for the non-contact experimental setup and an explicit 3D FEM model is proposed to facilitate the numerical simulations of underlying mechanism of HHG in CFRP. The 2D contour images are established to identify the delamination existence and the maximum response amplitude (MRA) is proposed to quantify the delamination condition. The effect of key features of delamination including the size, depth and relative orientation respect to the wave front on the nonlinear response is subsequently studied and found that the approximate location of delamination can be identified by the HHG approach and the MRA of higher harmonics is highly sensitive to the variation of delamination features. In addition, the effect of delamination features on MRA variation is briefly analyzed from the perspective of physical origin of nonlinear response. The work will enhance the detection of damage in composite structures and demonstrates the applicability of HHG technique for decoding the causality and complexity of nonlinear elasticity in delaminated composites and its potential for the comparative evaluation in defect information.