Delamination monitoring in CFRP laminated plates under noisy conditions using complex-wavelet 2D curvature mode shapes

Delamination monitoring in carbon fiber reinforced polymer (CFRP) laminated plates is crucial to ensure the integrity and safety of the structures that accommodate the plates. To identify delaminations in CFRP laminated plates, the two-dimensional (2D) curvature mode shape method is a prevailing method that features instant and simultaneous determination of the presence and location of the delamination. However, this method has two noticeable deficiencies in characterizing incipient small-sized delaminations, namely lack of damage sensitivity and inadequate noise robustness. To this end, this study proposes a new dynamics feature of the complex-wavelet 2D curvature mode shape to discriminate small-sized delaminations. This feature is delicately formulated based on the integration of the 2D curvature mode shape with the complex wavelet. The complex-wavelet 2D curvature mode shape is superior to the 2D curvature mode shape by virtue of its stronger damage sensitivity and noise robustness. These merits can be attributed to the adjustable localization and the multi-scale properties of the second-order Gabor wavelet, respectively. Proof of concept of the complex-wavelet 2D curvature mode shape is numerically undertaken in a finite-element laminated CFRP plate with a small-sized delamination, with emphasis on sensitivity to damage and robustness against noise. The applicability of the feature is experimentally validated on a CFRP laminated plate with a small-sized delamination, whose mode shapes are acquired via the non-contact measurement using a scanning laser vibrometer. The numerical and experimental results show that the complexwavelet 2D curvature mode shape can effectively designate the presence and location of the delaminations in CFRP laminated plates under noisy conditions.