Backside delamination detection in composites through local defect resonance induced nonlinear source behavior

Abstract

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Nonlinear local wave-direction estimation for in-sight and out-of-sight damage localization in composite plates

“…In addition, the plate with BVID is covered with removable reflective tape (3M™ Scotchlite™ 680CRE10). This was required to be able to detect the nonlinear vibrational components which are of low J o u r n a l P r e -p r o o f amplitude [23,37,38]. In both cases, the propagation of the fundamental anti-symmetric Lamb mode (A 0 ), which has a dominant out-of-plane surface velocity response, is investigated.…”

“…One speaks about nonlinear elastic wave spectroscopy (NEWS) [24][25][26][27][28][29][30] or nonlinear elastic wave modulation spectroscopy (NEWMS) [31][32][33][34][35][36], when there is a single excitation or when there are multiple excitation signals, respectively. Very recently, the current authors used J o u r n a l P r e -p r o o f (numerical as well as experimental) NEWS to show that the nonlinear response at the defect can be used for the detection of shallow damages and, more important, deep backside delaminations [37,38]. It was observed that defects act as secondary sources of higher harmonic vibrational components which can be measured at a distance from the defect's location.…”

Nonlinear Elastic Wave Energy Imaging for the Detection and Localization of In-Sight and Out-of-Sight Defects in Composites

“…However, an increased activity at the defect is seen in both the second and the third higher harmonic components (Figure 5g,h, respectively). The efficient generation of nonlinear components at the deep defect is related to LDR of the thin material section between the delamination and the backside [34].…”

Broadband nonlinear elastic wave modulation spectroscopy for damage detection in composites

“…Current authors showed that a backside delamination (i.e. defect's depth > 80% of the sample's thickness) acts as a secondary source of higher harmonics when the excitation frequency matches the defect's backside LDR frequency [40]. In order to increase the nonlinear response at the defect, a second excitation source can be added.…”