Identification of composite materials elastic moduli from Lamb wave velocities measured with single sided, contactless ultrasonic method

Selective generation of Lamb wave modes and their propagation characteristics in defective composite laminates

“…… … … HQ dV (20) Substituting equation (19) into equation (20) and applying Gauss' theorem leads to [41] Yˆd 31 E PZT 4p(1 ¡ n PZT ) … … (e r 0 ‡ e y 0 )r 0 dr 0 dy 0…”

“…During manipulation, directionality and contact are among basic issues that may considerably in uence the detection effectiveness. Motivated by this, substituent non-contact devices, such as air-coupled [18,19] and uid-coupled [20] transducers or electromagnetic acoustic transducers (EMATs) [21,22], were invented. However, air-or uid-coupled transducers can suffer from a relatively low ef ciency because of the large differences in mechanical impedances between the air/ uid and the objects under detection.…”

Ultrasonic guided waves for health monitoring of high-pressure composite tanks

“…The use of the Lamb mode-based inverse routine [13] mentioned in the previous section showed that the measured relative changes in the attenuation of the A 0 mode propagating along x 2 correspond to similar relative changes of the imaginary part of the modulus C 66 (or C 55 if the mode is propagating along x 3 ), which is in fact the Coulomb modulus in the plane of propagation P 12 (or P 13 ). These nominal changes in C 00 kk (k ¼ 5 or 6) are indicated in Table 1, together with the complex C ij measured for plane P 12 (similar data have been obtained for plane P 13 because the tested sample is a crossed-ply specimen).…”

“…These indicate that low temperatures cause microcracking within some plies of the material. The inverse routine based on Lamb mode measurements [13] mentioned above allowed showing that this general increase in the wave-numbers, between the initial state and the last immersion at À196 1C, corresponds to a decrease of about 15% of all the elastic moduli C 0 ij . This confirms previous studies, which have shown that very low temperatures cause damages to composite materials, which can be monitored using Lamb waves [3,14,15].…”

“…), the inversion process may be used to infer these properties. This consists of adjusting the adequate parameters for optimizing the fit between the predicted and measured wavenumbers and/or attenuations [13].…”