Stiffness measurement and defect detection in laminated composites by dry-coupled plate waves

Lamb wave characterization of the effects of long-term thermal-mechanical aging on composite stiffness

“…͑5͒ were computed in a similar manner from data obtained for propagation in the 90°direction. Further details of the velocity and stiffness measurements using this technique can be found in Huang et al 15 The Lamb wave scanning system was used to measure time of flight, velocity, and stiffness in the 0°and 90°direc-tions on one unaged and three aged specimens. For the measurements, a four-cycle Gaussian-enveloped sine wave was used to generate the signal and the received signal was captured at sampling rate of 25 MHz.…”

“…The measurement technique has been shown to be sensitive to changes in bending stiffness caused by mechanical degradation such as impact damage, delaminations, and debonds. 15 The scanner can also be used to monitor stiffness variations created during manufacturing which may be due to changes in fiber volume content, porosity content, or due to process control variables.…”

“…The velocity measurements are accurate and repeatable to within 1%, resulting in reconstructed stiffness values repeatable to within 4%. 15 A mechanical scanner, shown in Fig. 1, is used to move the sensors over the surface to map the time of flight, velocity, or stiffnesses of the entire specimen.…”

Lamb wave assessment of stiffness degradation in fatigued composites

“…(4) in order to produce the best fit the experimental data. The velocity measurements are accurate and repeatable to within 1% resulting in reconstructed stiffness values repeatable to within 4% [12]. A mechanical scanner is used to move the sensors over the surface to map the time-of-flight, velocity, and stiffness of the entire specimen.…”

Lamb Wave Stiffness Characterization of Composites Undergoing Thermal-Mechanical Aging

“…The same peak in the waveforms received at various distances is used to measure the time difference between the signals. The velocity measurements are accurate and repeatable to within 1 % resulting in reconstructed stiffness values repeatable to within 4% [5]. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve.…”