Coda wave interferometry for the measurement of thermally induced ultrasonic velocity variations in CFRP laminates

Abstract

Ultrasonic velocity measurement is a well-established method to measure properties and estimate strength as well as detect and locate damage. Determination of accurate and repeatable ultrasonic wave velocities can be difficult due to the influence of environmental and experimental factors. Diffuse fields created by a multiple scattering environment have been shown to be sensitive to homogeneous strain fields such as those caused by temperature variations, and Coda Wave Interferometry has been used to measure the thermally induced ultrasonic velocity variation in concrete, aluminum, and the Earth's crust. In this work, we analyzed the influence of several parameters of the experimental configuration on the measurement of thermally induced ultrasonic velocity variations in a carbon-fiber reinforced polymer plate. Coda Wave Interferometry was used to determine the relative velocity change between a baseline signal taken at room temperature and the signal taken at various temperatures. The influence of several parameters of the experimental configuration, such as the material type, the receiver aperture size, and fiber orientation on the results of the processing algorithm was evaluated in order to determine the optimal experimental configuration.

Application of Ultrasonic Coda Wave Interferometry for Micro-cracks Monitoring in Woven Fabric Composites

“…When the effective velocity change is local, or at least not distributed over the area where the CWI method is sensitive, the time lag could deviate from a linear evolution. This relation is experimentally verified in several works when considering a pure dilatation of the materials under thermal effects [19,24] or studying weak stress effect in heterogeneous samples such as concrete [25].…”

“…Here, all the raw signals (coda part) have the same total length T t = 400µs and sampling time Δt = 0.002 µs. As mentioned in [16,19] when the perturbation in the sample is small, the relative velocity change of the coda part in the signal can be considered as constant. In this configuration the time lag increases linearly with the arrival time.…”

“…Recently, Zhu et al [17] have used coda waves to determine internal stress in a polymer composite. Livings et al [19] investigated the feasibility of coda waves to estimate the thermally induced ultrasonic velocity variation in a plexiglas plate and in a carbon fiber reinforced polymer composite plate.…”

The installation of embedded ultrasonic transducers inside a bridge to monitor temperature and load influence using coda wave interferometry technique

“…The high sensitivity of the CWI method has been validated in detecting stress-induced velocity change, 22,40,41 temperature variation, 42–44 water saturation, 38,45 and early-stage damage. 22,23,46 The CWI method has also been applied for damage localization and imaging purposes.…”

“…Various studies have shown the linear relationship between wave propagation velocity change and temperature variation. 42,43,49,50 Thus, the thermally induced velocity change during each truck position can be calculated by equation (4), where T(p) is the temperature at the time when the truck was placed in different positions p and Tstart is the temperature measured before the load test start…”