2017 Volume 43 Issue 3 Pages 112-119
Ultrasonic waves are applied to detection of uncured regions in glass-fiber reinforced plastic (GFRP) plates. Polymer-based composites play an increasingly important role in the field of civil engineering because of their high specific stiffness, strength, and excellent corrosion resistance. For example, GFRP pipes are used to rehabilitate aged sewerage pipes. Uncured GFRP tubes are inserted in the aged pipes, and are then inflated and cured with steam blowing to create close-fit pipes. In this cured-in-place pipe (CIPP) method, an uncured region may be left in the GFRP pipe, so the constructed pipe must be inspected to ensure the integrity of the reinforcement. In this study, for detection of such an uncured region in GFRP structures, the effect of resin cure on ultrasonic propagation characteristics is investigated experimentally. Through-thickness and in-plane ultra-sonic measurements are conducted, and their sensitivities to resin cure are compared. In addition to wave attenuation and velocity, several AU parameters are evaluated from the power spectrum of a broadband signal. It is found that the A2 parameter, which represents the centroid of the power spectrum, has a good correlation with the mechanical properties of GFRP plates, and is expected to improve the detectability of uncured regions.
