Non-destructive testing of glass fibre reinforced plastics with a full polarimetric imaging system

Comparison of nondestructive testing techniques for the inspection of wind turbine blades' spar caps

“…Radar transmission measurements using frequency bands of ~24 GHz showed a high penetration depth in glass fiber‐reinforced materials and the possibility to detect water pockets inside the rotor blade . Terahertz waves were explored as an NDT tool for identifying and characterizing flaws and damage in nonconducting composites and conducting composites using both time‐domain spectroscopy and continuous wave approaches . Terahertz techniques were used for detecting delamination defects in panels simulating the WT blade structure, proving the capability to highlight flaws as thick as 1 × 10 −3 m. Furthermore, previous investigations into the use of terahertz synthetic aperture radar systems operating at around 100 GHz have indicated that the use of fully polarimetric systems can lead to improvement in the image quality .…”

“…Previous investigations into terahertz imaging as an NDT technique indicate that this method has the potential to detect some fiberglass defects. Those examinations included several terahertz imaging methods such as time‐domain spectroscopy and frequency‐modulated continuous wave systems . Additionally, preliminary investigations into terahertz ISAR have also shown that there are added benefits as this technique is coupled with a fully polarimetric system .…”

A review of microwave testing of glass fibre-reinforced polymer composites

“…In the radar intensity image for 2 mm deep below surface, the dry fibre fabric was shown due to the difference in the dielectric properties of the glass fibres and the rest of the GFRP component and an increased surface roughness at the dry fibre region. (b) Synthetic aperture radarNezadal et al[92,93] employed a W-band SAR system to identify flat bottom holes in GFRP samples. These holes had different diameters (5, 10, 15 and 20 mm) and depths (from 0.5 to 14.5 mm), and the overall thickness of the composite plate was 15.0 mm.…”

Active Millimeter-Wave Radiometry for Nondestructive Testing/Evaluation of Composites—Glass Fiber Reinforced Polymer

“…Other EM methods include free space microwave NDT using horn lens antennas with a network analyzer [8] and the use of inter-digit sensor to measure the Sparameters along a defected surface [9]. Polarization studies on a GFRP sample using a synthetic aperture radar technique is reported in [10]. Table I and II presents an overview of some specific research published in the field of NDT/E.…”