Ultrasonic imaging for bulk microstructure of carbon fiber woven composites

The ultrasonic reflection coefficient |R₀| is up to 21 % at the resin pocket of carbon fiber woven composites. However，|R₀| is dependent on the wavelength and resin-thickness between neighboring interlaminar stacks at interlaminar interface. The 3D microstucture of woven composites was well visualized by using ultrasonic B-scan and T-scan imaging techniques，based on the sonic information resulting from reflections at the resin pocket，fiber bundle and interlaminar interface. The experimental results show that the orientation，shape，distribution and size of the resin pockets，woven fiber bundles and their topologies as well as lay-up of woven laminate can be seen well by employing the ultrasonic imaging technique with high-resolution. It provides an effective instrument for characterization of bulk microstructures and evaluation of micro-defects in woven composites.