Intrusive laser triangulation method for non-contact detection of voids in translucent composites

• Published in: NDT & E international : independent nondestructive testing and evaluation 2024-07, Vol.145, p.103143, Article 103143
• Main Authors: Bračun, Drago, Selak, Luka, Klobčar, Damjan, Katić, Marko, Markučič, Damir
• Format: Article
• Language: English
• Subjects: Defects; Laser triangulation; Non-destructive testing; Optical properties; Resin transfer moulding
• ISSN: 0963-8695; 1879-1174
• DOI: 10.1016/j.ndteint.2024.103143

A non-contact optical inspection method for detecting voids in translucent composites is presented. Structured laser light is used to illuminate the inspected part. As the light penetrates the matrix, it scatters and is reflected from internal structures, rendering them perceptible in close proximity of the laser illumination. A systematic image acquisition and scanning approach is employed along with image processing to reconstruct and visually represent the internal composition of the inspected part. Experiments involving translucent epoxy and polyester based composites demonstrate capability to detect voids with depths reaching up to 5 mm. The detection depth is predominantly influenced by the light transmittance properties of the matrix, as well as the density and quantity of fiber layers. The arrangement of the camera and laser on the same side of the inspected part facilitates the examination of parts with varying thicknesses. The presented method is intended for automated inspection in mass production by leveraging its non-contact characteristics and high operational velocity. •Voids are visible in close proximity to structured light illumination.•Void detection up to a depth of 5 mm, influenced by resin transparency and fiber density.•Independence of variations in part thickness.•Enables high-speed automated inspection in mass production.