Laser ultrasound inspection system

As Lockheed Martin (Ft. Worth, Texas) developed carbon fiber composite structures for the F-35 Lightning II Joint Strike Fighter earlier this decade, the company identified the necessity of high-speed composites inspection and developed its own system based on laser ultrasound technology. That technology was eventually sold to a third party, but the engineers who developed it went their own way and in 2008 founded iPhoton Solutions LLC (Ft. Worth, Texas), which recently introduced its first composites inspection system based on laser ultrasound technology. The system, called iPLUS, is a conventional laser-ultrasonic technology for the inspection of polymer-matrix composites. It uses a short-pulse CO2 laser to generate ultrasound by thermal expansion in the composite. A second laser coupled to an interferometer detects the resulting ultrasonic signals. The composite part is the source of the ultrasonic wave, therefore, with angles of incidence as high as 45°, the ultrasonic wave is launched inside the composite normal to the part surface. The ensuing ultrasonic signals are interpreted like those obtained using conventional piezoelectric transducers. The system is integrated with standard articulated industrial robots, allowing for its use in a variety of applications, including inspection of fuselages, stringers and tight-radius parts. The iPLUS system has inspected structures up to 43 mm/1.7 inches thick and can automatically scan up to 64 ft²/hr (6 m²/hr). Once a composite structure is in a fixed location, the iPLUS system automatically scans from a distance of about 72 inches/1,829 mm, checking for delaminations, inclusions and porosity. Results are presented for A scan and C scan, like pulse echo ultrasound systems. The system is designed for production inspection, with in-service inspection an eventual possibility.