Experiences from ultrasound testing - Olympus Omniscan MX and DolphiCam CF08/DF16

Modern military platforms, such as the NH90 helicopter and the F-35 Joint Strike Fighter, consist of a large percentage of light-weight materials, such as composites. New materials require new and different techniques for efficient and reliable inspection to detect damages that may be critical for the performance and safety of the platform. This is particularly relevant for helicopters/aircrafts, but also for land vehicles and ships. Non-destructive inspection methods are defined and employed as part of the maintenance system for modern composite structures, but more research and testing is required. FFI supports the Norwegian Armed forces and the Norwegian Defence Logistics Organization (NDLO) in this work. This study was performed to compare and contrast two different types of ultrasonic nondestructive inspection (NDI) systems, while investigating simulated damages in carbon fibre reinforced polymer (CFRP) panels and repairs in a sandwich panel. The ultrasound systems investigated in this study were the Olympus Omniscan MX, a common phased-array unit, and two models of the DolphiTech DolphiCam™, which is a relatively new matrix-array system for area scan. Four CFRP panels were produced with simulated delaminations consisting of Teflon® and aluminium inclusions, blind drill holes, and impact damages. A glass fibre/Nomex honeycomb sandwich panel with scarf repairs was also investigated. In total, there were over 70 different types and depths of damage investigated by the NDI systems. Ultrasound imagery of the simulated damages provided information on the accuracy, applicability, and relative strengths and weaknesses of the two systems. The DolphiTech cameras, consisting of two models designed for 8 mm and 16 mm thick CFRP structures, DolphiCam™ CF08 and DolphiCam™ CF16, respectively, provided very detailed imagery and depth measurements of all types of simulated damages. Defect features of less than 1.0 mm out of plane could easily be detected and measured. Further, the DolpiTech cameras required minimal set-up time, and performed well in both freezing and controlled room temperature environments. The Olympus Omniscan MX system, requiring a longer set-up time and having larger support equipment requirements, was also able to detect the simulated damage areas. Finally, the Olympus Omniscan MX system performed quicker inspections of much larger areas compared to the DolphiTech cameras. This study found that the two types of NDI systems offered complementary strengths and weaknesses when employed for detection of simulated damages in CFRP materials. Also, DolphiCam™ CF08 showed surprisingly good results at investigating bonded scarf repairs to the glass fibre/Nomex sandwich panel.