Next Generation Acoustography Ultrasonic NDI for Advanced Composite Materials and Structures

摘要

Acoustography differs from conventional ultrasonic testing in that test objects are inspected in full field, analogously to real time x-ray imaging. The approach uses a novel, super high resolution large area acousto-optic (AO) sensor, which allows image formation through simple ultrasound shadow casting, analogous to x-ray image formation. Recent improvements in AO sensor technology have greatly expanded acoustography s nondestructive inspection (NDI) abilities. These recent developments offers significant advantages over conventional point-by-point ultrasonic scanning methods, such as wide area inspection, high resolution, circumvention of bulky mechanical scanning apparatuses, very user friendly allowing use and interpretation of data by low skill level operators and simple set-up, thus making acoustography very efficient and a powerful inspection tool during manufacturing. In addition, acoustography is also being developed so that it can be adapted for field inspection use. Composite materials are widely used in aerospace structures for their exceptionally high specific strength to weight ratios. Acoustography was used to inspect a variety of impact damaged carbon/epoxy composite coupon samples, typically used in aerospace structures. In addition, US Army helicopter main rotor blade sections with induced field damage were also inspected. These structures include a variety of materials, such as a primary metal inner load carrying beam structure (spar), a Nomex honeycomb core region sandwiched between thin glass/epoxy skins and all components adhesively bonded. Induced damage to the blade sections simulated typical field threats, such as, low velocity ballistic impacts from projectiles, fragments or debris, as well as, simulated maintenance tool drops causing localized crush core damage to the honeycomb region. Acoustography inspection results will be presented side-by-side with conventional ultrasonic inspection results.