Compton Scattering Three-dimensional Imaging System for in situ Nondestructive Inspection of Large Honeycomb Sandwich Structures

ABSTRACT: To address the Air Force need for a reliable method to inspect large aircraft honeycomb sandwich structures, Physical Optics Corporation (POC) is continuing the development of a new automatic, three-dimensional (3D) Compton scattering IMaging system for in situ nondestructive inspection (NDI) of large HOneycomb Sandwich structures (IMHOS), providing accurate detection and identification, and precise 3D localization/measurement of possible disbonds, core and skin defects, and fluid intrusions. The IMHOS is based on a POC-developed high-contrast Compton imaging tomography technique, optimized for NDI of these structures, and POC-patented X-ray imaging optics. The IMHOS is a low-dose, in-field, noncontact system requiring access to structures for inspection from only one side. In Phase I, POC successfully demonstrated the feasibility of IMHOS in experiments using the benchtop prototype in POC"s X-ray lab, on honeycomb sandwich samples with imitation defects, disbonds, and liquid intrusions. In Phase II, POC will develop and test a fully functional (TRL-6) IMHOS system, demonstrating accurate detection, precise spatial localization, and measurements of disbonds and different skin and core defects of large metal and nonmetal honeycomb sandwich structures of varied geometric forms; detection of liquid intrusions; and differentiation of the type of liquid (fresh and salt water, oil, other organic liquids). BENEFIT: Military applications of the IMHOS system will include in situ in-field automatic NDI of large aircraft honeycomb sandwich structures for accurate identification, localization, and measurements of disbonds, skin and core defects, and liquid intrusions, including identification of the detected liquid (e.g., fresh and salt water, oil) during aircraft depot maintenance, or in-field. The IMHOS system can be incorporated by the U.S. Air Force, Navy, and Army and for reliable, rapid, automatic, easy-to-use NDI of large honeycomb sandwich structures used in aircraft and other military platforms. With minor modification, the IMHOS system can also be used for NDI of parts containing light, heterogeneous, materials (e.g., explosives, adhesives, electronic components, composites, plastics). An expansion of most of the techniques developed under IMHOS in Phase II can transition to commercial applications for NDI of large honeycomb sandwich structures, and also multilayer aluminum/composite structures with complex geometries in civilian aircraft, spacecraft, light vessels, etc. With further minor modifications, the IMHOS system can also be used for detection of hidden objects inside airframe cavities in fuselages, wings, etc.