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This recommended practice establishes generic reference standards that will accommodate nondestructive inspections (NDI) on a broad range of non-metallic composite honeycomb structures found on aircraft.

The purpose of this Aerospace Recommended Practice (ARP) is to describe the design and production of composite honeycomb calibration standards to be used in ultrasonic, resonant, and tap test NDI equipment calibration for accomplishment of damage assessment and post-repair inspection of aircraft composites. These standards may also be appropriate for other NDT methods but will need to be assessed as appropriate prior to their use. The standards are representative of damage found in the field and include typical flaw scenarios such as disbonds and delaminations. It is intended that these standards be adopted by aircraft Original Equipment Manufacturers within procedures contained contained in their Nondestructive Testing Manuals. Depending on the nature of the inspection, it may be necessary to compensate for variations in material properties through the use of correction factors or by adjusting for these differences on the part or structure being inspected. In certain instances, it may be desirable or necessary to design a new reference standard to accommodate a specific inspection application.

Currently, the recognized number of composite honeycomb construction variables makes the resulting number of specimens very large and unmanageable. Inspection characterizations and equipment responses have been used to determine the important variables needed in a composite reference standard thus eliminating unnecessary standard configurations. This ARP describes a workable number of reference specimens that can meet the needs of a broad range of honeycomb structures found on aircraft.