Development of a portable mechanical hysteresis measurement and imaging system for impact characterization in honeycomb sandwich structures

Honeycomb sandwich materials are commonly used for aero‐structures, but because the outer skins are typically thin, 2–10 plys, the structures are susceptible to impact damage. NDI methods such as tap tests, bond testers and TTU ultrasound are successfully deployed to find impact damage, but identifying the type∕degree of damage is troublesome. As the type∕degree of impact damage guides decisions by the maintenance, repair and overhaul (MRO) community regarding repair, the ability to characterize impacts is of interest. Previous work demonstrated that additional impact characterization may be gleaned from hysteresis loop area, as determined from an out‐of‐plane load‐vs‐displacement plot, where this parameter shows a correlation with impact energy. This presentation reports on current work involving the development of a portable hysteresis measurement and imaging system based on an instrumented tapper. Data processing and analysis methods that allow production of the load∕displacement data from a single accelerometer are discussed, with additional reporting of tests of software to automatically vary pixel size during scanning to decrease C‐scans inspection time