A Portable Impactor Device

The NASA impactor is a fully portable device that propels an instrumented projectile so that it impacts a vehicle, structural component, or test specimen. The device includes a projectile inside an exterior tube. The projectile itself contains a commercial load cell designed to obtain the dynamic force response during the impact event. Furthermore, a digital oscilloscope and optical sensor are combined to measure the velocity just prior to impact so that the impact energy of the projectile onto the test surface can be calculated. In the current configuration, impacts with energies between 4 and 40 J (between about 3 and 30 ft-lbs) are obtainable, and could be adjusted by changing the spring to one with a different spring constant. The tube can be handheld or rigidly mounted at any angle such that the impact response can be evaluated at specified positions throughout the test article. The impactor device is primarily designed for use on composite structures to investigate the structural response from a low-velocity impact, as composite materials are highly susceptible to damage from low-velocity impacts where the damage may not be visible but results in great loss of strength. If the damage cannot be detected visually, it can be seen through nondestructive testing (ultrasonic, flash thermography or X-ray). However, the device may also be used on structures to evaluate and tune structural health monitoring systems. The technology has been designed, prototyped, and implemented in four military or government programs for impact testing on metallic and composite structures, including a helicopter roof in 2013. The cost of the parts for the prototype was approximately $9,000. Production costs are expected to be lower.