This Small Business Innovation Research Phase I project will develop a new approach to detection and classification of damage to a structural composite part, thus providing a means for sensing structural degradation such as delaminations, fatigue and other damage. Piezoelectric transducer technology provides a means for sensing various structural properties such as stress, strain, and elasticity when these sensors are mounted on, or embedded within, a material structure. Structures may degrade due to improper manufacture, duty cycle wear, impacts, and material corrosion. Embedded sensors may be used to signal changes, likely to be damage, to a structural composite part and permit off-line diagnosis independent of the long-range geometry of the part, so that the diagnostic instrument need not have records for individual parts. This project uses high-frequency acoustic signals to diagnose damage, calibrating for local properties (density, thickness, stiffness). Standard acoustic test pulses from the piezoelectric devices can be used to probe for damage located between pulse generators and sensors. By using only the leading portion of the received signal it is possible to avoid the effects of geometry-dependent reverberation. This greatly simplifies the interpretation of changes in the response as clues to structural degradation. The advanced structural monitoring concepts being sought have potential of commercial use in the civil transportation industry for aircraft, automobiles, trucks and boats, and in the commercial space industry for boosters and satellites. Other application areas include the use of structural composites in load-bearing bridges, composite railroad cars, and numerous other areas where light-weight high-strength structural composites are replacing heavy metallic structures.
