Develop a Tool to Measure Bonded Joint Strength for Primary Load Bearing Aircraft Structures

This is a proposal to develop the technology to detect “kissing bonds” (adhesion bonds that are not broken but are well below design strength). The approach is to use a novel ultrasonic transducer that is capable of generating pulse amplitudes that produce strains just below the required bond strength. If the bond survives the pulse it is considered good. Previous work has shown the feasibility of this approach. The new approach sends an extended signal from a piezoelectric into a “broadband resonator”. By selecting the correct input signal all frequency components arrive at the output in phase at some later time to produce a pulse of the required amplitude to break kissing bonds. A portable, battery powered system could be developed to handle a wide range of material thickness with hand-held transducers spanning a broad range of center frequencies. The experimental plan is to fabricate specimens containing bonds of various strengths, subject the bonds to pulses just below the bond strength, note any failures, and then test the strength of any intact specimens with destructive tests.