Differential Nonlinear Elastography for Characterizing Bond Strength

"Quantitative nondestructive evaluation (NDE) of adhesively bonded joints has been an elusive goal for decades. In this Phase I SBIR effort, Nascent will explore the development of Differential Nonlinear Elastography (DNE), linking quantitative physicalmeasurements to practical engineering properties. The only way to fully characterize bond strength today is to fail the bond. Inspection limitations coupled with fault tolerant design philosophy often require mechanical fasteners, adding weight and mayactually weaken the structure and introduce paths for water intrusion. Because of these limitations, advanced structures are currently unable take full advantage of adhesive bonding. This proposal brings a robust area of physics to focus on this problem,building on advances from both medical and geophysical systems. DNE will topographically assess higher-order elastic properties that are missed by conventional ultrasonic measurements. These properties are directly tied to the local state of the materialand are especially influenced by strain. DNE creates a differential strain state that is used to assess the strength of the insonified bond. The work will progress along two paths: the first to quickly verify aspects of the concept, the second leading toa fieldable instrument. Success in these efforts would represent a genuine breakthrough in quantitative NDE. The successful development of Differential Nonlinear Elastography (DNE) w