A Novel Non-Contacting Strain Measurement Method for Nondestructive Inspection and Health Monitoring of Carbon Composites

"Carbon composite structures are critical to BMDO's missions. A structural failurehas very expensive consequences and might affect our Nation's safety. Existingnondestructive inspection methods have a variety of drawbacks, and therefore the useof composites proceeds with both caution (e.g., overdesign, premature retirement ofcritical structures) and risk.Quantum Magnetics, Inc., is proposing a novel strain gauge that shows excellentpromise for advancing nondestructive inspection and health monitoring of carboncomposite structures. The proposed non-contact and non-intrusive method is based onQuadrupole Resonance (QR) and does not require an external load. A small percentageof a tiny and inert crystalline additive is either applied as a thin additive/resincoating on the structure's surface or embedded in the composite structure during itsmanufacture. A portable detector head transmits brief, non-harmful radio frequencypulses and detects the additive's strain dependent response. Maps of internal andsurface strains will be helpful to make an informed decision on whether the structureis safe for use or whether repair/ retirement is needed. In Phase I we will studythe feasibility of both QR based approaches in carbon composites, and in Phase II wewill demonstrate detection of different types of flaws including fatigue-inducedflaws. The proposed technology will significantly advance nondestructive evaluation andhealth monitoring of c