Materials Science

A Light Approach to Failure

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Science  11 May 2001:
Vol. 292, Issue 5519, pp. 1023
DOI: 10.1126/science.292.5519.1023c

Certain crystalline materials (including table sugar) emit light when then are fractured. This property, triboluminescence, can be exploited to make sensors to detect structural damage, such as in composite materials, where internal damage is often not accompanied by external indications of failure. One factor that has limited the use of these systems is getting the light from the fracture source to a detector. The light may have to travel relatively long distances (as in the case of an aircraft component) or through strongly absorbing materials (as in the case of a carbon fiber-reinforced plastic). In a typical setup, the triboluminescent material is coupled to a silica optical fiber that is used to transmit the emission, but the signal-to-noise (S/N) ratio for this system is poor. Sage et al. have designed two systems, one polymeric and one silica based, in which the sensor material is coupled to a photoluminescent fiber that captures the initial emission and then reemits at a frequency that matches the waveguide modes of the fiber. For these new detectors, a significantly improved S/N ratio was observed, and for glass fiber composites, the detectors acted as global sensors—only a few detectors were needed to detect damage throughout the entire specimen. — MSL

Smart Mater. Struct.10, 332 (2001).

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