Getting light through cementitious composites with in situ triboluminescent damage sensor

Triboluminescent damage sensors comprising highly efficient triboluminescent materials could allow simple, real-time monitoring of both the magnitude and location of damage. The inability to effectively capture and transmit the triboluminescent optical signals generated within opaque composites like concrete has, however, limited their damage monitoring applications. The in situ triboluminescent optical fiber sensor has been developed to enable the detection and transmission of damage-provoked triboluminescent emissions without having to position triboluminescent crystals in the host material. Flexural tests were performed on mortar and reinforced concrete beams having the in situ triboluminescent optical fiber sensor integrated into them. The intrinsic triboluminescent signals generated in the beams under loading were successfully transmitted through the optical fibers to the photomultiplier tube by side coupling. Successful side coupling will make a truly distributed in situ triboluminescent optical fiber sensor possible when the entire length of the sensor is mostly covered with the triboluminescent composite coating. The results show the viability of the in situ triboluminescent optical fiber sensor for the structural health monitoring of cementitious composites. Real-time failure detection was demonstrated in unreinforced mortar beams, while real-time damage (crack) detection was demonstrated in reinforced concrete beams. Preliminary work on reinforced concrete beams showed that the integrated in situ triboluminescent optical fiber sensor was able to detect multiple cracks caused by loading, thereby providing early warning of structural degradation before failure.