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Figure: Side assembly bogie side frame undergoing testing, showing wiring to fiber optic sensors.
For fiber composites to be used with confidence in primary load bearing structures, methods of monitoring strains in service use are essential. The partners in the Eureka 1841 Eurobogie project used FBGS fiber optic sensors (Draw Tower Gratings) to monitor strains of components moulded using different methods.
The potential of fiber optic sensors to monitor strains and delamination cracks, especially in thick fiber-reinforced composites was investigated. High strain optical fibers have been moulded within 10 mm of the tensile surface.
Within the whole experimental programme, the beams have been loaded in 3 point bending to loads up to 160 kN and strains of 1.5%. The immediate observation is that the moulding, curing or post curing does not affect the condition of the optical fibers nor do the fibers affect the strength of the beams. Furthermore, a good correlation between the output of the mechanical gauges bonded to the tensile face and the fiber optic sensors could be observed during loading.