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Optimization of fiber Bragg sensor configurations for in situ failure identification in woven composites throughout impact

In this study, the development and optimization of embedded fiber Bragg grating (FBG) sensor networks within composite materials was investigated. Various densities of optical fibers were embedded within composite laminates, and low-velocity impact damage responses were evaluated to determine the effects on the mechanical behavior of the laminates. The woven composites were subjected to multiple strikes at 2 m/s until perforation occurred, and the impactor position and acceleration were monitored throughout each event. From these measurements, we obtained dissipated energies and contact forces for specimens with and without embedded optical fibers. Embedded fibers were interrogated with light to determine the degree to which light could pass through them for each density and arrangement. Cross sectional optical micrographs of the specimens were used to determine the local effects of the embedded fibers on neighboring fibers and the surrounding matrix material, both before and after impact events. Currently FBG sensors are being calibrated and prepared for embedment in specifically chosen configurations within the composite. They will be serially multiplexed together to create a single fiber sensing network capable of monitoring damage over a large area. Real time strain information will be gathered as future embedded laminates are subjected to impact events, and the resulting data will be used to better monitor and predict damage in the composite system.