EMBEDDED EXTRINSIC FABRY-PEROT FIBER OPTIC STRAIN ROSETTE SENSORS

The ability to determine the state of strain within a plane is of great importance to the health monitoring of composite materials and structures. In this preliminary study, fiber optic strain sensors are arranged in a rosette configuration to study their effectiveness in monitoring arbitrary strain states within a neat resin and a graphite/epoxy laminate. The extrinsic Fabry Perot Fiber Optic Strain Rosette Sensor (FP-FOSRS) is very capable of measuring axial (0-degrees) and transverse (90-degrees) strains. However, discrepancies are noted between strain measured by the embedded Fabry Perot Sensors and externally mounted strain gages at 45-degrees. Further, it is believed that the compressive strength of FP-FOSRS embedded composites is most affected by the sensors' presence. A compressive strength reduction of 300% is measured. This reduction is compared with the result predicted by a micromechanical model.