Invention of Metal-Based Smart Composites with Embedded Optical Fiber to Obtain a Function of Self-Monitoring

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Metal-based smart composites with embedded fiber optic sensor were tried be fabricated to enable their self-monitoring. Aluminum and epoxy resin were used as matrices, and quartz-type single-mode optical fiber was used to form sensors in them. Asanuma developed a simple and low cost method to form sensitive fiber optic sensors in matrix materials. It can be explained as follows : A notch or multiple notches are made on optical fiber and it is embedded in a matrix. Then, it is tensile tested to break the fiber at the notches to form optical interference sensors. As they are made in the matrix, alignment of optical axes and encapsulation are not necessary.A transparent epoxy matrix specimen with one notch was tensile tested under monitoring optical transmission. When the embedded fiber fractured, visible laser leaked from the fractured part and optical intereference was observed during tensile test, which means that an interference type sensor was successfully formed.Optical loss type sensor was also tried to be made by making multiple notches. Effect of their spacing on fracture was investigated using epoxy matrix and it was clarified that the spacing has to be equal to or larger than 4mm. To decrease it and increase density or sensors, bending was more effective than tension. Pre-notched optical fiber could also be embedded in aluminum matrix without fracture by the interphase forming/bonding method which was developed by Asanuma, and similar results were successfully obtained In order to use this type of sensor for self-deformation monitoring of a CFRP/aluminum active laminate, 15 notches of 3mm spacings were formed in it. As the optical loss almost monotonically increased with increasing curvature of the laminate by its thermal deformation, the array of sensors proved to be effective for its defromation monitoring.