An Integrated Fiber Optic Based SHM System for Structural Composite Components: Application to a Racing Motorbike Fork

The aim is to create a smart structure holding the benefits of a structural monitoring system combined with the high performance of composite materials in a key component of a racing motorcycle, that is the front fork. Telescopic forks in composite material allow mass reduction while maintaining adequate stiffness, even if their use is currently limited only to a niche of applications, mainly for wear issues. Here, the fork tube was designed, optimizing the lamination sequence to replicate the stiffness of the original fork. The applied monitoring system uses optical fibers, for which composites are an excellent host material, with Bragg grating sensors. From the deformations measured is possible to derive information on the integrity, to set the performance of stiffness and to detect the loads. Given the difficulties in the correct positioning of the sensors (diametrically opposite on a cylindrical surface) and to imagine an effective use during racing, the need was highlighted to implement a system allowing a safe, easy, and precise positioning of the optical fiber on a predetermined path between the composite layers and the proper housing of the relative connector. The fork tube equipped with the smart veil was made by autoclave forming and then tested in the laboratory both alone and mounted on the bike. The result is a component whose deformations are known in real time, that integrates adequately protected and well-placed sensors, that are linked to the acquisition by means of a connector embedded directly into the structure itself.