Use of a Tailor-Made Fiber-Bragg-Grating Patch for Separation of Superimposing Load Cases in a Filament-Wound Composite-Drill Tube

In many structural components, a major interest lies on the monitoring of the exact condition of a component or the loads acting on it for which sensors are an important tool. The usage of fiber-Bragg-grating (FBG) sensors has many advantages considering sensor embedment and strain measurement in fiber reinforced composites. However, the direct calculation of applied loads based on the measured strain is impeded when FBG sensors are integrated conventionally, mainly due to parasitic effects from the cross coupling of axial and torsional strains. The presented work introduces an FBG patch produced in tailored fiber placement. A calculation approach is presented, which allows the calculation of superimposed loads from the FBG-strain while compensating for temperature and cross coupling effects. Experimental data from the use case of boring & trepanning association (BTA) deep hole drilling are presented to verify the calculation approach for the sensor patch and show vastly improved measurement accuracy compared to the conventional FBG integration.