Comparison of fixture-based and manual fiber integration in adhesive joints: Effects on strain signal quality

Fiber optic sensors (FOS) offer great potential for monitoring the stress state within an adhesively bonded joint making them suitable for in-situ structural health monitoring of critical bonds. Thus, FOS are used to measure the strain or temperature at any given location along the fiber length by correlating the change of these state variables to a shift in the Rayleigh backscattering. However, there are some hurdles to consider when incorporating FOS for the monitoring of structural bonds. Given that the local strain state within the adhesive layer is contingent on the applied stresses and, consequently, the position of the FOS within the adhesive layer, the repeatable positioning of the FOS in the adhesive layer is imperative. The present study methodically compares two approaches for the integration of FOS within the adhesive layer of tensile shear specimens, comprising a single layer, with the objective of evaluating them based on the resultant fiber orientation and signal quality of strain measurements.