Evaluating Strain Limits of Embedded FBG Sensors in Pultruded Hybrid Composite Rods

This paper demonstrates that relatively inexpensive acrylate coated FBGs can survive short exposure times to high temperatures in a pultrusion process and monitor relatively low magnitude bending and axial tension strains in a composite material. However, under higher sustained axial loads, the observed interfacial failure of the optical fiber and the host material resulted in a significant reduction of the indicated strains during constant elongation. These findings are analyzed by experimental measurements supported by finite element simulations. The optimal placement of embedded optical fibers in the rods is discussed based on the limitations of the rods and the mechanical strength of the commercially available optical fibers.