Pultruded fibre reinforced polymer reinforcements with embedded fibre optic sensors

Abstract

The use of the pultrusion process for the manufacture of fibre reinforced polymer (FRP) composites with embedded fibre optic sensors is discussed. The specific application is the use of smart composite reinforcements for strain monitoring in innovative concrete bridges and structures. The Bragg grating and Fabry-Perot fibre optic sensors are embedded during the pultrusion of FRP rods and the process-induced residual strains are evaluated using these sensors. The behaviour of optic sensors during pultrusion is assessed, and the effect of the embeddment of optical fibres and their surface coatings on the mechanical properties of the composite material is investigated. To verify the operation of the optic sensors embedded in the smart pultruded rods, mechanical tests were conducted and the output of the fibre optic sensors was compared to that of an extensometer. These mechanical tests were performed at room temperature as well as under conditions of low and high temperature extremes. The reliability assessment of the fibre optic sensors further entailed the study of their fatigue and creep behaviour as well as their performance when the rods in which they are embedded are placed in a severe environment (e.g., alkaline solutions) that may simulate conditions encountered in concrete structures wherein the composite rods will be used as prestressing tendons or rebars.