In situ strain and temperature monitoring of adaptive composite materials

Abstract

An optical fiber sensor is designed to simultaneously measure strain and temperature in an adaptive composite material. The sensor is formed by splicing two fiber Bragg gratings (FBGs) close to each other, which are written in optical fibers with different core dopants and concentrations. Their temperature sensitivities are hence different. The sensor is tested on an adaptive composite laminate made of unidirectional Kevlar-epoxy prepreg plies. Several 150 mu m diameter prestrained NiTiCu shape memory alloy (SMA) wires are embedded in the composite laminate together with one fiber sensor. Simultaneous monitoring of strain and temperature during the curing process and activation in an oven is demonstrated.