Multi-axial strain transfer from laminated CFRP composites to embedded Bragg sensor: II.Experimental validation

Abstract

Embedded optical fibre sensors are considered in numerous applications for structuralhealth monitoring purposes. Since the optical fibre and the host material in which it isembedded have different material properties, the strain in both materials will not be equalwhen external load is applied. Therefore, the strain transfer from the host material to theembedded sensor (optical fibre) was studied in more detail in the first part of the paper.This second part presents an experimental evaluation of the response of uni-axial fibreBragg grating sensors embedded in small cross-ply composite laminates subjectedto out-of-plane transverse loading. This loading case induces high birefringenceeffects in the core of the optical fibre. Using the numerically determined straintransfer coefficients (Luyckx et al 2010 Smart. Mater. Struct. 19 105017) together withmulti-axial strain formulations, the authors were able to measure with reasonableaccuracy the total strain field inside a carbon fibre reinforced plastic specimen.