There is a growing interest in the use of fibre reinforced plastics (FRPs) as high-grade construction material for variouw applications that need to be lightweight, yet strong in sometimes harsh loading conditions. Despite the growing popularity of structural composite materials, one has to realize that their mechanical behaviour is significantly different compared to conventional isotropic construction materials. Strain monitoring of an in-service structure should greatly enhance the insight and confidence in the (long-term) behaviour of high performance composite structures.
Structural health monitoring necessitates the possibility of measuring multi-axials strain fields. High birefringent optical fibres (HiBi-fibres) with Bragg grating can become a solution in this matter. Designing a multi-axial strain sensor based on optical FBGs should meet several basic requirements which are discussed in this dissertation
