Embedding microstructured optical fibres in complex aerospace-grade components: from mechanical validation to multi-axial strain sensing

Embedded optical fibre sensors (OFS) offer promising structural health monitoring capabilities for aerospace composites, but each sensor–material–process combination requires independent validation. This study presents the first comprehensive demonstration of embedding microstructured optical fibre Bragg grating-based (MOFBG) sensors into aerospace-grade composites manufactured via liquid resin infusion (LRI) and resin transfer moulding. We combine sensor survivability analysis, standardised mechanical testing, and successful integration in a geometrically complex, load-bearing subcomponent. The sensors enabled robust in-situ cure monitoring and multi-axial strain sensing, with 100% survivability in LRI composites. Mechanical testing revealed no significant structural degradation when the OFS were embedded. These results advance the technology readiness level (TRL) of embedded microstructured OFS from laboratory-scale validation (TRL 4) towards demonstration under aerospace-representative conditions (TRL 6). To our knowledge, this is the first study to validate MOFBG performance in both controlled test coupons and realistic 3D composite geometries, marking a key step toward certified structural health monitoring in advanced composite structures.