Distributed strain measurement using fibre optics in a high performance composite hydrofoil

With rapidly advancing composite manufacturing industry in recent years, advanced composites have become favourable alternative materials to conventional alloys in marine propeller production. However, composite structures are very susceptible to failure and thus strain monitoring in multiple locations throughout the structure will be essential to prevent catastrophic failure. In this experiment, composite hydrofoil was manufactured using resin transfer moulding (RTM) and embedded with a standard single mode optical fibre along the trailing and leading edges for distributed strain sensing. Distributed sensing with continuous fibre can be implemented in complex composite structures such as a high performance composite hydrofoil or propeller for structural monitoring purposes. Quasi-static loads were applied to the instrumented composite hydrofoil achieving deflections of up to 11 mm to monitor strains in multiple locations through distributed fibre sensing using a high sensitivity optical backscatter reflectometer (OBR). The strain field within the layered hydrofoil was produced, and the experimental result was validated using finite element analysis. The combined numerical and experimental validation demonstrates that fibre optic distributed sensing is reliable and can be utilised for structural health monitoring of high performance composite hydrofoils.