Smart monitoring of a full-scale composite hydrofoil manufactured using automated fibre placement under high cycle fatigue

Abstract

Fibre reinforced composites materials offer a pathway to produce passive shape adaptive smart marine propellers, which have improved performance characteristics over traditional metallic alloys. Automated fibre placement (AFP) technology can provide a leap forward in cyber-physical automated manufacturing, which is essential for the implementation and operation of smart factories in the marine propeller industry towards Industry 4.0 readiness. In this paper, a comprehensive structural health monitoring routine was performed on an AFP full-scale composite hydrofoil to gain confidence in its dynamic and structural performances through a number of active and passive sensors. The hydrofoil was subjected to constant amplitude flexural fatigue loading in a purpose-built test rig for 105 cycles. The hydrofoil was embedded with distributed optical fibre sensors, traditional electrical strain gauges and linear variable displacement transducers. Both microelectromechanical system and piezoelectric accelerometers were used to conduct experimental modal analyses to observe changes in the modal response of the hydrofoil at regular intervals throughout the fatigue program. The hydrofoils modal response, as well as the stiffness measured using both displacements and strains, remained unchanged over the fatigue loading regime demonstrating the structural integrity of the hydrofoil. The optical fibre sensors endured the fatigue test cycles showing their robustness under fatigue loads. Furthermore, the sensing systems demonstrated the potential of being utilised as a useful maintenance tool combining their adaptability with automated manufacturing during manufacturing through integration within the hydrofoil, a structural test framework for performance measurement, data acquisition and analytics for visualisation, and the prospect of decision making for maintenance requirement during any onset in structural performance.

Acoustic emission monitoring of composite marine propellers in submerged conditions using embedded piezoelectric sensors

“…It was noted that the measured strains were in reasonable accordance with simulations. This research was continued by Shamsuddoha et al [8] who embedded distributed optical fibres into a full-scale composite hydrofoil loaded under fatigue. In that work, also piezoelectric accelerometers were placed to perform modal analysis.…”

“…This matters as unanticipated failure of a propeller blade will considerably limit a vessel's manoeuvrability. Prominent causes to the uncertainty are deviations and imperfections during fabrication, the varying loading of the blade, and a complex internal stress state imposed by the thick intricate geometry and spatially-varying material layup [8,9]. Additionally, depending on their location and load history, different damage types may grow to gross failure or cause a stress redistribution that leads to different failure [10].…”