Search

This paper presents an investigation into structural performance of a shape adaptable composite hydrofoil which was manufactured using Automated Fibre Placement (AFP). The methodology and procedure developed for the complex manufacture using AFP is first described here. A mould originally designed for resin transfer moulding (RTM) was used as a tooling surface for AFP layup. An in-house developed optimisation process for tailored bend-twist behaviour was used to obtain the layup sequence and subsequent tool path creation for AFP fabrication of the hydrofoil. The AFP fabricated hydrofoil was experimentally tested for its structural response using a static cantilever experiment whereas for the dynamic behaviour experimental modal analysis (EMA) was used. Finally, a comparison was made between the structural responses of the optimised hydrofoils manufactured by AFP and using the traditional RTM process.

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.

The propulsive efficiency of a shape adaptive composite propeller increases with passive pitch (twist) change under a hydrodynamic load. These adaptive marine propellers are usually designed using straight fibre tows to obtain optimised layup with such bend-twist character. This paper aims to present an alternative optimisation approach for such composite propellers using a curved fibre path method where tow paths are allowed to vary spatially within individual plies. In this work, three optimisation studies were performed to highlight that employing curved tows produce better results, including increased twist change for efficiency or, lowered deflection for structural improvements. Laminate plates were first optimised and manufactured using an automated fibre placement robot for experimental validation. Cantilevered loading test results show that optimised curved fibre plates generated >10% more twist compared to their straight fibre counterparts. In the following optimisation on a hydrofoil model, the curved fibre design produced the same tip angle change as the optimised straight fibre layup, yet it reduced the tip deflection by 15%. Finally, the optimisation was performed on a Wageningen B-series marine propeller, in which the optimised blade design with curved fibre layup achieved a 20% reduction in the Tsai-Hill failure index under the same pitch change.