Automated Manufacture of a Shape-Adaptive Large Hydrofoil

Abstract

In the past decades the usage of composite as material construction for marine applications had increased exponentially. Special devices like rudders, hydrofoils and propeller blades have been investigated worldwide and proved to be more efficient if some flexibility can be achieved (Young et al. (2016), Wu et al. (2015), Zarruk et al. (2014) and Ducoin et al. (2012),). The most common material used in this task is carbon reinforcement plastic (CRP). One remarkable advantage of using CRP as construction material is the high corrosion resistance in marine environment. But the main reason why CRP propeller blades and hydrofoils are gaining popularity is due to the bend/twist capability that allows them to adapt the pitch when working under different loading conditions. This pitch adaptive capability can increase the efficiency of the propeller and hydrofoils when it works in out of the design conditions as mentioned in Herath et al. (2013). The bend/twist capability under hydrodynamic loads is normally called hydroelastic tailoring. This is a passive capability does not need additional mechanism to work as in the case of controllable pitch propellers, decreasing significantly the acquisition cost. With the potential use of composite materials to create high efficiency structures in different fields of engineering, many automated techniques have been developed in the last decades. One of the most used is the Automated Fibre Placement (AFP). Specially used in aerospace applications due to the high-quality control during the manufacture and capability to elaborate large scale parts. AFP is and advance manufacture technique for composite materials which could work with thermoset and thermoplastic materials. This technique consists in a robot head that place tows or tapes in a prefabricate mould in a desire orientation, covering the required surface. The robot head has a heating torch that pre-cure the tape for the case of thermoset materials. Since the procedure fully automated, it is possible to manufacture complex geometries and work with precise orientations of the fibres without difficulties. One of the main advantages of this manufacture process is the low level of voids and imperfections inside the lamination compared to the traditional manufacture techniques as Resin Transfer Moulding (RTM), Vacuum Assisted Resin Infusion (VARI) or manual layup. Besides the precision and high quality of the manufacture, by using AFP techniques is possible to integrate features that are unconceivable to perform manually, like curved fibres to increase the bend/twist capability of a laminate. Due to the potential use of AFP techniques in many other engineering fields the demand of studies is increasing significantly.