Marine propellers have traditionally been manufactured from metallic alloys; however, the use of fiber-reinforced polymer composites in marine propellers has recently been extensively investigated. These composite materials provide excellent strength-to-weight and stiffness-to-weight ratios, improved fatigue performance, and reductions in corrosion, noise generation, and magnetic signature. Another advantage of composites is their increased mechanical flexibility relative to metals and thus their capacity to deform based on flow conditions, rotational velocity, and laminate design [1]. This ability to deform permits passive or active shape adaptation, obviating the need for complex mechanisms such as in controllable pitch propellers.

Despite their advantages, composite propellers are vulnerable to flaws such as voids or delaminations that may occur during or after manufacturing. The blades are also susceptible to damage caused by impact, vibration, twisting, and fatigue. While the damage may be invisible at the surface of the material, delamination within the composite can significantly reduce the performance of the material and may cause catastrophic failure of the structure. To reduce these risks, embedded Fiber Bragg Grating (FBG) sensors can be used to detect damage within composite structures and to provide real time information about the blade performance. Fiber optics are lightweight, small in size, immune to electromagnetic interference, and have been proven to successfully measure strain [2].

The use of fiber optic sensors for real time deformation and damage detection is most effective when informed by a high fidelity numerical model. To that end, a coupled fluid-structure interaction model is presented in this paper. The numerical model combines the computational fluid dynamics solver FineMarine developed at Centrale Nantes, France with a modal structural analysis directly implemented into the CFD code [3]. The coupled model is solved in time with options for both a quasi-steady and fully unsteady approach, allowing the user to optimize the solver for computational efficiency or high resolution as necessary. The coupled simulation will be used to inform a set of towing tank experiments of a single, non-rotating composite propeller blade to be performed at Central Nantes. It is essential to highlight that, as a first step, this configuration will not fully represent a rotating blade ; i.e, it will not take into account the spanwise variation of velocity due to rotation. Due to the highly twisted nature of a propeller blade as compared to a hydrofoil, however, a higher level of multi-scale dynamic excitation in the flow and in the hydroelastic response of the blade can be expected. The method will later be extended to include the study of flexible, variable-stiffness, and rotating propeller blades.

[1] Young, YL, Motley, MR, Barber, RB, Chae, EJ, & Garg, N. (2016). Adaptive composite marine propulsors and turbines: progress and challenges. Applied Mechanics Reviews, Vol 68, p 060803.

[2] Wildy, S, Cazzolato, B, & Kotousov, A. (2010), Detection of delamination damage in a composite laminate beam utilising the principle of strain compatibility, Key Engineering Materials, Vol 417-418, p 269-272.

[3] Mounton, L, Leroyer, A, Deng, GB, Querty, P, Soler, T, & Ward, B. (2018) Towards unsteady approach for future flutter calculations. Journal of Sailing Technology, Vol 7, p 2018-07.