Experimental Verification of the Elastic Response in a Numeric Model of a Composite Propeller Blade with Bend Twist Deformation

Abstract

Adaptive composite propeller blades showing bend twist behaviour have received increasing interest from hydrodynamic and structural engineers. When exposed to periodic loading conditions, such propellers can be designed to have higher energy efficiency and emit less noise and vibration than conventional propellers. This work describes a method to produce an adaptive composite propeller blade and how a point load experiment can verify the predicted elastic response in the blade. A 600 mm-long hollow full-size blade was built and statically tested in the laboratory. Finite element modelling predicted a pitch angle change under operational load variable loads of 0.55°, a geometric change that notably compensates for the load cases. In the laboratory experiment, the blade was loaded at two points with increasing magnitude. The elastic response was measured with digital image correlation and strain gauges. Model predictions and experimental measurements showed the same deformation patterns, and the twist angle agreed within 0.01 degrees, demonstrating that such propellers can be successfully built and modelled by finite element analysis.

Designing Composite Adaptive Propeller Blades with Passive Bend–Twist Deformation for Periodic-Load Variations Using Multiple Design Concepts

“…Therefore, experimental verification of the blade’s structural response, computational fluid dynamics with two-way FSI to estimate the hydrodynamic performance properties and experimental verification of the hydrodynamical properties were out of this scope. Nevertheless, it is reasonable to assume that the final design and a physical prototype of the design would show similar deformation characteristics, as a previously proposed propeller-blade model using the same design method had been experimentally verified with regard to the structural elastic response [ 27 , 28 , 29 , 37 ]. Ultimately, the blade twist in the proposed design is more prominent with regard to the absolute values and bend–twist coefficient than in previous studies.…”

“…The finite element analysis (FEA) used in this paper is performed with the FEA software Abaqus 2017 by Systema Dassaults [ 36 ]. An Abaqus FEA methodology is applied based on FEA methods that have been explored and experimentally verified in previous publications [ 8 , 27 , 28 , 29 , 37 , 38 ]. The paper that explored the experimental verification of the FEA method on a composite propeller was previously published in Polymers [ 38 ].…”

“…After exploring the design concepts of the generalized NACA model, the concepts are applied to the bend–twist propeller-blade design for a typical metal propeller-blade geometry. This propeller blade is a commercial metal-blade design that has been used in the published literature [ 8 , 27 , 28 , 37 ]. The blade design has several unique propeller geometry features, such as a significant blade skew, a varying sectional foil profile along the blades span and a propeller radius of 650 mm.…”

“…The fact that a larger twist change was required at lower blade lengths complicated the design challenge, as propeller blades usually deflect the most at the tip, and if the twist is related to the deflection, the blades will twist the most at the tip. Furthermore, in previous work on bend–twist propeller blades, the twist has usually been largest at the blade’s tip [ 5 , 8 , 13 , 27 , 28 , 37 , 38 ]. Therefore, trying to ease the twisting at the blade’s tip in the final propeller-blade design is suggested to not overcompensate for the inflow variations at larger radii.…”