Modal analysis of an iced offshore composite wind turbine blade

In the far north, low temperatures and atmospheric icing are a major danger for the safe operation of wind turbines. It can cause several problems in fatigue loads, the balance of the rotor and aerodynamics. With the aim of improving the rigidity of the wind turbine blade, composite materials are currently being used. A numerical work aims to evaluate the effect of ice on composite blades and to determine the most adequate material under icing conditions. Different ice thicknesses are considered in the lower part of the blade. In this paper, modal analysis is performed to obtain the natural frequencies and corresponding mode shapes of the structure. This analysis is elaborated using the finite element method (FEM) computer program through ABAQUS software. The results have laid that the natural frequencies of the blade varied according to the material and thickness of ice and that there is no resonance phenomenon.

Dynamic Analysis of the Optimized Savonius Vertical Axis Wind Turbine Composite Blades

This paper presents a comprehensive study of the dynamic behavior of small vertical axis wind turbines (VAWTs) based on local fabricated Savonius VAWTs, which is suitable for countries that have moderate wind speed. The merits of this design are cleanliness, silent, start-up under low wind speed, independent wind directions, adaptability and ease of manufacturing. Also, this paper presents an experimental validation study for the optimized Savonius VAWT. Four verification test configurations of the optimized VAWT composite blades are designed, simulated and fabricated of Glass – Polyester with different stacking sequence layout for each. Modified mechanical parameters are introduced to improve the scalability, reliability, and accuracy of the developed models. Based on wind energy conversion system basics, aerodynamic characteristics (tip speed ratio (λ) and coefficient of power (Cp)), dynamic characteristics (natural frequencies and mode shapes) of Savonius-rotor models are presented and simulated within SOLIDWORKS Simulation 2020 software. The dynamic characteristics such as frequency, mode shape and damping factor are extensively investigated using Fast Fourier Transformer (FFT) analyzer. The results show that the role of composite material blades in improving the dynamic performance of a wind turbine is significant.

Experimental analysis of high velocity impacts of composite fragments on aluminium plates

The improvement of engines is one of the ways to diminish the fuel consumption in civil aircrafts, and Open Rotors engines are one of the best promises in order to achieve a sensible efficiency increment. These engines have large composite blades that could, in the event of failure, impact against the fuselage, totally or partially. In this case, composite fragments could behave as impactors. In order to design fuselages for this event and adopt these new engines in the future, it is necessary to understand the impact behaviour of a composite fragment against a deformable structure. To this end, unidirectional and woven composites fragments were impacted at high velocity (up to 150 m/s) against aluminium panels at different impact velocities. The composite fragments were made using AS4/8552 (UD) and AGP-193PW (woven) prepregs manufactured by Hexcel Composites, both using AS4 fibres and 8552 epoxy matrix. High speed video cameras were used to record the impact process and to measure both the impact and the residual velocity and hence the energy absorbed.

The Effect of Non-Conservative Compressive Force on the Vibration of Rotating Composite Blades

This paper investigates the effectiveness of a resonance avoidance concept for composite rotor blades featuring extension–twist elastic coupling. The concept uses a tendon, attached to the tip of the blade, to apply a proper amount of compressive force to tune the vibration behavior of the blade actively. The tendon is simulated by applying a non-conservative axial compressive force applied to the blade tip. The main load carrying part of the structure is the composite spar box, which has an antisymmetric layup configuration. The nonlinear dynamic behavior of the composite blade is modelled by using the geometrically exact fully intrinsic beam equations. The resulting nonlinear differential equations are discretized using a time–space scheme, and the stationary and rotating frequencies of the blade are obtained. It is observed that the proposed resonance avoidance mechanism is effective for tuning the vibration behavior of composite blades. The applied compressive force can shift the frequencies and the location at which the frequency veering take place. Furthermore, the compressive force can also cause the composite blade to get unstable depending on the layup ply angle. Finally, the results, highlighting the importance of compressive force and ply angle on the dynamic behavior of composite blades, are presented and discussed.

Free Vibrations of Functionally Graded Graphene-Reinforced Composite Blades with Varying Cross-Sections

In this paper, free vibrations of functionally graded (FG) graphene-reinforced composite blades with varying cross-sections are investigated. Considering the cantilever boundary conditions, the dynamic model of a rotating blade is simplified as a varying cross-sections plate with pre-installed angle and pre-twisted angle. As a reinforcement, the graphene platelets (GPLs) are distributed either uniformly or gradiently on the plate along its thickness direction. The effective Young’s modulus is formulated by the modified Halpin–Tsai model. The rule of mixture is applied to calculate the effective Poisson’s ratio and mass density. The equations of motion are established by using the first-order shear deformation theory and von Karman geometric nonlinear theory. Based on the Rayleigh–Ritz method, the natural frequencies of the rotating FG blade reinforced with the GPLs are obtained. The accuracy of the present method is verified by comparing the obtained results with those of the finite element method and published literature. A comprehensive parametric study is conducted, with a particular focus on the effects of distribution pattern, weight fraction, and geometries size of the GPLs together with dimensional parameters of varying cross-sections blade on the dynamics of the FG blades reinforced with the GPLs.

Modeling and Optimization for the Dynamic Performance of Vertical-Axis Wind Turbine Composite Blades

This article presents a study of modeling and optimization for the dynamic performance of wind turbine composite material blades and investigates the effects of composite material stacking sequence in addition to some design parameters such as twist angle (ɸ) and aspect ratio (AR) on the whole wind turbine performance. The two-stage Savonius rotor VAWT composite blades are designed and simulated within the solidworks simulation 2020 package. Modified mechanical parameters are introduced to improve the scalability, reliability, and accuracy of the developed models. The lamination plate theory is used to compute the equivalent mechanical properties for each composite blade. The finite element analyses (FEAs) are conducted to investigate the dynamic characteristics (frequency and associated mode shapes) of wind turbine models. Taguchi tools such as analysis of variance (ANOVA), signal-to-noise (S/N) ratio and additive model were employed to evaluate and obtain the significant factors and determine the optimal combination levels of wind turbine design parameters. Mathematical modeling based on response surface methodology (RSM) has been established. The analysis of results shows that the aspect ratio with a contribution of 48.08% had the dominant impact on the rotor performance followed by the stacking sequence and twist angle.