Parametric Study of Accidental Impacts on an Offshore Wind Turbine Composite Blade (original) (raw)
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Analysis of impact induced damage in composites for wind turbine blades
2015 Power Generation System and Renewable Energy Technologies (PGSRET), 2015
Glass fabric-reinforced polymer (GFRP) composites used in wind turbine blades are usually exposed to large-deflection bending impacts caused by wind storms, heavy rainfall, water splashes and hailstones in the offshore; and sand and dust impingement in the desert environments. Such loadings can cause deterioration of structural integrity and load-bearing capacity of the blade structure due to induced damage in the form of matrix cracking, delamination and fibre fracture. These types of damage mechanisms become more detrimental and pose a threat to the fatigue life of the turbine blades. In this work, first the load-bearing and energy absorbing capability of woven GFRP laminates is investigated under impact loading. Experimental tests are conducted to characterise the behaviour of GFRP composites under large-deflection dynamic bending in Izod type impact tests using Resil impactor. Impact tests are performed at various energy levels to determine the ultimate fracture toughness of the laminates. In these tests, the material demonstrated interply delamination damage due to weaker matrix at low energy levels. At higher impact energies, apart from delamination, the material also exhibited permanent deflection instead of catastrophic fabric fracture. The latter was due to the visco-elasto-plastic nature of the glass fibres apart from the thermoplastic matrix. The deformation behaviour and delamination damage ensued by dynamic loading is also studied by developing three-dimensional finite element (FE) model in Abaqus/Explicit commercial package. In FE model, multiple layers of bilinear cohesive-zone elements are defined at the damage locations. Stress-based criteria and fracture-mechanics techniques are used to assess damage initiation and its progression, respectively. Numerical results gave good correlation when compared to the dynamic response observed in experiments. The methodology developed here can be employed in damage tolerant design of wind turbine composite blades subjected to similar impact loading conditions.
Numerical simulation of progressive damage in composite wind turbine blade under aerodynamic loads
2022 19th International Bhurban Conference on Applied Sciences and Technology (IBCAST), 2022
A constitutive model based on the concept of continuum damage mechanics has been proposed to study the progressive damage behavior of composite laminates under ballistic impact. The proposed model is investigated in five steps: First, the quadratic form of damage initiation criteria are presented to predict the initiation of failure in different modes. Second, an exponential form damage evolution law combined with characteristic length based fracture energy approach has been presented. Stiffness degradation is characterized by a variable determined by the equivalent displacement for each failure mode. Third, an experimentally verified strain rate model that considers the rate dependency of the strength and modulus of the composite laminate is considered. Fourth, cohesive elements are inserted at every inter-layer for modeling the delamination evolution. Fifth, the constitutive model has been combined with an element erosion algorithm for the removal of highly distorted elements. Simulations have been performed using reduced integration hexahedra elements (RIHE) and full integration hexahedra elements (FIHE). Implementation of cohesive elements exhibited better delamination progression. Experimentally verified strain rate model enhanced the efficiency of the model showing good correlation between the present simulations and experimental observations, in terms of damage patterns, residual velocity, kinetic energy and ballistic limit.
A Comprehensive Analysis of Wind Turbine Blade Damage
Energies
The scope of this article is to review the potential causes that can lead to wind turbine blade failures, assess their significance to a turbine’s performance and secure operation and summarize the techniques proposed to prevent these failures and eliminate their consequences. Damage to wind turbine blades can be induced by lightning, fatigue loads, accumulation of icing on the blade surfaces and the exposure of blades to airborne particulates, causing so-called leading edge erosion. The above effects can lead to damage ranging from minor outer surface erosion to total destruction of the blade. All potential causes of damage to wind turbine blades strongly depend on the surrounding environment and climate conditions. Consequently, the selection of an installation site with favourable conditions is the most effective measure to minimize the possibility of blade damage. Otherwise, several techniques and methods have already been applied or are being developed to prevent blade damage, ...
Composite Structures, 2020
The high demand of low cost wind energy needs to design large scale turbine blades with reduced weight which poses great challenges to their structural integrity while prone to extreme wind gusts. The loading can cause large-deflection bending and damage leading to significant drop in the load-bearing ability of long composite wind turbine (WT) blades. In this study, a comprehensive finite element (FE) modelling procedure is developed to simulate structural integrity and damage in composite blade using ANSYS software. The three-dimensional blade model is analyzed by carrying out geometrically nonlinear FE analysis to investigate the blade deformation and highly stressed regions leading to possible failure modes. The results show that the blade suction side is subjected to high compressive stress causing local skin buckling, which is further investigated using linear buckling analysis. Such local buckling drives interfacial debonding between skin and spar joined with a weak adhesive. Subsequently, the interfacial damage in the identified critical region is modelled by developing a damage submodel employing cohesive zone model (CZM) approach at the skin-spar interface. The analysis results indicate that buckling driven skin-spar debonding at adhesive interface is initial damage mode which can lead to progressive failure of the blade structure. Consequently, the ultimate load bearing capacity of WT blade is governed by a coupled buckling and debonding phenomenon even at load level below the ultimate design load. The simulation methodology adopted in this study can be employed to develop reliable and cost-effective computational tools for analyzing structural integrity and assessing damage in blade structure than expensive experimental testing.
Damage mitigation techniques in wind turbine blades: A review
Wind blades are major structural elements of wind turbines, but they are prone to damage like any other composite component. Blade damage can cause sudden structural failure and the associated costs to repair them are high. Therefore, it is important to identify the causation of damage to prevent defects during the manufacturing phase, transportation, and in operation. Generally, damage in wind blades can arise due to manufacturing defects, precipitation and debris, water ingress, variable loading due to wind, operational errors, lightning strikes, and fire. Early detection and mitigation techniques are required to avoid or reduce damage in costly wind turbine blades. This article provides an extensive review of viable solutions and approaches for damage mitigation in wind turbine blades.
Volume 10: Ocean Renewable Energy, 2018
Structural analysis of floating wind turbines is normally carried out with the hull considered as a rigid body. This paper explores the consequences of modeling the pontoons of a tension leg platform (TLP) wind turbine as flexible structures. The analysis is based on numerical simulations of free decays, structural response to wave excitation and short-term fatigue damage accumulation at chosen points of the platform. In addition, the importance of considering hydroelasticity effects is evaluated. It is observed that pontoon flexibility can change the platform natural periods significantly, as well as the intensity and peak frequencies of internal structural loads. The adoption of a fully rigid-body is shown to be non-conservative for the fatigue damage analysis. Loads due to hydroelasticity have order of magnitude comparable to those related to rigid-body motions, but still lower enough to be considered of secondary importance.
This paper presents the results of research of the microstructure of the composite blade W55RBVS for the wind turbine of up to 6kW power after structural testing up to failure. The first part of the testing consists of the static testing of the structure up to the moment of the blade failure. The aim of the first part of the test is to define rigidity of the blade W55RBVS, to determine the maximum force which leads to faliure and the relative span of the blade failure. Blade testing is performed in the Aerotechnics Laboratory of the Faculty of Mechanical Engineering, Belgrade University. The second part of the testing consists of comparing the critically loaded part with sub‐critically loaded part. This test was carried out by atomic force microscopy (Eng. Atomic Force Microscopy‐AFM). All the results and analysis are presented in this paper. The test result will be used to redesign the blades.
Failure Analysis of Small Composite Sandwich Turbine Blade Subjected to Extreme Wind Load
Procedia Engineering, 2011
In this paper, the progressive failure process of composite sandwich wind turbine blades subjected to wind load is studied via both theoretical and experimental approaches. In the theoretical study, the wind pressure acted on the wind blade surface is estimated in an aerodynamic analysis. The stresses in the wind blade are determined using the finite element code ANSYS in which the skin and the core of the blade are modeled using shell and solid elements, respectively. A phenomenological failure criterion is adopted to predict the first-ply failure strength of the blade. After the occurrence of the initial failure, the material properties at the failure locations are modified following a material degradation rule. The updated stiffness matrix of the blade is then obtained with the consideration of the changes of the material properties and configuration of the blade. An incremental load approach together with a sequential stiffness adjustment technique is used to trace the load-displacement curve and thus determine the ultimate strength of the blade. In the experimental investigation, a composite sandwich wind blade was fabricated for strength testing. In the test, the Whiffle-tree approach was used to simulate the wind load on the blade. The measured ultimate load of the wind blade was then used to validate the accuracy of the proposed method for failure analysis of composite sandwich wind blades.