Wind Turbine Blade Manufacturing Research Articles

Active thermography for the interpretation and detection of rain erosion damage evolution on GFRP airfoils

Defects such as voids, which may occur during the manufacturing of wind turbine blades, have a significant impact on premature rain erosion, especially at the leading edge. Active thermography offers the potential for non-contact in-situ inspection of rotor blade leading edges. Thermographic investigations on curved and coated GFRP specimens have shown that sub-surface defects not only represent a susceptibility to erosion, but that the onset of erosion is dependent on the depth of the defects. Furthermore, the damage development of sub-surface towards surface defects can be visualized, which allows the damage stage to be assigned to an erosion stage.

CFD analysis and experimental investigation to determine the flow characteristics around NACA 4412 airfoil blades at different wind speeds and blade angles

An aerodynamically efficient blade is one of the prime necessities to extract the maximum mechanical power from a wind turbine. A number of researches are available in the literature studying blade design and configuration to improve aerodynamic characteristics of horizontal axis wind turbines. Less attention, however, has been devoted to wind turbines in terms of simultaneous optimization of blade and airfoil angles. The present study is important for the aerodynamic design and manufacturing of wind turbine blades. In this regard, various blade angles have been numerically simulated to determine the optimum blade angle. In addition to numerical analysis, experimental tests have been done to investigate NACA 4412 blade angle. As a result of this study, it was observed that blade angle in the range of 5°–10° showed the best performance among the tested various blade angles.

Multi-objective optimization and modeling of a natural fiber hybrid reinforced composite (PxGyEz) for wind turbine blade development using grey relational analysis and regression analysis

Due to the increasing demand for clean and sustainable energy, wind turbine technology has also witnessed significant developments in terms of its output capacity which is proportional to its size (length of wind turbine blades). The only limitation to this scaling is the availability of applicable materials with expected strength and low weight which can support a longer span wind turbine blade. Although studies have been carried out on alternate materials for the development of wind turbine blades, the use of Grey Relational Analysis for the optimization of natural fiber-reinforced composites for this application is rare. Also, pineapple leaf fiber, having considerable mechanical properties and low density has not been optimally considered as reinforcement in this regard. This is a robust study concerned with developing more eco-friendly materials for application in the manufacture of wind turbine blades. In this study, a material PxGyEz, a natural fiber/synthetic fiber polymer composite was developed and optimized based on the major criteria for selecting materials for wind turbine blades which are high tensile strength, high flexural strength, and low density. Grey relational analysis coupled with the Taguchi robust optimization technique was used for the optimization process and statistical analysis was employed to know the percentage contribution of each of the variable parameters (PALF volume percentage, glass fiber volume percentage, and fiber length) to the grey relational grades. The material P10G20E15 was the optimum having a grey relational grade of 0.7977 at experimentation and tensile strength of 95.3144 MPa, a flexural strength of 92.818 MPa, and a density of 1.3274 g/cm3. SEM analysis showed microstructural formations that explained the mechanical and physical behavior of the optimized hybrid composite. Simulation of an NREL 5 MW wind turbine blade developed with the optimized material P10G20E15 proved reliable for service with a 64% reduction in weight.

Anomaly Detection during Thermoplastic Composite Infusion: Monitoring Strategy through Thermal Sensors

Vacuum assisted resin infusion (VARI) processes are widely used for the fabrication of large composite parts. For some years now, wind blades are designed with thermoset composite materials, however, recyclability is often the missing brick. The recent advent of thermoplastic materials such as ELIUM©, developed by ARKEMA, shows the possibility to consider the manufacture of very large parts such as wind turbine blades with recyclable constituents [1]. The French institute IRT Jules Verne is leading the research project ZEBRA, with a consortium of industrials, focusing on different thematics of the manufacturing of wind turbine blades, including process monitoring. In the objective of evaluating the possibility for anomaly detection during the ELIUM© infusion process, an infusion test bench was developed, equipped with different sensors including infrared camera, thermocouples and heat flow sensors. In this work, the thermal sensors are evaluated by the study of several infusion scenarios of plates fabricated under different process conditions and material parameters. Artificial anomalies are imposed into the process to evaluate the potential of these sensors to detect the induced disturbances. A numerical process modelling is developed, compared to the sensor outputs and used to achieve a better understanding of some effects observed during the process.

Simulation of Wrinkling during Forming of Binder Stabilized UD-NCF Preforms in Wind Turbine Blade Manufacturing

Binder stabilized preforms are getting increased attention in the wind turbine industry with the aim to increase automation in the production of large blades. In this context a preform is a stack of dry unidirectional glass fiber non-crimp fabrics (UD-NCF), which is consolidated using a polymeric binder. The preform is manufactured in a separate mold, and subsequently placed in the main blade mold. During placement of preforms, fiber wrinkling may occur due to the deformation of the preform. To accommodate this problem, we propose a predictive simulation model that can be used to investigate how different process parameters influence the wrinkle creation. Most forming simulation models in the literature consider frictional laws in the inter-ply interface for multi-layered fabrics. In this work the binder interfaces between the layers are modelled using a cohesive traction-separation law to accurately model binder degradation and wrinkle creation during preform deformation. The model predictions are compared with full thickness preform coupon specimens.

Structural Design of Wind Turbine Blades with an Additively Manufactured Graded Lattice Core using Topology Optimisation

Conventional wind turbine blade manufacture relies on large, expensive moulds. Instead, using additive manufacturing to print the internal structure of blades, upon which it would be possible to lay composite plies, could significantly reduce manufacturing costs and, as one could “3D print” topologically optimal designs, improve structural efficiency. In general, topology optimisation integrates well with additive manufacturing. There are, however, two main challenges associated with the adoption of topology optimisation in wind blade design, i.e. accounting for: (i) the aeroelastic response of blades; and (ii) the variety of different materials that would be employed, in the composite laminates as well as the printed structure. To address these challenges, the present paper proposes a new multi-step design and optimisation framework relying on the combination of three software. First, a conventional aero-servo-elastic model is used to evaluate blade loads and displacements. Next, a topology optimisation software is used to optimise the blade laminates and core structure. Third, a lattice generator is used to convert the topological optimised “grey” design into an equivalent cellular design that can be printed using additive manufacturing. The full methodology of this design framework and an initial proof-of-concept topology optimisation solution are presented in this paper.

Virtual Prototyping: Evaluating the Digital Twin Based Virtual Factory for New Product Introduction

Shortening lifecycles and increasing complexity make product and production lifecycle processes more challenging than ever for manufacturing enterprises. Virtual Prototyping (VP) technologies promise a viable solution to handle such challenges in reducing time and physical builds as well as increasing quality. In previous studies, the Digital Twin (DT) based Virtual Factory (VF) concept showed significant potential to handle co-evolution by integrating 3D factory and product models with immersive and interactive 3D Virtual Reality (VR) simulation technology as well as real-time bidirectional data synchronisation between virtual and physical production systems. In this article, we present an extension to the paper “Demonstrating and Evaluating the Digital Twin Based Virtual Factory for Virtual Prototyping” presented at CARV2021. The study presents an evaluation by industry experts of the DT based VF concept for VP in the context of New Product Introduction (NPI) processes. The concept is demonstrated in two cases: wind turbine blade manufacturing and nacelle assembly operations at Vestas Wind Systems A/S. The study shows that the VF provides an immersive virtual environment, which allows the users to reduce the time needed for prototyping. The industry experts propose several business cases for the introduced solution and find that the phases that would have the most gain are the later ones (production) where the product design is more mature.

Analysis of Number of Layers and Volume Fraction of Fiber Against Shock Load and Composite Compressive Strength Wind Turbine Propeller

The manufacture of wind turbine blades has a very high risk of failure, especially in the manufacturing section or in this case the material structure. If the structure of the propeller material is not able to withstand the very high pressure and air flow, it will result in the failure of the material structure when it is in use. For this reason, the purpose of this study was to determine the composition of composite materials that have high strength and toughness properties and are suitable for wind turbine propellers. The method used in this research is experimental. The independent variables include the number of layers and the volume fraction of straw fiber. The dependent variables are shock load and compressive strength. Each compression test specimen is made with a gauge length of 100mm, a width of 25mm, and a thickness of 2.5mm. While the impact test specimens are made equal to l25mm long, l2mm wide, l2mm high, and 2mm notch. The results showed that the bending strength of the straw fiber composite with 6 layers had an increasing trend as the number of layers increased. The highest bending strength with the number of piles of 6 layers and the lowest strength with the number of piles of 2 layers. In addition, the volume fraction is very influential on the bending stress of the straw composite matrix. It can be seen that the matrix with a volume fraction of 50% has the greatest bending stress in each number of layers, both 2, 4 and 6. For the impact test, it is found that the optimal number of layers occurs in the number of 2 layers with a volume fraction of 33%. The shock load tends to decrease. Meanwhile, based on the volume fraction, the larger the volume fraction, the smaller the shock load that can be received by the straw fiber composite material.

Influence of out-of-plane fiber waviness and different environmental conditionings on mechanical and morphological characteristics of fiber glass/epoxy laminates

The use of structural polymeric composites constitutes an interesting option in the area of wind turbine blade manufacturing. Nevertheless, thick composite components may present out-of-plane waviness in their fibers, compromising the service life of the wind blades. In this context, the present study aims to study the influence of out-of-plane waviness in the fibers with different degrees of severity as well as to verify the effect of fiber glass/epoxy resin composites immersion in distilled water and saline solution in their tensile strength (σmax), modulus of elasticity (E), and deformation at break (єrup), analyzing the reinforcement/matrix interface changes. The results showed that the increase in severity promoted, in general, a statistically significant deterioration in σmax of the samples exposed to the same environmental conditioning. The conditioning led to a decrease in E and an increase in єrup, attributed to the deterioration of the interface and the plasticization of the polymeric matrix, respectively, as evidenced by fractographic analysis. The effect of severity on the єrup and σmax properties was only noticed in laminates exposed to environmental conditioning, due to water sorption favoring the deterioration of the matrix/reinforcement interface, intensifying the deleterious effect of out-of-plane waviness of fibers.

Integrated AHP-TOPSIS methods for optimization of epoxy composite filled with Kota stone dust

In this research article, Hybrid MCDM approaches like AHP (analytical hierarchy process) and TOPSIS (technique for order preference by the resemblance to an ideal solution) methods are used to rank Kota stone dust filled epoxy composites. Physical properties like density, water absorption rate and mechanical properties like hardness, compressive strength, flexural strength and tensile strength are evaluated. Relative weights of criteria are obtained using AHP technique and consistency index and consistency ratio are calculated. AHP is a multi-criteria assessment method which organizes decision-making and simplifies it. Later TOPSIS method is used to select best epoxy composite for fabrication of wind turbine blades. Finally, it is estimated that the most appropriate epoxy composites for the manufacturing of wind turbine blades are epoxy with 20 wt% of Kota stone dust.

Delamination Fracture Behavior of Unidirectional Carbon Reinforced Composites Applied to Wind Turbine Blades

One of the materials that is used widely for wind turbine blade manufacturing are fiber-reinforced composites. Although glass fiber reinforcement is the most used in wind turbine blades, the use of carbon fiber allows larger blades to be manufactured due to their better mechanical characteristics. Some turbine manufacturers are using carbon fiber in the most critical parts of the blade design. The larger rotors are exposed to complex loading conditions in service. One of the most relevant structures on a wind turbine blade is the spar cap. It is usually manufactured by means of unidirectional laminates, and one of its major failures is the delamination. The determination of material features that influence delamination initiation and advance by appropriate testing is a fundamental topic for the study of composite delamination. The fracture behavior is studied across coupons of carbon fiber reinforcement epoxy laminates. Fifteen different test conditions have been analyzed. Fracture surfaces for different mode ratios have been explored using optical microscope and scanning electron microscope. Experimental results shown in the paper for critical fracture parameters agree with the theoretically expected values. Therefore, this experimental procedure is suitable for wind turbine blade material characterizing at the initial coupon-scale research level.

Designing a test rig for structural static-load testing of small horizontal axis wind turbine rotor blades

This paper presents a design of a test rig for structural static load testing of small horizontal wind turbine blades. It is a next step after the success of the DeVie project, a join-research project to boost the wind energy knowhow between Germany and Vietnam. According to the IEC-61400-23 standard for full scale structural testing of rotor blades, and based on existing facilities of HCMUT, especially the aerospace engineering lab. and the engineering mechanics lab., we propose a prototype of a test-rig for structural static load testing of rotor blades. A rotor blade of 4 meters in length, manufactured by China, is used in the case study of our structural static-load test-rig. This paper used the reverse engineering method to determine the blade geometry and performance, since the blade was provided and not designed from scratch. Detailed steps to determine the test load for the rig are the most important, based on the blade design and the wind condition of Vietnam, a study case was set to start the process. Since that required a lot of experience and know-how, beside the work and research from our university, other critically important information was kindly provided by the German's experts in the field. Result of the blade tip displacement are wildly used in this industry to validate the blade design. Our test rig result in 0.289 meters were compared to the reverse engineering and simulation result of 0.28 meter with QBlade/FAST in the same blade loading shown well similarity, this result validated our work process. Future revision of the test rig is promised to provide more function such as fatigue test mode, higher load capacity, faster testing time as well as more accurate result, aiding the domestic market of composite wind turbine blade manufacturing which is still in its infancy.

Development of a numerical model of a novel leading edge protection component for wind turbine blades

Abstract. As the world shifts to using renewable sources of energy, wind energy has been established as one of the leading forms of renewable energy. However, as wind turbines get increasingly larger, new challenges within the design, manufacture and operation of the turbine are presented. One such challenge is leading edge erosion on wind turbine blades. With larger wind turbine blades, tip speeds begin to reach over 300 km h−1. As water droplets impact along the leading edge of the blade, rain erosion begins to occur, increasing maintenance costs and reducing the design life of the blade. In response to this, a new leading edge protection component (LEP) for offshore for wind turbine blades is being developed, which is manufactured from thermoplastic polyurethane. In this paper, an advanced finite element analysis (FEA) model of this new leading edge protection component has been developed. Within this study, the FEA model has been validated against experimental trials at demonstrator level, comparing the deflection and strains during testing, and was found to be in good agreement. The model is then applied to a full-scale wind turbine blade and is then modelled with the LEP bonded onto the blade's leading edge and compared to previously performed experimental trials, where the results were found to be well aligned when comparing the deflections of the blade. The methodology used to develop the FEA model can be applied to other wind blade designs in order to incorporate the new leading edge protection component to eliminate the risk of rain erosion and improve the sustainability of wind turbine blade manufacture while increasing the service life of the blade.

Prediction of Mechanical Performance of Natural Fibers Polypropylene Composites: a Comparison Study

The future trends of wind turbine blade materials are mostly centered around utilizing lighter materials with improved life cycle and low cost. In modern wind turbine blade, using green composite or biocomposite is a sustainable solution, especially for small wind turbine blade with natural fiber and biodegradable polymer. In this work, four natural fibers (Alfa, Flax, Sisal and Hemp) are used with Polypropylene (PP) thermoplastic polymer. The objective is to evaluate the elastic muduli of composite by two methods; Analytical Mori Tanaka theory and numerical with Digimat MF. The results show a good validation between the two methods. The comparison of the mechanical behaviour of the transversely isotropic of natural fibers indicate that the hemp have a good performance with high Young and shear modulus regarding to their low density, which can offer an excellent candidate for the manufacturing of small wind turbine blades in rural and isolated areas.

Understanding the Solid–Ice Interface Mechanism on the Hydrophobic Nano-Pillar Structure Epoxy Surface for Reducing Ice Adhesion

Ice accumulation on wind turbine blades reduces power generation efficiency and increases wind turbines’ maintenance cost, even causing equipment damage and casualties. In this work, in order to achieve passive anti-icing, a series of nano-pillar array structures with different diameters of from 100 to 400 nm and heights of from 400 to 1500 nm were constructed on the substrate bisphenol-A epoxy resin, which is generally used in the manufacturing of wind turbine blades. The as-constructed functional surface showed excellent water repellence, with a contact angle of up to 154.3°. The water repellence on the nano-pillar array structures could induce ultra-low ice adhesion as low as 7.0 kPa, finding their place in the widely recognized scope of icephobic materials. The underlying solid–ice interface mechanism was well revealed in regard to two aspects: the interface non-wetting regime and the stress concentration behavior on the nano-pillar array structured surface. A detailed discussion on both the factors presented here will help surface structure design and function of icephobic materials, especially for epoxy-based composite materials.

Cure simulations of thick adhesive bondlines for wind energy applications

AbstractCuring of adhesive bondlines is a critical and time‐consuming operation in wind turbine blade manufacturing. Significant variation in adhesive thickness can lead to important differences in thermal histories trough the adhesive bonds due to the exothermic nature of the cure process. Reducing bondline cure cycle time and avoiding adhesive overheating are two competing factors in the design of cure temperature cycles. Predictive models on the impact of adhesive thickness variability in bondline cure temperature cycle is currently limited. Adhesive curing and temperature evolution can be simulated by finite element (FE) models coupling the heat transfer problem with the cure kinetics of the adhesive. The cure kinetics of the adhesive system was characterized by isothermal differential scanning calorimetry experiments and implemented in the FE software Abaqus/CAE by user subroutines. Predictions from the FE model were validated experimentally against temperature readings from the curing of 10, 20, and 30 mm thick adhesive bondlines. To highlight the role that predictive models potentially have in the optimization of bondline cure cycles a 2D cross section model representing the trailing edge of a wind turbine blade was used as case study. It was demonstrated that computational models enable customizing cure profiles for nonuniform adhesive thicknesses, ensuring fully cured bondlines with acceptable mechanical properties.

Modelling of chemical shrinkage evolution with curing degree of a filled epoxy adhesive

An epoxy adhesive system, commonly used in wind turbine blade manufacturing, is experimentally investigated with respect to its chemical shrinkage behavior to show the shrinkage evolution within rotor blade production related process conditions. Therefore, a new test configuration is set up to record the resulting chemical shrinkage of the adhesive at cross-linking temperatures ranging from 20°C to 90°C. The respective conversion evolution is simulated under several temperature conditions through a curing kinetics model. This is generated with state of the art formulations, implementing test results from a differential scanning calorimeter (DSC). Moreover, the transformation of the curing degree to the corresponding glass transition temperature (Tg ) is performed through an experimentally based Di-Benedetto curve-fitting. By the combination of curing kinetics and chemical shrinkage test data, a model for the temperature and conversion dependant chemical shrinkage evolution during cure is developed. This is applied to a realistic curing cycle for adhesive materials in rotor blade production.

Adhesive curing cycle time optimization in wind turbine blade manufacturing

The curing of adhesives in wind turbine blades is a cost and time-intensive manufacturing step. Bondlines are critical to the structural integrity of the blade, but substantial variation in bondline thickness can result in different thermal histories and even degradation of the adhesive due to its exothermic reaction. Models to predict the thermal behavior of adhesive bondlines during the curing step, taking manufacturing conditions and variation in thickness into account, are needed to minimize cure times while avoiding excess temperature. In this study, a finite element model capable of tracing the thermal and conversion histories of the adhesive was developed. Standard heat transfer equations were coupled with cure kinetics in the model through user subroutines, and the cure kinetics were characterized and validated experimentally. A 2D cross-section model of a wind turbine blade was created to simulate the adhesive curing cycle in a manufacturing setting. This model was used to highlight critical aspects of the curing cycle and test methods to shorten the cycle time while maintaining the integrity of the bond. Several improvement methods and their potential cycle time savings were investigated, such as implementing individual heating and cooling zones for each adhesive area and additional spar cap heating/cooling.

The alternative energy Technosphere safety problems

The work shows that the dangerous vulnerability of renewable energy sources is the imperfection of materials and design of energy storage devices. A study of the charge-discharge cycles’ effect on the batteries’ stability in a specially developed installation showed that if even the most promising lithium-ion devices are used, due to the microdamage accumulation, all electric energy storage devices will not be durable and will necessarily fail. In addition, it is shown that the materials used in the manufacture of solar panels and wind turbine blades can harm the environment. It is concluded that the Technosphere safety problems of alternative energy can be solved only if the technology for the efficient utilization of used solar batteries and blades of wind-powered generators is created.

Performance analysis of a small horizontal axis wind turbine under the use of linear/nonlinear distributions for the chord and twist angle

The increase in efficiency, decrease in starting time, and ease in manufacturing of rotor blades are the most desirable aims of research in the design of small-scale wind turbines. A multi-objective optimization study is carried out to analyze the performance of a small horizontal axis wind turbine in terms of the output power and the starting time for four possible combinations of linear/nonlinear distributions of the chord length and twist angle along one-meter timber blades. The blade-element momentum theory is adopted for the calculation of the power coefficient and the starting time. The optimization is achieved through a genetic algorithm which simultaneously maximized the power coefficient and minimized the starting time. The most important contribution of this paper is the in-depth comparison of the linear and the nonlinear distributions for chord and twist angle subjected to the aforementioned optimization, which is not available in the existing literature in such detail. Results show that although the linear distributions have more deviation from the so-called ideal distributions, however, the output power performance of the blades with linear distributions is competitive with that of the nonlinear ones. Moreover, the results establish that the use of linear distribution can improve the starting performance at a lesser compromise of output power. This is of paramount importance, particularly to promote harnessing the wind energy in developing countries, as simpler distributions could facilitate the manufacturing of wind turbine blades. Apart from using the linear or nonlinear distributions for both the chord and the twist angle, two other cases are also investigated including the linear distribution for the chord and the nonlinear one for the twist and vice versa. The analysis of these cases shows that choosing the nonlinear distribution for the chord would improve the starting while using the linear one would lead to more powerful blades.