Wind Turbine Blade Manufacturing Research Articles

Using piezoresistive pressure sensors for resin flow monitoring in wind turbine blades

The production of large wind turbine blades is a costly and time-consuming process. In order to obtain high-quality products and to avoid dry spots, it is necessary to monitor the resin flow during the resin infusion process. Using piezoresistive pressure sensors to perform in-situ measurement of the pressure gradient gives live information about the textile impregnation status during the manufacturing process and enables instant reaction if some anomalies are discovered. In this work, the effects of the used sensors on the static mechanical properties and the fatigue behaviour of the used glass fibre composites were investigated. The sensors were used during the manufacturing of large sandwich panels similar to that used in wind turbine blades. It was found, that the used sensors do not degrade the mechanical performance of the used materials and they are able to measure the pressure gradient during the manufacturing of wind turbine blades and to give information about the progress of the resin front.

Development of thermal residual stresses during manufacture of wind turbine blades

Thermal residual stresses have a major impact on the bond line fatigue of wind turbine blades, which can initiate tunneling cracks in the adhesive layer of the bond lines early in the operational life of the blade. This work investigates the simulation accuracy for predicting thermal residual stresses within a thick bond line. The trailing-edge bond line strip of a 34 m blade was modeled with classical laminated plate theory (CLT) on the one hand and with finite element (FE) plate models of different fidelities on the other. For the model benchmark, the thermal residual stresses were on the basis of a thermal simulation. These develop during the cooling after a typical curing cycle of a wind turbine blade manufacturing process. It was found that the analytical model on the basis of CLT was in good agreement with the plate models of higher fidelity. Additionally, a full 3D FE blade model was used to calculate the shape distortion and the thermal residual stresses. It was found that the analytical model, which did not take into account effects stemming from the whole blade structure, underestimated the full 3D FE model.

An Acoustic Source Model for Applications in Low Mach Number Turbulent Flows, Such as a Large-Scale Wind Turbine Blade

Aerodynamic noise from wind turbine blades is one of the major hindrances for the widespread use of large-scale wind turbines generating green energy. In order to more accurately guide wind turbine blade manufacturers to optimize the blade geometry for aerodynamic noise reduction, an acoustic model that not only understands the relation between the behavior of the sound source and the sound generation, but also accounts for the compressibility effect, was derived by rearranging the continuity and Navier–Stokes equations as a wave equation with a lump of source terms, including the material derivative and square of the velocity divergence. Our acoustic model was applied to low Mach number, weakly compressible turbulent flows around NACA0012 airfoil. For the computation of flow fields, a large-eddy simulation (LES) with the dynamic Smagorinsky subgrid scale (SGS) model and the cubic interpolated pseudo particle (CIP)-combined unified numerical procedure method were conducted. The reproduced turbulent flow around NACA0012 airfoil was in good agreement with the experimental data. For the estimation of acoustic fields, our acoustic model and classical sound source models, such as Lighthill and Powell, were performed using our LES database. The investigation suggested that the derived material derivative of the velocity divergence plays a dominant role as sound source. The distribution of the sources in our acoustic model was consistent with that of the classical sound source models. The sound pressure level (SPL) predicted based on the above-mentioned LES and our newly derived acoustic model was in reasonable agreement with the experimental data. The influence of the increase of Mach number on the acoustic field was investigated. Our acoustic source model was verified to be capable of treating the influence of Mach numbers on the acoustic field.

Numerical study on noise reduction of wind turbine blade vortex generator

At present, wind power is widely used, especially in near-residential areas, and blade noise has become an important factor affecting the installation and operation of the unit. Vortex Generator is a new technology that has been used by wind turbine blade manufacturers in recent years. At present, there are few studies on the changes of blade aerodynamic noise after the installation of vortex generators in China. In order to study the influence of vortex generators on aerodynamic noise, the flow field is simulated by numerical calculation method before and after the blade is installed with vortex generators. The visualization results are output and compared, and the parameters such as vorticity and pressure are analyzed. Secondly, based on the detailed parameters of the flow field, FW-H equation is used to calculate the sound source propagation, and the sound pressure level spectrum of the blade before and after the vortex generators added is obtained. The research shows that the vorticity increases in the vicinity of vortex generators and the downstream region, which promotes the mass and energy exchange between the upper fluid and fluid in the boundary layer, so the boundary layer separation is delayed, and the wake vortex subsides. The aerodynamic noise is low frequency noise, and the addition of vortex generators can significantly reduce the aerodynamic noise of the blade.

Tensile behaviour of hybrid and non-hybrid polymer composite specimens at elevated temperatures

Fiber Reinforced Polymer (FRP) composites are used extensively in aerospace, marine and civil engineering. High stiffness-to-weight and high strength-to-weight ratios make these materials suitable for modern wind turbine blade manufacturing industries. In the present study, glass, carbon and glass-carbon composite materials are studied to determine their tensile properties at elevated temperatures as this is an important design consideration for wind turbines operating in warm climates. Specimens were tested in a range of temperatures to investigate thermal effects on their mechanical, thermal and failure behaviors.Experimental and FEA results show that tensile strength and heat flow of specimens decrease with increasing temperatures. Hybridization of two materials changes failure mode behaviors. Tensile strength test data was analyzed using chi-square goodness of fit statistical model. Results were correlated by using linear regression analysis. Normal, lognormal and 2-parameter Weibull statistical approaches were used to quantify the degree of variability in tensile strength of specimens.

Manufacturing and Flexural Characterization of Infusion-Reacted Thermoplastic Wind Turbine Blade Subcomponents

Reactive thermoplastics are advantageous for wind turbine blades because they are recyclable at end of life, have reduced manufacturing costs, and enable thermal joining and shaping. However, there are challenges with manufacturing wind components from these new materials. This work outlines the development of manufacturing processes for a thick glass fiber–reinforced acrylic thermoplastic resin wind turbine blade spar cap, with consideration given to effects of the exothermic curing reaction on thick composite parts. Comparative elastic properties of these infusible thermoplastic materials with epoxy thermoset materials, as well as thermoplastic coupon components, are also included. Based on the results of this study it is concluded that the thermoplastic resin system is a viable candidate for the manufacturing of wind turbine blades using vacuum-assisted resin transfer molding. Significant gains in energy savings are realized avoiding heated molds, ability for recycling, and providing an opportunity for utilizing thermal welding.

Evaluation of Polymer Matrix Composite Waste Recycling Methods

Abstract Polymer-based matrix composite materials are in high demand in many different fields: aeronautics, pressure vessel manufacturing, wind turbine blade manufacturing, and others. Due to the great mechanical properties of fiber reinforced plastics, it is a desirable material for various applications, but at the same time its heterogenic structure makes the composite waste hard to recycle. This paper focuses on different fiber reinforced plastics (FRP) waste recycling methods and their comparison by carrying out literature review and using multi-criteria decision making analysis (MCDA). Four polymer matrix composite waste recycling methods are compared to calculate which one has the best sustainability performance based on the chosen criteria. Analytical Hierarchy Process and TOPSIS are applied for criteria weighing and method comparison. Sensitivity analysis is used to evaluate the obtained results. It is concluded that more studies concerning different FRP waste recycling method sustainability performance need to be done, to derive more data, that would make MCDA more reliable and also other FRP waste recycling methods could be compared. Another conclusion is that different methods have different strengths which makes it hard to compare them. While FRP waste recycling is getting more broadly used, there still is a lot of work to establish wide spread effective system of FRP waste recycling that is both economically viable and gives the best results concerning recycled material quality.

Theoretical study on the efficiency of utilization of nanoclay-CFRP composite materials in the root area of wind turbine blades

In this study, theoretical calculations were performed to determine the most efficient utilization of nanoclays added as reinforcement for CFRP composite materials used for wind turbine blade manufacture. Four different V39 blade models were created, and numerical simulations by FEA were performed. Glass Fibre Reinforced Polymers (GFRP), whole model made of Carbon Fibre Reinforced Polymers/nanoclay (2%) (CFRPN2), Hybrid Glass and Carbon/nanoclay (2%) (HGCN2) and Hybrid Glass and Carbon/nanoclay (5%) (HGCN5). The targeted part was the joining zone between the root and the blade. The most important finding to emerge from this study is that the modest addition of nanoclay (2%) with carbon fiber reinforced polymer leads to a significant stiffer blade, with a minimal deflection, about 70% lower than GFRP. Furthermore, the HGCN2 model is considered to be safer as it has a lower stress concentration than others (52.84 kN/m2). It can be considered that the probability of failure of the entire root area will be decreased if nanoclay-CFRP hybrid blades are used, yielding higher durability and lower overall costs. These findings contribute to decisions related to materials selection, structural, aerodynamic design and layup schedule choice.

Incorporation of glass fibre fabrics waste into geopolymer matrices: An eco-friendly solution for off-cuts coming from wind turbine blade production

In this investigation, an innovative and sustainable solution for glass fibre off-cuts is proposed. For the first time, glass fibre fabrics (non-woven mat) produced during wind turbine blade manufacture were used to produce reinforced inorganic polymer composites. The influence of fabric amount on the composites’ microstructure, water absorption, strength and apparent density was investigated. Results show that the fabrics exhibited an impressive flexural strength gain (up to 144%) at the 28th day, when compared to the non-reinforced geopolymer, while simultaneously increasing the composites’ ductility. This feature may extend the application range of such geopolymers. Moreover, the fabric prevents the complete collapse of the composites upon failure, while the matrix alone fails catastrophically under load.

Structural design of a multi-megawatt wind turbine blade with ONE SHOT BLADE® Technology

This paper presents the ONE SHOT BLADE® technology introduced in the wind turbine blade manufacturing process in order to reduce the time, and hence the costs required to build the blade. A comparison with respect to the standard process is also highlighted. The aim of this study is to optimize the structural configuration of a 50m length blade, built with this innovative manufacturing technique, providing a feasible design according to the international standard requirements.

Investigation of modal analysis of new materials for wind turbine blade

The aim of this study is the search for new material for the manufacture of wind turbine blades in order to improve its performance and to reduce its cost. A composite material based on hemp natural fibres is studied. A numerical simulation using the finite element method is developed and a comparison of the performances of the new material with the usual composite of carbon fibres and glass is performed. The simulation allows us to calculate the proper values and the Eigenmodes of a wind turbine blade in the rotation. The results showed that the epoxy matrix allows to reduce the weight of composite hemp/epoxy relative to other matrix. It is almost 4.6% lighter than hemp/phenolic and 1.9% that hemp/polyester, so the blades hemp/epoxy has several advantages over the blades hemp/phenolic or over the blades hemp/polyester: this new material is characterised by lower weight and lower cost and has better mechanical features.
 
 Keywords: Eigenmode, proper values, new material, blade, rotation.

Preparation and mechanical characterization of flax and glass fiber reinforced polyester hybrid composite laminate by hand lay-up method

Composites are the leading materials used in industries like aerospace, shipbuilding, automobile and also in the field of renewable energy in wind turbine blade manufacturing. Amongst that fiber reinforced composites gains more importance due to its high strength and stiffness value, most of the fiber reinforced composites incorporate glass fiber as reinforcement which is a high density material and causing many environmental problems in disposal after end use. This diverts the attention of researchers towards natural fiber as a reinforcing material for structural applications which is already a highly used member in many non-structural applications. The objective of this work is hybridization of natural fiber and synthetic fiber, the natural fiber used is flax and the synthetic fiber is glass fiber along with polyester resin. The laminates are prepared with different volume of flax and glass fiber and their mechanical properties like tensile strength, impact strength, flexural strength and water absorption nature are tested. The tests are carried out on standard ASTM sized samples the results show that the hybrid composite is showing equally good performance to conventional glass fiber composite and overall better performance than the mono natural Fiber composite.

Effects of defects in composite wind turbine blades – Part 1: Characterization and mechanical testing

Abstract. The Montana State University Composite Material Technologies Research Group performed a study to ascertain the effects of defects that often result from the manufacture of composite wind turbine blades. The first step in this multiyear study was to systematically quantify and enter these defects into a database before embedding similar defects into manufactured coupons. Through the Sandia National Laboratories Blade Reliability Collaborative (BRC), it was determined that key defects to investigate were fiber waves and porosity. An inspection of failed commercial-scale wind turbine blades yielded metrics that utilized specific parameters to physically characterize a defect. Methods to easily and consistently discretize, measure, and assess these defects based on the identified parameters were established to allow for statistical analysis. Data relating flaw parameters to frequencies of occurrence were analyzed and found to fit within standard distributions. Additionally, mechanical testing of coupons with flaws based on these physical characterization data was performed to understand effects of these defects. Representative blade materials and manufacturing methods were utilized and both material properties and damage progression were measured. It was observed that flaw parameters directly affected the mechanical response. While the data gathered in this first step are widely useful, it was also intended for use as a foundation for the rest of the study, to perform probabilistic analysis and comparative analysis of progressive damage models.

Investigating the measurement of offshore wind turbine blades using coherent laser radar

Large-scale offshore wind turbine blades need careful dimensional inspection at the production stage. This paper aims to establish an accurate measurement technique using Coherent Laser Radar technology combined with B-Spline point generation and alignment. Through varying the Degrees of Freedom (DoF), used for data point transformation, within the Spatial Analyser software package, erroneous inspection results generated by unconstrained blade flexing can be eradicated. The paper concludes that implementing a single B-Spline point generation and alignment method, whilst allowing transformation with DoF in X, Y and Rz, provides confidence to wind turbine blade manufacturers that inspection data is accurate. The experimental procedure described in this paper can also be applied to the precision inspection of other large-scale non-rigid, unconstrained objects. This paper aims to establish an accurate measurement technique using Laser Radar for wind turbine blade inspection.Degrees of Freedom are used for data point transformation.B-Spline curves are constructed to compare with the complex curved surface profiles of the CAD blade.Experimental procedures and data transformations are proposed for future industrial implementation.

Synthesis, fabrication and mechanical characterization of reinforced epoxy and polypropylene composites for wind turbine blades

Failure of wind turbine blades usually originates from manufacturing defects or in-service defects. In this study, materials selection for manufacturing of wind turbine blades was carried out based on the mechanical and physical results obtained using the Cambridge Engineering Selector program. Thermoplastic and thermosetting composites were synthesized and processed using injection molding and vacuum assisted resin infusion techniques, respectively. Operating conditions (vacuum pressure and temperature) were optimized. The manufactured samples were tested and evaluated using destructive tests. Tensile and fatigue tests were carried out. Polypropylene random discontinuous glass fiber composites were synthesized and processed using mold injection technique. Epoxy-carbon, glass and carbon/Kevlar hybrid fiber composites were manufactured using vacuum assisted resin infusion technique. Surface morphology was characterized using scanning electron microscope analysis. Tensile strength and fatigue resistance were significantly improved by the presence of E-glass fiber (30 wt%) in polypropylene-glass fiber composites. The experimental results were compared with the Cambridge Engineering selector software database. Epoxy-carbon (carbon fiber fraction is 0.61) and carbon/Kevlar hybrid (fibers fraction is 0.6) composites showed superior mechanical properties. Epoxy/carbon composite can withstand stresses up to 1390 MPa at 106 cycles.

Mechanical evaluation of repair resins for fiber-glass wind turbine blades

This paper contains details of mechanical testing of double cantilever beam composite specimens comprising a vacuum-assisted resin transfer molding–infused parent plate and a hand laid-up upper plate simulating a typical blade repair. The testing was carried out as part of an effort to optimize a new repair resin for a wind turbine blade manufacturing company. A number of commercial suppliers were contacted and nine resins with different formulations were selected for screening. Out of these, six were shortlisted for initial testing which was carried out in accordance with ASTM D 5528 (Test Method for Mode I interlaminar fracture toughness of unidirectional fiber-reinforced polymer matrix composites) using double cantilever beam specimens. The fracture toughness values obtained from testing these repair resin candidates were compared to values obtained from the repair resin currently being used and also to those of the main blade resin. The top three repair resin candidates were identified from the double cantilever beam testing.

Research on Manufacturing Logistics with Applied Technology Based on Logistic Distribution Probability Function and Elman Neural Network of Wind Power

This article focuses on the probability distribution of wind power fluctuations and prediction problems, on this basis, putting forward new ideas for wind blade manufacturing process. Depending on that wind power has the characteristics of volatility, this article finds the probability distribution of wind power fluctuations in Logistic function is the best fit between the location - scale function, Logistic function, Extreme value function, and Normal function, Then, this article utilize the Elman neural network prediction model to forecast the wind power in the coming period of time, good results are obtained. Finally, we use new ideas in the manufacture of wind turbine blades with whole hollow, pitch type, carbon fiber as a reinforcing material.

Design and Manufacturing of Wind Turbine Blades of Low Capacity Using CAD/CAM Techniques and Composite Materials

This paper proposes a methodology for design and manufacturing of wind turbine blades of low capacity with CAD (Computer Aided Design)/ CAM (Computer Aided Manufacturing) techniques and composite materials. The design of the blades was performed with help of specialized software, one of them developed in the author's institution (TIMEO®). The manufacturing of the blades model was executed in a machining center of three axes CNC, DYNA MYTE DM-4800. The final manufacture of composite materials was performed.The wind energy is an indirect form of the solar energy, since they are the temperature differences and the pressure-induced in the atmosphere by absorbing solar radiation, which set in motion the winds. The rotor mission in a wind turbine is transforming this kinetic energy of wind to mechanic energy. In this paper the design of the blades is based on the blade element moment theory. For the design and manufacturing CAD/CAM was developed a general methodology. In manufacturing of the blade was necessary to manufacture a false bed, which was used as a virtual axis, this is because the milling machine where this was manufactured only has three axes.The mechanical efficiency of a wind turbine depends on other factors airfoil blade, since the aerodynamic forces that occur in this provides the torque necessary for rotating the electric generator. In this sense, obtaining highly accurate airfoil geometries helps to improve the efficiency of the wind machine.Blades were manufactured of length 75.5cm, for a 600 watts wind turbine power, the design parameters were based on the environmental conditions of the coast of Michoacán, Mexico. The machining of the blades model are made from wood by mechanical milling, which is a manufacturing process for metal removal performed by the motion of a rotating cutting tool called milling cutter. The final manufacture of fiberglass performed and in which an internal structure is proposed to provide the parameters necessary rigidity and flexibility.The results obtained show that is feasible the manufacture of this type of mechanical elements through these techniques. We show that the precise control of geometry directly impacts in the aerodynamic efficiency of wind machine.

Non-Destructive Investigation of Glass Fiber Reinforced Composites via Magnetic Resonance Imaging

Glass fibre reinforced composites (GFRC), used in the manufacture of wind turbine blades, can suffer unpredictable, post-manufacturing, in-situ structural failure. The economic cost of remediation of such blade failures is extremely high, both on land and offshore. We suggest using zero-time-to-echo (ZTE) magnetic resonance imaging (MRI) as a method for characterising glass fibre reinforced composites. Initially, we demonstrate that carbon-13 Nuclear Magnetic Resonance (NMR) spectra acquired at 800MHz provide finger-print like information and that there is sufficient hydrogen-1 NMR signal available to conduct MRI. This work explores the efficacy of using zero timetoecho (ZTE) magnetic resonance imaging (MRI) to detect the rapidly decaying Hydrogen-1 (1H) NMR signal from a representative sample. A 400MHz surface resonator was developed made of a 20mm diameter loop formed with 1.5mm thick silver wire and designed with variable tuning and matching in order to investigate the 1H-MRI signal at 9.4T static magnetic field strength. The thickness of the GFRC was determined from the MRI data to be 3.51±0.28mm while the physical measurement using a caliper device resulted in a measurement of 3.45mm. Hence, a high spatial resolution accuracy is provided by ZTE MRI. Very short T2* (<20μs) of the material led to stronger blurring artefacts for the blade material compared to heat shrink used for insulating the silver wire of the detector. 1H images of the blade material were acquired demonstrating that ZTE is a suitable technique for acquiring image data from glass fibre materials. Work is on-going in studying the relaxation time parameters and chemical frequency shifts for materials with and without structural weaknesses in order to improve the predictive power of the technique. In conclusion, ZTE-MRI can provide useful information about the mechanical properties of glass fibre reinforced composites.

Detecting salt deposition on a wind turbine blade using laser induced breakdown spectroscopy technique

The study of pollution performance on a wind turbine blade due to lightning is important, as it can cause major damage to wind turbine blades. In the present work, optical emission spectroscopy (OES) technique is used to understand the influence of pollutant deposited on a wind turbine blade in an off-shore environment. A methodical experimental study was carried out by adopting IEC 60507 standards, and it was observed that the lightning discharge propagates at the interface between the pollutant and the glass fiber reinforced plastic (Material used in manufacturing of wind turbine blades). In addition, as a diagnostic condition monitoring technique, laser-induced breakdown spectroscopy (LIBS) is proposed and demonstrated to rank the severity of pollutant on the wind turbine blades from a remote area. Optical emission spectra observed during surface discharge process induced by lightning impulse voltage is in agreement with the spectra observed during LIBS.