Composite Blades Research Articles

Performance and Damage Study of Composite Rotor Blades under Impact.

A military helicopter is easily attacked by bullets in a battlefield environment. The composite blade is the main lifting surface and control surface of the helicopter. Its ballistic performance directly determines the vulnerability and survivability of the helicopter in the battlefield environment. To study the ballistic performance of the composite helicopter blade, the damage characteristics of the impacted composite rotor blade are obtained by experiments. A numerical simulation model is established by applying Abaqus software to predict the blade ballistic damage. The three-dimensional progressive damage failure model is used to analyze the ballistic damage under the experimental conditions. The effectiveness and accuracy of the numerical simulation model are verified through a comparison with the experimental results. The ballistic damage of composite blades under three experimental conditions was investigated. The results show that the ballistic damage type of composite blade mainly includes delamination, fiber breakage, and foam collapse. The damage to the composite material at the position of bullet incidence is mainly local shear fracture, while the damage to the composite material at the exit position is mainly fiber tensile fracture. The ballistic damage size of the composite blade is closely related to the ballistic position, incident angle, and structure characteristics along the ballistic path. The larger the incident angle, the smaller the ballistic damage size of the blade. The greater the structural stiffness of the structure near the exit, the greater the damage size of the exit. The numerical simulation model presented in this paper can provide a reference for research on the ballistic performance of composite helicopter blades.

DLFSI: A deep learning static fluid-structure interaction model for hydrodynamic-structural optimization of composite tidal turbine blade

Horizontal axis tidal turbines (HATT) conversion of ocean tidal waves into electricity represents a promising source of clean and sustainable energy. However, the widespread adoption of these turbines has been hindered by persistent challenges, primarily stemming from the high costs associated with their construction and maintenance; and efficient conversion of tidal energy. Addressing these challenges is paramount for propelling tidal turbine technology and ensuring its economic viability. This study focuses on the efficient conversion of tidal energy into electricity by optimization of composite material turbine blades which is a complex problem that spans multiple physical domains, including hydrodynamics (the study of water flow) and structural mechanics (the study of material behavior under loads). To tackle these multifaceted challenges, we introduce an innovative DLFSI (Deep learning fluid-structure interaction) model which represents a groundbreaking approach to predict and optimize the hydrodynamic and structural performance of tidal turbine blades. DLFSI leverages the power of convolutional neural networks (CNN) to recognize intricate geometric features of turbine blades rapidly and accurately. By seamlessly integrating the blade element momentum (BEM) theory and finite element method (FEM), the DLFSI model facilitates comprehensive predictions of how composite blades will perform in real-world conditions. With this approach, we have achieved substantial improvements in critical performance metrics such as the power coefficient (a measure of energy conversion efficiency) and the maximum equivalent stress (a key indicator of structural integrity). The innovative DLFSI model presented in this study holds the potential for practical application within the realm of tidal turbine design and is poised to catalyze the sustainable progression of renewable energy technologies.

Investigation of the stress–strain state of a composite blade in ANSYS WorkBench

In this paper, the static strength of a UAV blade made of composite material was calculated. Composite materials have an advantage over traditional materials (metals and alloys) in the field of aviation - gain in weight, low sensitivity to damage, high rigidity, high mechanical characteristics. At the same time, the identification of vulnerabilities in a layered structure is a difficult task and in practice is solved with the help of destructive control. Composite materials available in the ANSYS materials library were used in the modeling: Epoxy Carbon Woven (230 Gpa) Prepreg woven carbon fiber in the form of a semi–finished prepreg impregnated with epoxy resin carbon fiber with Young's modulus E=230 GPa and Epoxy Carbon (230 Gpa) Prepreg is a unidirectional carbon fiber prepreg impregnated with epoxy resin with a Young's modulus E=230 GPa. Modern software products, such as ANSYS WorkBench, allow comprehensive investigation of the layered structure. Several variants of blade designs with different fillers as the median material were investigated. The forward and reverse destruction criteria based on the Tsai-Hill theory were used. The influence of gravity was not taken into account. It is shown that the developed blade design meets the requirements. Balsa wood, pine, aspen and polyurethane foam were chosen as the middle material of the blade. Pine and aspen wood were selected according to the criteria of their availability and having the lowest density. The materials library of the ANSYS WorkBench software package used does not have characteristics for all of them, so the characteristics of the selected materials (pines and aspens) were added manually. For modeling and calculations in the ANSYS WorkBench program, such characteristics as density, axial elastic modulus, Poisson's coefficients, shear modulus and tensile and compressive strength limits are required.

Strategic Quality Control Measures to Reduce Defects in Composite Wind Turbine Blades

Wind turbine blades are made from polymer composites to provide high specific stiffness, strength, and good fatigue performance. However, large composite structures are prone to manufacturing defects such as delamination and adhesive failure, which can lead to crack initiation and propagation under cyclic stresses. National renewable energy laboratory, USA statistics shows 26% fatigue failure modes are created by laminate and adhesive joint manufacturing errors. A range of manufacturing processes are used to construct wind turbine blades. Resin transfer infusion is one of the most frequently used methods in wind turbine blade manufacturing industry. This paper provides assessment on regular defects occurring in resin transfer infusion processes which lead to poor quality in wind turbine blade manufacture. The assessment is based on the existing literature and the know-how generated from manufacturing wind turbine blades. The effect of these defects for the structural failure of composite wind turbine blades is analysed. The final phase of the study provides manufacturing quality control measures which can be implemented to improve the composite wind turbine blade manufacturing process.

The Effect of Ply Waviness for the Fatigue Life of Composite Wind Turbine Blades

Wind turbine blade failure is one of the most prominent types of damage occurring in operating wind turbine systems. Glass fibre materials are mainly used for producing wind turbine blades and they consist of large tows, stitched fibres, which are prone to generate imperfections such as ply waviness. The primary objective of this research was to evaluate the effect of ply waviness on fatigue life of typical composites used in wind turbine blades. This study involves two main areas: Finite elements analysis (FEA) and experimental testing. The Finite element analysis was carried out using the commercial code from ESI group. The experimental work was carried out by manufacturing specimens from glass fibre with regular waviness and testing for static and fatigue failure. The tensile static test data was used to identify the effect of ply waviness for failure strength. Cycles to failure (S-N) curves were developed for two different wave profiles based on fatigue testing data. The long term aim of this ongoing research is to improve current fatigue life estimation methods applicable to composite wind turbine blades.

Glass Fibre Composites Recycling Using the Fluidised Bed: A Comparative Study into the Carbon Footprint in the UK

The UK has no established process for recycling waste glass fibre-reinforced thermosets that are widely used within wind blade structures. Consequently, these materials are typically disposed of in landfills or undergo energy recovery in waste facilities. This study investigates the carbon footprint of the fluidised bed process for recycling glass fibre composite waste, considering the present and future scenarios of composite waste management in the UK. The impact was compared to conventional disposal routes and other prominent recycling technologies, such as cement kiln co-processing and mechanical recycling, by developing energy and material flow models for each waste treatment strategy. Variables, such as the type of waste, the quantity of recycling facilities in the UK, and waste haulage distance, were examined to inform the lowest impact deployment of recycling technologies. Cement kiln co-processing, mechanical, and fluidised bed recycling technologies reduced the global warming potential of processing wind blade waste compared with conventional disposal routes, with impacts of −0.25, −1.25, and −0.57 kg CO2e/kg GRP waste, respectively. Mechanical recycling had the lowest global warming potential resulting from low greenhouse gas emissions associated with the process itself and potentially high offsets by replacing glass fibre in the production of moulding compound. Composite wind turbine blade waste was found to be a particularly promising feedstock for the fluidised bed process due to relatively low resin content diminishing direct greenhouse gas emissions during thermal decomposition, as well as high material recovery offsets due to the high glass fibre content of this waste stream.

Vibration characteristics of pre-twisted rotating Ti-SiC composite airfoil blade

In this paper, a pre-twisted blade model is established based on the FSDT (first-order shear deformation theory), where the Ti-SiC fiber reinforced composite and NACA 4-digit airfoil are innovatively proposed. Rayleigh-Ritz method is utilized to deduce the pre-twisted blade natural frequencies and mode shapes where the exponential polynomials satisfying the cantilever boundary conditions are taken as admissible functions. Comparing with the existing literature, the precision of the model and the method is verified. The material properties of Ti-SiC fiber reinforced composites are calculated by the M-T (Mori-Tanaka) method and FE (Finite Element) method to guarantee the reliability of the calculation method. In addition, the parameters affecting blade vibration, such as rotating speed and aspect ratio, are studied in detail. The research findings indicate that the addition of SiC fibers enhances the properties of the composite blade, and then improves the frequency of the rotating blade. Additionally, the pre-twisted angle, rotating speed, aspect ratio and blade shape significantly affect the natural frequency of Ti-SiC composite airfoil blade. The well-established model accurately predicts the dynamic behaviors of the rotating blade, which has certain guiding value for the optimization of blade material and geometric size.

Manufacturing Process of Helicopter Tail Rotor Blades from Composite Materials Using 3D-Printed Moulds

Conventional processes require a mould for the manufacture of each test product, which often results in high costs but is ideal for large series of products. In contrast, for prototypes, additive manufacturing processes are a suitable low-cost time-saving alternative. The primary objective of this study is to investigate the capabilities of 3D-printed tooling in a real-life scenario for composite blades with low production numbers and prototypes in order to allow development and production costs to decrease and to also reduce lead times in the early phases of new projects. The 3D printing process is economically advantageous in terms of production costs for the composite blade mould, reducing the cost three times compared to the conventional manufacturing process. To obtain the composite helicopter blade, the following phases were carried out: the starting design of the mould, 3D printing and assembly of the mould sections, and blade manufacturing. The economic analysis of the two mould manufacturing methods shows an approximately equal ratio between the manufacturing costs of the 3D-printed mould and the manufacturing costs of the blade, whereas in the conventional processes, the costs for mould manufacturing represent 75% of the total cost and the rest (25%) of the cost is spent on blade manufacturing.

Monitoring fatigue delamination growth in a wind turbine blade using passive thermography and acoustic emission

Damage monitoring is an essential step to understand fatigue damage growth in composite wind turbine blades and for reliable lifetime prediction. The current study is an experimental investigation of fatigue delamination induced by an intentionally embedded defect in the spar cap of a 31 m wind turbine blade. A constant cyclic flap-wise bending was applied to the blade for 320,000 cycles. Delamination growth is identified and measured by visual inspection, acoustic emission (AE), and infrared thermography of the blade surface. It was observed that the area of delaminated regions grew faster during the early cycles, then their growth rates decreased, and the interlayer cracks reached stable growth. The experiment shows fatigue delamination develops gradually in the spar cap and allows monitoring of the damage before reaching a critical stage. The ability of AE and thermography methods to detect subsurface damage is demonstrated by the identification of steady delamination growth during cyclic load. Damage localization by both methods is in good agreement with the delamination location. Most acoustic activities are spotted in the boundaries of delaminated regions, and the position of a significant number of acoustic activities with the highest energy content correlates with the location of delamination crack fronts. It is shown that the surface temperature distribution contour indicates the shape of the largest delaminated region, and the growth of the hot region area correlates with damage propagation. However, multiple delaminations through the thickness cannot be discriminated from the thermal images.

Nonlinear dynamics of graphene-reinforced aluminum matrix composite aero-engine blade in thermal environment

This paper analyzes the nonlinear dynamic behaviors of the graphene-reinforced aluminum-based aero-engine blade under the primary resonance using the amplitude-frequency response curves, bifurcation diagram, Lyapunov exponent and Poincaré map. The lateral aerodynamic load, longitudinal aerodynamic load, centrifugal force and temperature are investigated for the graphene-reinforced aluminum-based aero-engine blade. Three kinds of configurations for the functionally graphene-reinforced gradient are considered. The effective Young's modulus of the composite material is given by Halpin-Tsai mode. The rule of the mixture gives other material properties. The results demonstrate that the bifurcation diagrams of the modal amplitude for the blade with the lateral aerodynamic load, longitudinal aerodynamic load and temperature have the periodic-chaos dynamic evolution process under the disturbance of the engine rotation speed. When the disturbance amplitude reaches a specific value, a new round of the periodic-chaos dynamic evolution will be continued. The results also clearly indicate that the aero-engine blade has the rich and complex nonlinear dynamic behaviors which include the hyperchaos, chaos, almost periodic, typical period-doubling bifurcation and anti-period-doubling bifurcation vibrations. This research is more helpful for the engineers to understand the nonlinear dynamic behavior of the blade.

3D multiscale dynamic analysis of offshore wind turbine blade under fully coupled loads

Wind turbine blades are typically sophisticated structures with complex geometry and composite layup. The realistic loads acting on blades serviced in harsh offshore environments are fully coupled dynamic loads involving wind, wave, current, servo-control, gravity and other inertial loads. This work presents an easy-to-implement methodology for the time-domain detailed analysis of three-dimensional (3D) blade structure, by combining fully coupled dynamic simulator and general finite element program. As a practical example subjected to multiple marine environmental loadings, one of the rotating composite blades atop a 5-Megawatt (MW) monopile-supported offshore wind turbine (OWT) in soft clay is used for verifying this method step by step, and the effect of rotation and foundation flexibility on blade behaviours is explored. Good agreement between OpenFAST and proposed method in tip deflections and root reaction loads is visible from validation results, and the recommendations on how to further improve this method in future iterations are made. Subsequently, based on stress-time history of blade composite layups, time-domain 3D multiscale analysis including the failure evaluation for layers in outer shell and shear webs using Tsai-Wu strength criteria, as well as the fatigue damage assessment of carbon spar caps was performed.

Long term co-application of biochar and fertilizer could increase soybean yield under continuous cropping: insights from photosynthetic physiology.

Photosynthesis is the key to crop yield. The effect of biochar on photosynthetic physiology and soybean yield under continuous cropping is unclear. We conducted a long-term field experiment to investigate the effects of co-application of biochar and fertilizer (BCAF) on these parameters. Five treatments were established: F2 (fertilizer), B1F1 (3 t hm-2 biochar plus fertilizer), B1F2 (3 t hm-2 biochar plus reduced fertilizer), B2F1 (6 t hm-2 biochar plus fertilizer), and B2F2 (6 t hm-2 biochar plus reduced fertilizer). BCAF increased chlorophyll and leaf area, enhancing soybean photosynthesis. The net photosynthetic rate (Pn ), transpiration rate (Tr ), stomatal conductance (Gs ), water use efficiency (WUE) and intercellular carbon dioxide (CO2 ) concentration (Ci ) were enhanced by BCAF. In addition, BCAF improved soybean photosystem II (PSII) photosynthetic performance, driving force, potential photochemical efficiency (Fv /F0 ), and quantum yield of electron transfer (φE0 ). Furthermore, BCAF enhanced the accumulation of photosynthetic products, such as soluble proteins, soluble sugars and sucrose content, resulting in higher leaf dry weight. Consequently, BCAF increased the soybean yield, with the highest increase of 41.54% in B2F1. The correlation analysis revealed positive relationships between soybean yield and chlorophyll, leaf area, maximal quantum yield of PSII (Fv /Fm ), electron transport flux per cross-section at t = 0 (ET0 /CS0 ), trapped energy flux per cross-section at t = 0 (TR0 /CS0 ), composite blade driving force (DFTotal ), and leaf dry weight. We demonstrated that long-term BCAF enhances soybean photosynthesis under continuous planting, reduces fertilizer use and increases yield. This study reveals a novel way and theory to sustainably increase soybean productivity. © 2023 Society of Chemical Industry.

Spar Cap/Shear Web Debonding Under Fatigue Loading Studied On The DTU 12.6m Wind Turbine Blade

Understanding fatigue damage initiation and propagation of composite wind turbine blades is an essential step towards the design of reliable prognostic and health management systems (PHM) and to improve lifetime predictions. This study presents a numerical investigation of the debonding process in the spar cap/shear web region of a full-scale composite wind turbine blade under fatigue loading and presents the manufacturing approach for creating initial debondings. For this purpose, numerical simulations have been performed to design and specify the size and locations of artificial defects to provoke steady, controllable damage growth in the adhesive bondline between the rear shear web and cap region of the DTU 12.6m wind turbine blade under fatigue loading. Subsequently, these artificial defects are embedded into the manufacturing process of the composite wind turbine blade with the help of slip foils and partially perforated slip foils to create regions with no bonding, 30% and 50% bonding of the contact surfaces of the adhesive joint, respectively.The numerical predictions as well as the manufactured and instrumented blade sets the framework to subsequently execute experimental tests of damage growth in the adhesive joint of the bondline in order to compare numerical and experimental data. The experimental demonstration will allow to better understand the complexity of damage growth of composite structures under fatigue loading and the necessity of accurate numerical prediction tools for reliable prognostic health management systems.

Modal Parameter Identification and Damage Localization of Composite Helicopter Rotor Blades Based on AR/PR Identification

The structural characteristics and application background of helicopters determine that the primary dynamic components work in environments with high cyclic amplitude and low‐stress vibration fatigue load. As the most critical structural system of helicopters, structural health monitoring of the rotor blades is necessary to avoid fatigue damage under working conditions. Modal parameters, as functions of the physical properties of structural systems, change when there is damage or internal defects (the mass, stiffness, and damping of the structure will change). This article completes the identification of modal parameters of composite rotor blades under working conditions based on operational modal analysis (OMA). Specifically, using the AR/PR (autoregressive/polyreference) time‐domain identification method, experiments are designed to identify the modal parameters (natural frequency, modal damping ratio, and mode shape) of composite rotor blades based on acceleration and strain signals. The results of the identification of modal parameters are verified through finite element simulation and modal measurement experiments. In addition, the application of OMA for the location of composite rotor blade damage is also studied.

Mapping damages from inspection images to 3D digital twins of large‐scale structures

AbstractThis study develops a methodology to create detailed visual Digital Twins of large‐scale structures with their realistic damages detected from visual inspection or nondestructive testing. The methodology is demonstrated with a transition piece of an offshore wind turbine and a composite rotor blade, with surface paint damage and subsurface delamination damage, respectively. Artificial Intelligence and color threshold segmentation are used to classify and localize damages from optical images taken by drones. These damages are digitalized and mapped to a 3D geometry reconstruction of the large‐scale structure or a CAD model of the structure. To map the images from 2D to 3D, metadata information is combined with the geo placement of the large‐scale structure's 3D model. The 3D model can here both be a CAD model of the structure or a 3D reconstruction based on photogrammetry. After mapping the damage, the Digital Twin gives an accurate representation of the structure. The location, shape, and size of the damage are visible on the Digital Twin. The demonstrated methodology can be applied to industrial sectors such as wind energy, the oil and gas industry, marine and aerospace to facilitate asset management.

Identification of Damage in a Wind Turbine Blade Using Mechanical Measurements and Artificial Neural Networks

Due to the stochastic nature of environmental loadings, a lot of interest is paid in the discovery of possible damages of the involved equipment in modern industry. In wind turbines’ blades, the development of a smart structural health monitoring system is essential. In this paper, a large-scale composite wind turbine blade model is designed and used for the detection of several damage scenarios. The process is mainly based on the development of monitoring techniques which exploit the capabilities of artificial neural networks. These techniques can provide the exact position of possible damages, under given external loading scenarios. Moreover, the use of such methods decreases significantly the need of external intervention and at the same time it increases the accuracy of the whole approach. The above processes are simulated using the finite element method. The goal is to develop a neural network which realizes the correlation of measurements with damage patterns. The goal is focused on the solution of inverse problems involving elastically deformable structures, based on remote mechanical measurements. The correlation between measurements and damages, which is much more complicated in comparison to image analysis, is studied by means of neural networks.

Damage Modelling and Analysis of Composite Blade for Wind Turbine

A study was conducted on the change in mechanical properties due to void, one of the fabrication defects of composite materials for wind turbine blades. The study was conducted based on glass fiber fabric, which is mainly applied to wind turbine blades, and the material properties were predicted by simulating random defects with micro and meso modeling of the composite material with void. The basic properties due to void were predicted through the homogenization method, and the failure properties were obtained through progressive failure analysis by applying virtual coupons according to ASTM D3090 and ASTM D6641. The currently widely used Mori-Tanaka method was used for mean field homogenization, the Hashin theory was used for failure conditions, and the Matzenmiller-Lubliner-Taylor method was used for progressive failure.

Wind turbine blades with hybrid fiber composite: Tensile properties and numerical verification

Wind turbine blades are the main component of wind turbines to capture effective wind energy, and require good quality and reliable performance. Therefore, the manufacturing cost of wind turbine blades is much higher than that of other components of wind turbines. The blade is a slender elastomer prone to vibration. The wind turbine vibration always arises in the blade instability. At the same time, the blade is also a typical aerodynamic component. In the process of rotation, it will not only produce mechanical vibration but also bear aerodynamic force. In this paper, the mechanical properties and modal numerical simulation analysis of composite blades with different hybrid ratios of carbon fiber and glass fiber are analyzed, it is found that with the increase of carbon fiber content, the mechanical properties of the blade gradually increase, and the torsional vibration resistance of the blade become stronger. Therefore, the wind turbine blades of hybrid fiber composites have a longer service life, which can reduce material wastage and help protect the environment.

Modelling and analysis of jute fiber reinforced epoxy composite in the development of wind blade for low intensity winds

Natural fibers show an increasing potential as reinforcement of polymeric composites, representing a promising concurrent to glass and carbon fibers extensively used in the construction of wind turbine blades synthetic fibers recyclability/disposability and high production energy cost have already been discussed in the main turbine producing centres. In particular, the development of wind turbines for low wind speed areas can increase the energy generation potential of regions not originally eligible for the installation of large turbines. This study proposes the evaluation of the use of jute fiber (Corchorus capsularis) reinforced epoxy composite in the construction of S1210 airfoil profile, of a small-scale wind turbine for low wind speed regions, considering the structural parameters, developed incorporating the Classical Laminate Theory (CLT) and Extended Bredt-Batho Shear Flow Theory (EBSFT).In order to raise the elastic properties and enable the use of the failure criteria, the composite blades were characterized according to ASTM standards. The mechanical properties surveyed, together with the elastic parameters of the cross section, torsional stiffness, axial stiffness, GJ 1873.6 N m2, EI 9.47 × 104 N m2, and flexural rigidity, Ely 4.97 × 104 N m2, Elz 1.45 × 106 N m2, respectively, demonstrated the feasibility of using the jute fiber reinforced epoxy composite in the blade construction, evaluated according to the maximum tension failure criterion.

Comparative analysis of the dynamic characteristics of all-metal, composite and composite blades with the same profile, taking into account the influence of the connection of elements and aerodynamic loads

The paper presents a comparative analysis of the dynamic properties of the blades of one rotary machine which have the same airfoil shape, but are made of three different materials, namely aluminum alloy, a complex material combining aluminum alloy and steel, and a composite material which is unidirectional fiberglass. In the case of an all-metal blade, its airfoil and root are made of aluminum alloy. In the case of complex blade airfoil material, the root is made of steel which is also a component of the airfoil material. In the case of a composite blade, the root is steel and is connected at the root section to its composite airfoil. The main attention when comparing models of the mechanical behavior of three types of blades is paid to the influence of the connection of complex and composite elements with the root on the dynamic characteristics of the blade as a whole which is achieved by considering the contact interactions of the elements under the action of centrifugal and aerodynamic loads and the subsequent transfer of the prestressed state of the blades to the modal analysis for determination of the dynamic characteristics of samples and their comparison. In order to correctly display the fixation of elements in the fan impeller in the case of an aluminum blade, the sector of cyclic symmetry of the rotor is considered which makes it possible to draw a conclusion about the possibility of further separate consideration of the blade for determination of its dynamic characteristics due to the much greater stiffness of the connection of the blade with the impeller in comparison with stiffness of the blade airfoil, and to generalize this conclusion in the case of a complex blade by considering a steel root with an aluminum profile with rigid clamping of the model on the contact shelves of the root, and in the case of a composite blade by considering an airfoil with rigid clamping in the root section, where the fastening to the steel root of the blade takes place. The results of a comparative analysis of the dynamic behavior of three types of blades with the same airfoil shape are presented in the form of a study of the blade natural frequencies and mode shapes.