Materials and Manufacturing Techniques for Wind Turbine Blades

Wind Power Project Management 2012

Materials and Manufacturing Techniques for Wind Turbine Blades Wind Turbine Concepts and Applications Haseeb Ahmad [email protected]

Submitted to Dr. Bahri Uzunoglu

Högskolan på Gotland, Sweden

Wind Turbine Concepts and Applications

Project Summary

Project Title

Materials and Manufacturing Techniques for Wind Turbine Blades

Investigator

Haseeb Ahmad

This project describes the comparison between different materials and techniques used for wind turbine blade manufacturing. Blades are the integral part of wind power projects so the focus is on the characteristics of materials and manufacturing techniques for the blades. The objective is to provide basic information and understanding about the materials and manufacturing techniques for wind turbine blades. This document will cover the process methodology, advantages and disadvantages of different manufacturing techniques.

Key Words:

Wind Turbine Blades, Blade Geometry, Composite Materials, Manufacturing

Technique Characteristics.

2


Co C on n t en e ntt s

1.

Introduction

4

2.

Wind Turbine Blades

5

2.1 3.

3.1 3.2 3.3 3.4 3.4.1 3.4.2 3.5 3.5.1 3.5.2 3.6 4.

4.1 4.2 4.3 4.4 4.4.1 4.4.2 4.4.3 5.

Blade Geometry Wind Turbine Blade Materials

Wood Steel and Nickel Alloy Aluminum Fiber Glass fiber Carbon fiber Matrix materials Thermosetting Polymers Thermoplastic Polymers Composite materials Manufacturing Technologies

Wet hand lay up Filament winding Prepreg technology Resin Infusion Technology Resin Transfer Molding (RTM) Seeman Composite Resin Infusion Molding Process (SCRIMP) Resin Film Infusion (RFI) Conclusions

5 7

7 7 7 7 8 10 11 11 13 13 16

16 17 18 18 19 20 20 21

References References

3


1. Introduction Blades are one of the main components of wind turbines. They have shape like aero-plane propeller, and attached to the rotor hub. They posses almost the same aerodynamic and structural properties like aero plane wings. But there are some modifications which have to be made because the blades are used in a wind power generation system. The wind turbine blades (airfoils) convert the wind energy into mechanical energy of shaft through their rotation. In the modern era, where wind turbines are operated with different speeds, the strength of blades plays an important role in the success of wind power project because, they not only transform wind energy but also regulate the power production through their orientation. Wind turbines blades, during their normal operating cycle i.e. 20 years, pass through severe environmental conditions e.g. wide range of temperatures, hails, ultraviolet and bird collisions etc. They bear static and dynamic lift, drag and inertial loads so it is important to select those blades which can withstand these challenges otherwise they can face structural damages and fatigue related issues due to cyclic loading. These problems of fatigue could be resolved by improving the characteristics of materials for the blade manufacturing, production processes and modification in the design and configuration of the blades. It is of utmost importance that the blades should be highly rigid having low weight and must possess rotational inertia, and above all they can resist wear and fatigue. If we look into the history of wind turbines, the early wind turbines used the paddle like wooden blades and thin sheets of wood until 1870, when the first steel bladed wind turbine put into operation for water pumping. 1 In 1968, the airfoil type fiberglass and plastic blades were used by German and Danish scientists. 2 After 80s, the power production stepped up from 1 or 2 megawatts to 10 megawatts per single turbine which required larger blades to extract the requisite amount of energy. The advancement put enormous pressure on the manufacturing industry to come up with right materials for turbine blades. As a result of that, glass-fiber reinforced polymers composites, epoxy based composites and carbon fiber reinforced materials were developed to achieve the set goals. More detail about these materials and their manufacturing techniques will come in the following text.

4


2 . Wind Turbine Blades With an increase in the size of modern utility scale wind turbines, the size of blades has increased tremendously over the past 25 years thus created a plenty of challenges for the manufactures to create durable as well as low cost materials for blade manufacturing. There are some issues related with the larger blades such as Larger blades produce more stress on the mechanical and gear components. The manufacturing cost would increase because of the complex and expansive molding The issues of logistics and transportation will be more complex. Larger blades have high tip speed ratio (the ratio of rotational velocity of blade tip and actual wind speed) so they create more sound. As we go offshore, the blade size gets even bigger and it clearly seems, within next two years, the market for blades larger than 50 meters would increase greatly. In the early years of wind power development, wood and metals were used to build wind turbine blades but these materials pose some limitations from megawatt industry’s perspective. As discussed earlier, wind turbine blades have been manufactured by metals e.g. steel and aluminum, composite materials e.g. wood, fiber glass and carbon fibers. The inertial and gyroscopic loads cause fatigue in the blades so they must be stiff, strong and at the same time lighter to curtail the effect of these loads. The steel and aluminum may not be the right choice for large blade manufacturing because of their high density, high cost and low fatigue life compared to modern composites. 3 During the last few years, composite materials mainly fiberglass has been used for manufacturing of blades. Some of the resins which are used in composites materials are polyester, vinyl-esters and epoxy. The carbon fibers are also being used because of their high strength to weight ratio. 4

2.1.

Blade Geometry

The design of blades is incredibly important to figure out the whole methodology behind wind turbine blades’ materials. Blades experience a wide range of loads from almost all directions. These loads include flapping, tension, compression and twisting. These loads can be 5


generated either by the movement of blades or by variable winds. In the following Figure 1, different loads are shown which act on wind turbine blades in general.

Figure 1. The loads acting on wind turbine blades (http://www.supergen-wind.org.uk/docs/presentations)

Today, the blades are optimized on the basis of low energy cost. The maximum annual energy production is not the main target for the developers now. In fact the low cost of wind power is the main goal, and to achieve this goal, efficient and cost effective blade geometry plays a key role. In the Figure 2, the inside structure of a blade is shown. The design of blade is optimized by making it a shell like structure. The central spar is used to make it stronger. The upper and lower spar caps are used to give strength and stiffness during bending and extension. The spar webs provide shear stiffness during the operation of blades.

Figure 2. Cross-Section of the wind turbine blade (http://web.mit.edu/windenergy/windweek/Presentations/Nolet_Blades.pdf)

6


3 . Wind Turbine Blade Materials

The design life of modern wind turbine blades is generally taken as 20 years and they normally rotate 10 9 times during their life. 5The basic design aspect for the wind turbine rotor blades is the selection of materials. The materials must be strong, stiff and light to achieve costeffective production. The selection of correct material is a tough task and is based on different factors such as properties of materials, performance, reliability, safety, affects on environment, availability, recyclability and most important, economics. The wind turbine rotor blades must be selected on the basis of following properties. The engineering design of rotor blade is dependent on the properties of materials. These properties are chemical, mechanical and thermal. The material of wind turbine blade must allow the blade to perform its function properly during its design life without failure. The material must be reliable and must be able to perform its function safely. The material should be easily accessible and must be available in large quantities. The cost of manufacturing or processing must be low to make it suitable for profitable wind energy production. The material must be able to withstand environmental influences during operational life of blades. The design of wind turbine blades is a complex task and it requires the optimization of properties, performance and economy. In wind turbine rotor blade, stiffness of material is required to maintain the optimal shape of performance, low density is essential to lessen the effect of gravity forces, extensive fatigue life is necessary to trim down the material degradation. Following are the different materials used for wind turbine blade manufacturing.

3.1.

Wood

Wood remained a common construction material for wind turbine blades for many years. Wood is a composite material of cellulose and lignin. Wood could be potentially very important manufacturing material due to its low density and environmental friendliness. But its low 7


stiffness confines it from being a right choice for large rotor blades because large blades suffer from high elastic deflections. Moreover the availability, in terms of large quantities, is another issue so it is difficult to conduct large scale economical manufacturing with wood.

3.2.

Steel and Nickel Alloy

Steel was once thought to be a perfect and optimum choice for blade manufacturing. Steel is an alloy of iron and carbon. Nickel alloy steel has also been used for blade manufacturing due good thermal and chemical properties like low corrosion etc. but during the last 20 years it was discarded due to its high weight high cost and low fatigue level. 3.3.

Aluminum

Aluminum has a lower density and lower cost than steel. It is a silvery white metal with good thermal conductivity and ductility. But it cannot be used for commercial blades due to its low fatigue level and less stiffness. However it can be used for testing purposes.

3.4.

Fiber

Fiber is a class of materials of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of threads. These materials are stiff and strong. Apart from their stiffness and strength, these cannot be solely used in the manufacturing of wind turbine blades. However they are combined in composite materials. 6 The fibers are divided into different sub classes e.g. glass fiber, carbon fiber, aramid, polyethylene and cellulose. In the following text, we will focus more on glass fiber and carbon fiber. 3.4.1. Glass Fiber

The constituents of glass fiber are the oxides of silicon and aluminum and some other oxides as well. The glass fiber is an amorphous solid and having properties like stiffness and thermal expansion. The glass fibers are made with different chemical compositions according to the specific requirements. The glass fibers are prepared by pulling the fibers from molten glass by the spinnerets and kept into huge bundles. A simplified picture of spinneret is shown in Figure 3 below7. The diameters of glass fiber is in the range of 10 to 20 m. 8 Their surfaces are coated

8


immediately with a polymer sizing which is used to guard them against cracking and enhance the bonding force with polymer matrix. 9

Figure 3. Spinnerets

The E-Glass Fiber is the most widely used fiber in composites. The E-Glass or Electrical Glass has excellent reinforcing capability. It has the composition SiO 2 54wt%, Al2O3 14wt%, CaO+MgO 22wt%, B2O3 10wt% and Na2O+K2O less then 2wt%.10 It has low cost. It possesses higher strength and high stiffness. It’s density is relatively low

Non-flammable, resistant to heat and has good chemical resistance. It has good electrical insulation It shows same properties over a wide range of variation in conditions. Some of the disadvantages are low fatigue resistance, low elastic modulus and higher density than carbon fibers. The glass fibers are used in different forms in Figure 3, some common forms are shown. 9


E-Glass Fiber

Carbon Fiber

Figure 4. Fibers 3.4.2. Carbon Fiber

The carbon fibers are composed of carbon which forms a crystallographic lattice with a hexagonal shape called graphite. The atoms are bounded by strong covalent bond. The carbon fibers provide higher strength than glass fibers and they are more useful in handling the fatigue. But they are more costly than glass fiber. Another issue is the electrical conductivity; their contact with metal can cause corrosion problems. Carbon fibers are produced by two methods. The first is Polyacrylonitrile (PAN) method and the second is Natural Tar method. 9 In the first method, PAN fibers are oxidized, heat treated up

10


to 1500 oC to 2500 oC and the original C-C backbone of PAN is coupled with graphite hexagon planes. The atomic structure of PAN is shown in the Figure 5 below. 11

Figure 5. C-C backbone of PAN In the second method, the natural tar mixtures containing graphite are processed through various steps and fiber is obtained from spinnerets. The first method is widely used for commercial purposes. However, research is in progress to find the cheaper raw material for carbon fiber manufacturing. In Table 1, properties of fibers are shown.

3.5.

Matrix Materials

The matrix materials are divided into two main classes’ i.e. thermosetting polymers and thermoplastic polymers. 12 These matrix materials are combined with fibers to make composite materials. The function of matrix materials is to bind the fibers in the composite materials and give structural stability to them. The stability and failure strain is moderate for thermosetting polymers, it is in the range of 5 to 8 % and for thermoplastics it’s usually 50 to 100 %9 that’s

how matrices give high strength to composite materials. Following is the description of thermosetting and thermoplastic materials. 3.5.1. Thermosetting Polymers

The thermosetting polymers are also divided into three subclasses i.e. unsaturated polyesters, epoxy resin and vinyl esters. 13 The thermosetting polymers have stiffness value in the range of 3 to 4 GPa and densities in the range of 1.1 to 1.3 g/cm 3. They provide internal strength in the composites through their irreversible curing action. 13The irreversible curing action means they could not adopt the same form as was before the curing. Unsaturated Polyesters The unsaturated polyesters are mainly used due to their low cost and

short cure time. They are based on orthophthalic acid or isophthalic acid. The orthophthalic acid 11


based polyester resins are less expansive but at the same time they are chemically less stable and more brittle than isophthalic acid based polyesters. Unsaturated means they have c-c double bonds in the polyester chain backbone and provide free locations for cross linkages while polyester means the recurring esters are linked together in a polyester chain back bone. The cross linking agent in c-c chain is mostly styrene. 10 It gives low viscosity which helps the processing of polyester resin. They can be cured at room temperature but it takes some times e.g. 5 to 6 hours however quick curing could be done at elevated temperature in short time.

Epoxy Resins In these resins, the epoxide ring structure serves as cross-linking site. Different

epoxy resins are being used in market e.g. di-functional epoxy resins like diglycidyl ether of bisphenol-A (DGEBPA) and tetra-functional epoxy resins like tetraglycidyl methylene dianiline (TGMDA). The strength at elevated temperatures could be shown in epoxidized phenolic novolacs resins and tetraglycidyl ether based resins however (DGEBPA) have high fracture toughness than others. The curing of epoxy resins are done at 150 oC for 3 hours under 1.4 MPa pressure. Different catalyst and curing agents such as Lewis acids or amines are also used.

14

Vinyl Esters There are different kinds of vinyl esters; either they are based on epoxy resins or

non-epoxy resins. But in the composite manufacturing, methacrylate ester is mostly used. 15 Their physical properties are quite similar to epoxy resins while they are could be cured in short time like unsaturated polyesters. In Table.1 different properties of thermosetting polymer are shown.

14

12


3.5.2 Thermoplastic Polymers

These polymers are of plastic that can be softened by heat, hardened by cooling, and then softened by heat over and over again. Thermoplastics are not cross-linked.The thermoplastic polymers are also available now for composite manufacturing. But most of them are under development. They have low values of density i.e. 0.9 g/cm 3 and stiffness i.e. 1 to 3 GPa. 16 Most of the research is being carried out on the recycling of thermoplastics. The difference between thermosetting polymers and thermoplastic polymer is that thermosetting polymers do not soften, and will only char and break down at high temperatures whereas thermoplastics remain permanently fusible so that they will soften and eventually melt when heat is applied. Thermosetting polymers are heavily cross-linked unlike thermoplastics. Thermoplastics can be recycled while thermosetting polymers cannot be recycled.

3 . 6 Composite Materials The fibers and matrix materials are combined to form a composite material. The fibers act as reinforcing agents and matrix materials act as binder. In some advanced composites, (polymer matrix composites) high-strength and high-modulus fibers are enclosed in polymer resin matrix.17 The most common composite materials are glass fiber composites. These have been used for many years in manufacturing applications. The glass fiber (70 to 75 % by weight) is bounded with the epoxy or unsaturated polyester resins. The glass fiber composites have moderate properties and these are mainly used because of their simple processing technology. The carbon fiber composites are better than glass fiber composite in terms of weight and stiffness. The use of carbon fiber composites has increased in large wind turbine rotor blades.

18

Due to the high cost

of carbon fiber composites, glass fibers and carbon fibers are combined to make a hybrid composite. These are combined on layer basis and are widely used to manufacture wind turbine blades. The properties of composite materials are dependent on the amount (volume fraction), orientation of fiber and bond between fiber and matrix materials. The physical properties of these two materials also affect the properties of the resultant composite material. Stiffness of composite material is an important property which can be calculated as follows.

Ec =

19

Vf *Ef + Vm+Em 13


Where,

Ec = Stiffness (elastic modulus) of composite material = orientation factor for fiber; For aligned parallel fibers loaded along the fiber direction=1 For a randomly oriented fiber assembly in two dimensions= 0.334

Vf , Vm = Volume fraction of fiber and matrix material respectively; for perfect composite with no porosity the sum will be equal 1.

Ef , Em = Stiffness of fiber and matrix material respectively

The composite materials are generally divided into two classes i.e. laminates and sandwiches. Laminates In laminates, piles or layers of composite materials are bonded together. This is

achieved by compiling the individual layers consist of high-modulus, high-strength fibers and matrix material. Typical fibers used include graphite, glass, boron, and silicon carbide, and some matrix materials are epoxies, polyimides, aluminum, titanium, and alumina. In laminates number of sheets, each having the fibers oriented in different directions is stacked and welded together to obtain high strength and stiffness within a plane. The arrangement is shown in the Figure below. 14


Sandwiches are the special forms of a laminated composite comprising a combination of

different materials that are bonded to each other so as to utilize the properties of each separate component to the structural advantage of the whole assembly. Typically a sandwich composite consists of three main parts; two thin, stiff and strong faces separated by a thick, light and weaker core. The faces are adhesively bonded to the core to obtain a load transfer between the components. Polyvinyl chloride, polyurethane, polystyrene foams, balsa wood, synthetic foams and honeycombs are used as core materials. An adhesive is used to bind core material with the layers of composite material

Sandwich Composite

Fi ure 6. Stiffn Stiffness ess versus versus den densit sit

Laminate Composite

ra h of diffe differe rent nt mater material ialss

15


4

Manufacturing Technologies After the energy crisis in 1970, the wind turbine manufacturing techniques took a revolution.

Especially the blades increased in size and quantity, the manufacturing processes also shifted from inefficient, wet and open towards more sophisticated ones. Following is the details of the processes and techniques.

4.1

Wet Hand Lay Up

It is the oldest manufacturing technique for making wind turbine blades. In this process, fibers are impregnated by resins in an open mold and allowed to cure under standard atmospheric conditions. Usually fiber glass and polyester resins are used in this technology. The fibers could have any specific orientation in the composite.

20

The upper and lower shells are adhesively bound together to form an airfoil structure. For large blades, webs are inserted into the foils to withstand bending and shear loads. In order to improve the stiffness of blades, the fiber orientation is changed and unidirectional woven fiber in the longitudinal direction is used. In some cases fiber roving are laid up parallel with Chopped strand mats. The fiber roving is also used to make the root end of rotor blade. They are wound around the steel bushes or tubes and continued back into the blade. These steel bushes form the holes which become flange of the blade. This flange is used to fix the blade with rotor hub. Advantages Advantages

The process is quite simple. Cost of tooling is incredibly low Wide range of fibers and resins can be combined Disadvantages Disadvantages

Since it is an open process, so the Health, Safety and Environment (HSE) pose lot of limitations The quality of final product and also the intermediate steps are dependent on human skills. The process only requires low viscosity resins because they are easily operated. The labor cost is much higher for this process.

16


4.2

Filament Winding

In filament winding process, the fiber material and resin are wound together around a shape, called mandrel, to make composite material. The filament winding process can employ many different fibers and resins to get the required characteristics for the finished product. The end result is an extremely efficient process to create low cost, lightweight, and strong composite material. This technique was developed in 1970s after hand lay ups techniques. Kaman Aerospace Corporation and Structural Composites Industries in United States developed 45 m long blade using this technology. 21 Advantages Advantages

Low weight and stiff composites can be manufactured by this technology The filament winding technique can be done by high speed automation The labor cost is very low so overall cost of this process is low compared to hand lay ups. Disadvantages Disadvantages

The finished product from filament winding technique has rough external surface which is not acceptable for upper side of an airfoil. The viscosity and pot life of resin must be carefully chosen Some shapes are not easily made by this technology

Wet Hand up Technique 26

Filament Winding Technique 26

Figure. 7 17


4.3

Prepreg Technique

In prepreg (pre-impregnated) technology, the fiber material is pre-impregnated with resin at room temperature to form an intermediate product. This intermediate product (prepregs) is then stacked and subjected to high temperature and pressure where resin melts and consolidates the fiber fabrics. The product is now subjected to be cured. This technique is widely used in aerospace industry. For large wind turbine blades the prepregs are cured at 80 decreases the process and product cost.

22

o

C which

Vestas Wind Systems, one of the wind turbine

manufacturers, uses the prepreg technology for their blade production. Vestas has used glass/epoxy prepreg technology for many years, and they have now introduced carbon fibers in their 45-m-long blades. 23

Advantages Advantages

It is easier to control and obtain constant material properties and higher fiber content gives stiffness and lower weight to final product. The process is clean so no limitations from Health, Safety and Environment (HSE) Automation could be installed to enhance the efficiency of overall process Disadvantages Disadvantages

Vacuum bagging is required for this process which increase the cost of process Expansive oven system is required It is difficult to bag complex shaped parts of composite materials

4.4

Resin Infusion Technology

In this manufacturing technology, the dry fibers are sited in a mold, which seals and encapsulate the dry fibers from all sides. The liquid resin is then injected into these molds, and the components are kept to cure for some time. The technology was developed in 1950s but after 1990s it has been widely adopted by the industry. The fibers, resins and all the accessories have been developed now. One of the important issues related with Resin Infusion Technology is the proper wetness of fibers during the process. 24 This problem has vastly been addressed by the researchers but still more work is need in this field. However following are some parameters which can solve this issue.

18


The fiber material should be designed and oriented in a special way to control the flow regimes of resin. The viscosity of the resin should be lower to enhance the wetability of fiber. The control of volatile release from resins under vacuum because it creates voids in flow. Proper accessories must be used for resin flow i.e. resin distribution mesh etc. Continues mixing of resin without introducing air because the air bubbles affect the proper layer mixing of resin The designs of mold should allow proper flow of resins through fiber materials. The instruments, computer modeling is required for flow measurements and flow prediction. LM Glass fiber in Denmark, the leading blade manufacturing company, uses resin infusion technology and recently it has manufactured 61.5 m long blade using this technology.

25

There are

three methods to perform resin infusion technology.

4.4.1 Resin Transfer Molding (RTM) In RMT technology, dry and pressed stack of fiber material is laid into a mould, sometimes the mold shape is given to the stack for better fitting. After that, upper mould tool is kept on the stack and resin is injected from the inlet cavity. Once all the fiber material is wet, the resin inlets are closed and the laminate is allowed to cure under room temperature or elevated temperatures. Vacuum can also be applied to the mould for better flow of resin. This technique is called Vacuum Assisted Resin Transfer Molding (VARTM). Any combination of fiber and matrix material can be used for RTM however bismaleimides resins work well at high temperatures while stitched fibers provide good flow patterns for resins.

26

Advantages Advantages

Closed processing technology provides good health, safety and environment (HSE) control High fiber volume laminates could be attained with low void contents. The final component is molded from both sides so it gives more strength. The labor cost is low for this process

19


Disadvantages Disadvantages

Sometimes un-wetted fractions of fiber fabric ruined the whole mass and it is very expansive to discard the scrap. It works very fine with smaller components. 4.4.2

Seeman Composite Resin Infusion Molding Process (SCRIMP)

In this process, dry fiber material is stacked in an open mold and is covered with a nonstructural knitted type fabric and a solid layer. The whole structure is kept in vacuum to remove the voids within the materials. After vacuum treatment, the resin is transferred trough nonstructural fiber in to the fiber material wets the whole laminate. 27 Epoxy, polyester and vinyl esters are generally used resins with any fiber materials. The difference between (SCRIMP) and (VARTM) is that initial step of (SCRIMP) is carried out in an open mold while in (VARTM) every step is done in covered molds. Another difference is that a non-structural fiber is used in the first step of SCRIMP while this is not the case with (VARTM) Advantages Advantages

The cored structures can be produced in one operation. Tooling cost is lower than RTM Large components could be manufactured. The standard tools for wet layout could be modified for this process Disadvantages Disadvantages

It is a complex process Resin should be low in viscosity Scrap problem is same as with RTM

4.4.3 Resin Film Infusion (RFI) In this process, the dry fiber fabric is stacked with semi-solid layers of resins. The assembly of fiber and resin is subjected to vacuum to remove any air entrapped. Then the whole structure is heated and cured to make a stiff composite. 28 Generally epoxy resins are used with any kind of fiber material while polyvinylchloride is usually taken as core material. Advantages Advantages

The void contents are generally very low in the composites prepared by this technology. Lower cost than Prepreg technology.

20


The Health, Safety and Environment (HSE) are well controlled Disadvantages Disadvantages

This process is not well proven outside the aerospace industry Tooling cost is generally higher because the treatment includes variable temperature ranges Costly oven and vacuum system is needed Core materials suffer from high temperature and pressure

Resin Transfer Molding 26

SCRIMP28

Resin Film Infusion 27

Figure. 8

5

Conclusion As fuel prices rise and the climate warms everyone is looking for alternative sources of

energy to power our lives and wind is an obvious source. Wind turbines have been used to capture energy from the wind for many years. The success of wind turbine depends heavily on the correct blade design and its life. The blade life and its sustainable operation both are dependent on the material of construction. The material selection is very important task because the planner has to make a very delicate optimization of strength and economics in order to keep the wind power project potentially and economically viable.

21


References 1

http://telosnet.com/wind/early.html (Retrieved on October 13, 2011)

2

http://telosnet.com/wind/20th.html (Retrieved on October 13, 2011)

3

Mayer, R.M., ―Design of Composite Structures against Fatigue‖ Mechanical En gineering Publications Limited, ISBN 0 85298-957-1, first publication 1996

4

James L. Tangler, ―The Evolution of o f Rotor and Blade Design‖ Presented at the American Wind Energy Association Wind Power 2000 Palm Springs, California, April 30-May 4, 2000

5

K.S. Babu, N.V.S. Raju, M.S. Reddy, Dr. D. N. Rao, ―The material selection for typical wind turbine blades using a MADM approach& analysis of blades ‖ June 2006 Page no. 3

6

Bunsell AR. ―Fibre Reinforcements for Composite Materials ‖ Amsterdam: Elsevier 1988. 537 pp 7

http://www.madehow.com/Volume-1/Rayon.html

8

Watt W, Perov PV. 1985. Strong fibres. In Handbook of Composites, ed. A Kelly, YN Rabotnov. Amsterdam: North Holland/Elsevier. 755 pp

9

Chou TW, ―Fibre reinforcements and general theory of composites‖ ed. 2000

10

http://www.azom.com/article.a http://www. azom.com/article.aspx?ArticleID=76 spx?ArticleID=764 4

11

http://pslc.ws/macrog/pan.htm

12

Talreja R, M°anson J-AE. 2000. Polymer matrix composites. See Ref. 95, 2:1129

13

Lee H., and K. Neville. 1967. Handbook of Epoxy Resins. McGraw-Hill, New York.

14

―Assessment of Research Needs for Wind Turbine Rotor Materials Technology‖ Committee on Assessment of Research Needs for Wind Turbine Rotor Materials Technology, National Research Council, ISBN: 0-309-58318-7 pp 41

15

Launikitis, M. B. ―Chemically Resistant FRP Resins‖ Technical Bulletin of Shell Chemical Company, 1978 16

Witzler, S. 1988. High-Temperature Thermoplastics: A Progress Report. Advanced Composites, March/April, p. 56

17

Rufe, P.D., ―Fundamentals of Manufacturing‖, Society of Manufacturing Engineers, 2nd Ed. 2002 22


18

Lilholt H, Madsen B, Toftegaard H, Cendre E,Megnis M, et al., eds. 2002. Sustainable natural Risoe Int. Symp. Mater. Sci. and polymeric composites — science and technology. Proc. 22nd Risoe Int. Risoe Natl. Lab., Roskilde, Denmark. 371 pp 19

Jones RM. ―Mechanics of Composite Materials ‖ New York: McGraw-Hill, 1975. 355 pp

20

http://www.fibre-reinforced-plastic.com/2009/01/composite-fabrication-hand-lay-up-wet.html

21

1976. Design study of wind turbines 50 kW to 3000 kW for electric utility application. Kaman Rep. No. R- 1382, ERDA/NASA — 19404 19404 — 76/2. 76/2. pp. 4 – 5, 5, 4 – 51, 51, 4 – 79. 79. Kaman Aerospace Corp., Bloomfield, CT 22

http://engineeronadisk.com/notes_manufact/composita3.html

23

http://www.vestas.com/produkter/pdf/updates 020804/V90 3 UK.pdf

24

Hancox NL, Mayer RM. 1994. Design Data for Reinforced Plastics, A Guide forEngineers and Designers. London: Chapman & Hall. 326 pp.

25

http://www.lm.dk

26

Johnson, Carl F Engineered materials handbook. Vol. 1 - Composites (A95-28858 07-24), Metals Park, OH, ASM International, 1993, p. 564-568

27

X. Sun, S. Lee, J. Lee, ―Mold filling analysis in vacuum-assisted resin transfer molding. Part I: SCRIMP based on a high- permeable medium‖ April 15 2004

28

B. Qi, J. Raju, T. Kruckenberg, R. Stanning A resin film infusion process for manufacture of advanced composite structures Composite Structures, Volume 47, Issues 1-4, December 1999, Pages 471-476 26

http://www.frprawmaterial.com/frp-process.html

27

http://autospeed.com/cms/title_Complete-Guide-to-Composites-Part-6/A_108698/article.html

28

http://powercatamaran.typepad.com/homeport/pdq

23

Materials and Manufacturing Techniques for Wind Turbine Blades

Recommend Documents