Blade with Shear Web bonded to Spar Cap

Sandwich Shell

TE Shear Web

LE Shear Web

Trailing Edge

Sandwich Shell

Sandwich Shell

Sandwich Shell

Lower (HP) Spar Cap

Upper (LP) Spar Cap

2

Leading Edge

Source:http://www.compositesworld.com/articles/wind-blade-manufacturing-targeting-cost-efficiency-through-materials-based-strategies.aspx 4/5/2009

Blade Objectives

Figure from GE

Blade Objectives

• Maximize annual energy yield• (limit maximum power)• Resist extreme and fatigue loads• Restrict tip deflections• Avoid resonances• Minimize weight and cost

Burton, Sharpe, Jenkins, Bossanyi: “Wind Energy Handbook”

UTS UCS UCS/sg Fatique % of UCS

Stiffness/sg

E/UCS^2

Glass/X 880 720 390 19 20 .07

Glass/polyester

700 580 310 21 18 .1

Carbon/epoxy

1830 1100 700 32 90 .12

Birch/epoxy

117 81 121 20 22 2.3

Steel: fatigue and mfgblty

Blade Materials

• compressive strength-to-weight ratio,• fatigue strength as a percentage of

compressive strength,• stiffness-to-weight ratio,• a panel stability parameter, E/(UCS)2.

April 18, 2023 8Courtesy: Nolet, TPI

Power, Length and Weight

Burton, Sharpe, Jenkins, Bossanyi: “Wind Energy Handbook”

Polymer Matrix Composites & Processes

General Composite Information

• Composites: 2 or more physically distinct phases

• Properties are better than the constituents

• High strength to weight ratio• Also. . Corrosion, fatigue, toughness, surface

finish

Why nots . . .

• (many have) anisotropic properties• Polymer based may be subject to chemical

attack• Cost?• Manufacturing process often slow and costly

(Groover p 177)

2 or more phases

• Matrix (primary phase)– Polymer, metal, or ceramic

• Reinforcing agent (imbedded phase)– Polymer, metal, ceramic, or element– Fibers, particles, . . .

Possible combinations for 2 phases

Fiber reinforcement

• Diameters of 0.0001 to 0.005 inches• As D ↓, orientation ↑, probability of defect↓– tensile strength↑ ↑

• Orientation:– Unidirectional, planar, 3 dimensional

Fiber Reinforced Polymer Composites

• Short fibers:– Open mold: spray up– Closed mold processes

• Long fibers:– Open mold: hand, automated tape machines– Closed mold– Filament winding– Pultrusion

Materials

• Polymer matrix– Thermosets: most common– Thermoplastics

• Reinforcing– Glass– Carbon– Kevlar (polymer)

Composing Composites . . .

• Molding compounds– Mix short fibers and matrix

• Prepegs– Fibers impregnated with partially cured TS matrix– Allows fibers to ‘stay put’– Continuous fibers

• Or done in the mold

Open Mold Process

• Spray up– Requires mold– Discontinuous fibers // random orientation– Mixture of fiber and matrix deposited in mold

• Automated tape laying machine– Requires mold– Requires use of prepeg– CNC control

Image sources: http://www.bauteck.com/manufacture/Manufacture2.htm 4/5/9 http://www.mmsonline.com/articles/getting-to-know-black-aluminum.aspx 4/5/9

Filament Winding• Wound around mandrel or part of final

component• Continuous fibers– Matrix added before or after winding

• Automation controls wrap pattern

Source:http://sacomposite.com/filament_winding_carbon_fiber.html 4/5/9

Pultrusion

• Continuous fibers• Dipped into matrix • 2 options:– Pulled through die and cured– Laid up into an open mold (and later cured)

Source: http://www.ale.nl/ale/data/images/Pultrusion.jpeg 4/5/9

http://www.tangram.co.uk/TI-Polymer-Pultrusion.html

Open Mold Processes

• Hand lay up– Oldest, labor intensive– Mold required– Fibers placed in mold:• Dry fibers placed and then matrix added

– Pour or brush or spray >> rolled to achieve mixture– Vacuum used to ‘pull’ matrix into fiber

• Prepeg placed in mold

Burton, Sharpe, Jenkins, Bossanyi: “Wind Energy Handbook”

Burton, Sharpe, Jenkins, Bossanyi: “Wind Energy Handbook”

Source: www.tpicomposites.com 3/2008

Source: www.tpicomposites.com 3/2008

Source: www.tpicomposites.com 3/2008

Reusable Silicon Bag Technology for SCRIMP®

April 18, 2023 28

o Silicone bags are rapidly fitted to the infusion toolo Feed lines, vacuum lines and embossed distribution channels are integrated into the bag improving the repeatability of the process (TPI Patented Technology)

Courtesy: Nolet, TPI

Fibers• Woven Fabrics– Higher cost, less applicable as

structural components for blades

• Non-woven Multiaxials– Most widely used in VARTM processes– Low-cost, non-crimp form results in

superior performance– “Uni-directional”, Biaxial, Double Bias,

Triaxial and Quadraxial material forms available.

April 18, 2023 29

Courtesy of Saertex USA

Courtesy: Nolet, TPI

Resin Matrices

• Epoxies remain a primary resin of use in European based blade designs

• Vinyl-esters are attracting much interest by blade designers

• Polyester resins are still prominent in the industry.

• Thermoplastics and other matrices

April 18, 2023 30Courtesy: Nolet, TPI

http://www.compositesworld.com/articles/carbon-fiber-in-the-wind.aspx

Blade Components

Infused Together• Skin

– Composite– Core

• Spar cap– Composite

• Shear web– Composite– Core

• Root Section– composite

Other Materials• Bond paste• Hardware• Balance box• Paint• Lightening protection

system• Platform

Quality Issues

• Waves– Aspect ratio (L/a)

• Bond failure• Dry infusion• Lack of continuous fibers• Geometrical errors• Fabric assembly errors

Figures from: “Yerramalli, Miebach, Chandraseker, Quek: “Fiber Waviness Induced Strength Knockdowns in Composite Materials Used in Wind Turbine Blades”. 2010

Process Steps• Cut fabric• Preforms

– Layup– Infuse– Inspect– Trim

• Shell– Layup– Install preforms– Infuse

• Assembly– Shear web– 2 shells

• Finishing– Finish edges– Wet layup

• Final cure• Drill and cut end square• Finishing and painting• Hardware• Balance box• Final inspect

Burton, Sharpe, Jenkins, Bossanyi: “Wind Energy Handbook”

Burton, Sharpe, Jenkins, Bossanyi: “Wind Energy Handbook”

Mark Higgins 9/15/2011 Presentation at ISU

Mark Higgins 9/15/2011 Presentation at ISU

Mark Higgins 9/15/2011 Presentation at ISU

Mark Higgins 9/15/2011 Presentation at ISU

Mark Higgins 9/15/2011 Presentation at ISU

Mark Higgins 9/15/2011 Presentation at ISU

Assembly Variation

43

• Maintain +-mm across 50m assembly

• Joints are critical

http://mag-ias.com/index.php?id=308&L=2

Rapid Material Placement Systems (RMPS)Automated blade molding

Automated root end machining for wind bladesMachine adapts automatically to blade position Machining processes: Sawing, milling, boring and trimming

Future Automation Systems?

Options for Large(r) Blades

• Manufacturing– Make at point of use– Make in region of use– Import

• Design– Flatback design– Design in 2 pieces– Materials to reduce

weight

Remote Blade Manufacturing Demonstration – Sandia 2003