Koh 2015

Prepared for: Massachusetts Wind Working Group

September 30th, 2015

Rachel Koh

Ph.D. Candidate, University of Massachusetts Amherst

Advisors: Peggi Clouston, Bob Hyers, Matt Lackner

Bio-based Materials for Large Wind Turbine Blades

2 Koh 2015

Motivation for Large Wind Energy

4.13% of US electricity generated by wind in 2013

30% of all new generating capacity from 2009-2014

𝑃 =1

2𝜌𝐴𝑉3

Wind turbine rotor size trends from Fichaux (2011), DTU-Riso

3 Koh 2015

Basic Considerations for Blade Materials

Stiffness

• retain airfoil shape

• tower clearance

Strength

• tension, compression, bending

• fatigue

Density

• influences strength requirement

Hull, MA municipal wind turbine photo: R. Koh

4 Koh 2015

Concerns with fiberglass and carbon fiber

Fiberglass

• mass scaling

• recyclability / end-of-life disposal options

• global production increase from 5.9 million metric tons in 1999 to 8.7 million in 2011

• ~10% global fiberglass market share for wind energy and increasing

Carbon fiber

• expensive

• brittle

• energy intensive production

Blade Mass Scaling Relationships from NREL Cost and Scaling Model

5 Koh 2015

Advantages of Bio-Based Materials

Competitive specific stiffness and strength

Competitive fatigue properties

Ashby chart for Plant Fiber Reinforced Polymers from Shah (2013) at Oxford U.

6 Koh 2015

Advantages of Bio-Based Materials (cont’d)

Renewable (unlimited resource)

Biodegradable when triggered

Low emissions manufacturing

• EU- Directive on Landfill of Waste and End-of-life Vehicle Directive are seen as barriers for development and continued use of glass and carbon in some markets

Low cost raw materials

“Bio-inspired” and “Biomimicry” engineering

7 Koh 2015

Challenges with Bio-Based Materials

Variable mechanical properties

Limited experimental data for complex loading conditions such as off-axis and multiaxial loading

High sensitivity to moisture

Not fully developed manufacturing processes

8 Koh 2015

Current Projects

Shear Properties and Failure Mechanics of Angle-Ply Wood Laminate Beams

Yield Criteria Assessment for Multiaxial Wood Laminate and Flax Fiber Reinforced Composites

FEA of Wind Turbine Blades with Material Property Variability using Probabilistic Design

Koh 2015

Shear Properties and Failure Mechanics of Angle-Ply Wood

Laminate Beams

10 Koh 2015

Multidirectional Materials in Wind Turbine Blades

Adapted from Gurit Corporation (2014).

11 Koh 2015

Torsion Test for Shear Strength and Stiffness

Adapted with permission from Yang (2012).

13 Koh 2015

Torsion Test Configuration (ASTM D198)

14 Koh 2015

Preliminary Torsion Test Results

0 5 10 15 20 25 30 35 40 45 500

100

200

300

400

500

600

Twist (degrees)

Torq

ue (

N-m

)

Torsion Test Results

angle-ply

unidirectional

15 Koh 2015

Possible failure modes under torsional loading

(𝜏𝑧𝑥) (𝜏𝑦𝑥)

rolling shear failure

Koh 2015

Yield Criteria Assessment for Multiaxial Wood Laminate and

Flax Fiber Reinforced Composites

18 Koh 2015

Multidirectional Materials in Wind Turbine Blades

Adapted with permission from Gurit Corporation (2014).

19 Koh 2015

Fabrication Process (90% of research)

20 Koh 2015

Mechanical Testing

21 Koh 2015

Preliminary Results

0 0.2 0.4 0.6 0.8 1 1.2 1.40

10

20

30

40

50

60

crosshead displacement (mm)

str

ess (

MP

a)

0 degrees

30 degrees

45 degrees

60 degrees

90 degrees

22 Koh 2015

Preliminary Results (cont’d)

-20 -10 0 10 20 30 40-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5Biaxial Failure Envelopes for Several Composite Failure Criteria

1 (MPa)

2 (

MP

a)

Tension Tests

Compression Tests

Tsai-Wu

Tsai-Hill

Hoffman

Chamis

23 Koh 2015

Future Tasks

multiaxial flax composite tests

develop finite element material model to reflect multiaxial test data

finite element design of hybrid bio-based 5MW blades

24 Koh 2015

Acknowledgements

Committee: Professor Bob Hyers (MIE), Assoc. Professor Peggi Clouston (ECO), Assoc. Professor Matt Lackner (MIE), Adjunct Faculty John Fabel (ECO)

Undergraduate Students: Alex Finn (MIE ‘14), Jesse Turek (BCT ‘14), Charlie Tormanen (BCT ‘15), Malia Charter (Smith College ’16), Melody Cao (Smith College ‘16), Yashira Valentín Feliciano (University of Puerto Rico)

Funding source: NSF Offshore Wind Energy IGERT Grant Number 1068864