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Thermoplastic Composite

Development for Wind Turbine Blades

NREL: Derek Berry and David Snowberg, TPI Composites: Steven Nolet

CSM: John R. Dorgan, Yasuhito Suzuki, Dylan Cousins, Aaron Frary, David RuehleJohnsMaville: Jawed Asrar, Klaus Gleich, Mingfu Zhang, Michael Block

Arkema Chemical: Dana Swan, Robert Barsotti, Mark AubartColorado OEDIT: Katie Woslager

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Thermoplastic Composite Development for Wind Turbine Blades

• Wind, Project 4.2

• TRL/MRL Impact: from 3 to 4

• Challenge: Fiber reinforced polymer composites are the material of choice for large scale wind turbine components, but challenges in manufacturing costs, performance, and recyclability are limiting.

• Approach: Development of thermoplastic materials to lower production costs and improve recyclability of wind turbine blades and applicability to components demonstrated at large scale.

• Impact: Cost reductions in composite materials for wind turbine blades will enable lower cost of electricity; property improvements enable larger scale and increased efficiency.

• Partners: NREL, TPI, Johns Manville, Colorado School of Mines. Arkema joined in BP2 (new partners expected in BP3).• Cross-cutting partnering includes

NDE team from Vanderbilt, and ORNL/University of Tennessee.

• Simulation tool development in conjunction with Purdue group and Convergent

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Thermoplastic Composites – Accomplishments

• Added Arkema as major new corporate partner

– Work plan expanded to include innovative EliumTM system

• Commissioned two new facilities

– VARTM lab at Colorado School of Mines (CSM) (Fabricated proof of concept panels at CSM, JohnsManville, and Arkema).

– Blade component manufacture at NREL Wind Technology Center (thick root section mold arriving soon – demonstration at scale)

• Property database creation

– Collected rheological data for liquid precursor and curing resin

– Established testing protocols and plan for comparison to thermosets

• Cross-cutting: Modeling and Simulation

– Developed chemical kinetics / heat transfer model and initiated transfer to Convergent for incorporation into Raven process simulator.

• Cross-cutting: Non Destructive Evaluation (NDE)

– Established thermal imaging / emission FTIR

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• Complementary facilities at Johns Manville in

Littleton, Colorado (just 15 miles away).

VARTM Lab at CSM

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Demonstration scale at NREL

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Wind Turbines - More and Bigger

A 60m blade weighs 10 tons and is 30 wt% polymer resin.

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Wind Turbines – Program Goals

• Increase jobs for American workers.

• Increase domestic production capacity.

• Reduce life cycle energy use and associated greenhouse gas emissions. Double the energy productivity of fiber reinforced polymer composite manufacturing.

• Demonstrate at scale reduced embodied energy and associated greenhouse gas emissions.

• Demonstrate at scale greater than 80% recyclability.

Thermoplastic based composites enable reaching these goals!

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Why Thermoplastics?

Plastics are characterized according to their response to temperature:

Thermoplastics - soften and flow upon heating:

Tg - Glass Transition Temperature

(beginning of chain motion over several segments)

Tm - Melting Temperature (chains can self-diffuse)

(for semi-crystalline polymers)

Some thermoplastics are amorphous glasses without melting temperatures.

Thermosets - rigid until thermal decomposition

Epoxies, unsaturated polyesters, and other

network forming materials that are used today

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Why Thermoplastics?

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Thermoplastic infusion

VARTM – Vacuum Assisted Resin

Transfer Molding.

Low viscosity resins infused

and then cured in mold / autoclave.

Not injecting high viscosity preformed polymers!

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Thermoplastic infusion

“Acrlylate based”

- Dana Swan

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Johns Manville Innovation

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Johns Manville Innovation

TRL is suitable for NNMI

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Experiments at CSM

• Samples of methylmethacrylate (MMA) monomer immersed in constant T bath.

• J-Type thermocouples with a data logger.

Wall temperature

25 C

2 hour cure time

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Experiments at CSM

0 20 40 60 80 100

20

40

60

80

100

Tem

pera

ture

(oC

)

Time (min)

Initiator concentration

0.5 wt%

1 wt%

3 wt%

5 wt%

Elium has a lower exotherm.

Initiator is analogous to hardener / curative in epoxy systems.

Less initiator means slower reaction and lower peak temperatures due to increased time for heat transfer

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Cross-Cutting : Model Development

Chemical kinetics coupled to heat transfer and including “gel effect” due to diffusional limitations

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Cross-Cutting: Model Development

0 10 20 30 40 50

20

30

40

50

60

70

80

90

100

Tem

pera

ture

(oC

)

Time (min)

0.5 wt%

1.0 wt%

2.0 wt%

3.0 wt%

Initiator concentration

0 10 20 30 40 50 60 70 8020

40

60

80

100

120

Tem

pera

ture

(oC

)

Time (min)

0.5 wt%

2.0 wt%

5.0 wt%

Qualitative description based on literature values

Determining parameter set for quantitative description

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Process Modeling with RAVEN

RAVEN is a desktop composites processing analysis program that allows users to design, optimize, and troubleshoot processing of composites.

RAVEN is used for:

• Cure cycle optimization

• Thermal profiling

• Troubleshooting

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2000 4000 6000 8000 100001000

10000

100000

1000000G

' [P

a]

Reaction time [s]

Elium Polymerization at 40°C

Elium reaction rheology experiments take place in two steps:

1) Measure the viscosity as a function of time at a constant shear rate of 100 1/s with the gap fixed at 1 mm:

0 500 1000 1500 2000 2500

0.1

1

10

100

[P

a s

]

Reaction time [s]

Elium Polymerization 40°C

.

2) When the torque on the geometry reaches a cutoff value, switch to an oscillatory measurement at 3.33 rad/s and allow the gap to change to produce an applied normal force of 0.5 N:

2000 4000 6000 8000 10000

3

4

5

6

7

8

9

10

11

12

13

14

Volu

metr

ic S

hrinkag

e (

%)

Reaction time [s]

Elium Polymerization at 40°C

𝜀𝑣 = 1 +1

3

ℎ − ℎ0ℎ0

3

− 1

h = gap heightho = initial gap height

Rheology and shrinkage data for simulation

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• Elium with 3 wt% initiator package

• 40 minutes time lapse

• Frame speed is 1 min or 30 s during rapid temperature change.

Heat imaging during infusion

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Phase Change Materials (PCMs)

• Recall:

– “Sensible” heat is energy to raise the T of a given phase (water in this graph).

– “Latent” heat is the energy needed to change phases; to melt a crystal for example. This is more properly the “heat of fusion”.

– Latent heats are much larger than sensible heats.

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Phase Change Materials (PCMs)

• PCMs have become widely used:• Domino Pizza “Heat Wave” bag

• Every laptop has a “heat pipe” which uses liquid to gas vaporization

• Outlast Technology (now part of CoorsTek) adopted NASA space suit technology to outdoor clothing.

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Effect of commercial PCMs on EliumTM

0 500 1000 1500 2000 2500 3000 3500 4000

20

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100

Te

mp

era

ture

(oC

)

Time (s)

Elium

Elium +10 wt% PCM

Elium +20 wt% PCM

Crystallization of PCM

Same initiator composition

0 10 20 30 4020

40

60

80

100

Tem

pera

ture

(oC

)

Time (min)

5.0 wt%

5.0 wt% (with PCM)

3.0 wt%

PCMs enableshorter cycle times!

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Slow motion during the curing reaction

NDE – cold spots reveal problems and in situ

emission FTIR can provide cure information

With PCMWithout PCM

Heat imaging during infusion

Tpeak = 104 C Tpeak = 84 C

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Thermoplastic Composites Team

• Met all budget period 1 milestones and on-track to meet all period 2 milestones

• Commissioned two new facilities

– VARTM lab at Colorado School of Mines (CSM)

– Blade component manufacture at NREL

• Property database creation

– Collected rheological data for liquid precursor and curing resin

– Established testing protocols and plan for comparison to thermosets

• Developed chemical kinetics / heat transfer model

– Initiated tech transfer to Convergent for Raven process simulator.

• Developed NDE plan (Vanderbuilt / ORNL group)

• Demonstrated that PCMs can shorten cycle times

• Filed 1 patent, submitted 1 paper + 1 CAMX abstract, 2 more patents in preparation.

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Acknowledgements

• Colorado Office of Economic Development Industry and Trade (CO OEDIT) with special thanks to Katie Woslager.

• The IACMI team in Tennessee.

• You for your attention!

jdorgan@mines.edu