Vacuum infused thermoplastic composites for wind turbine ... · Thermoplastic wind turbine blades 9...

28-10-2009

Challenge the future

DelftUniversity ofTechnology

Vacuum infused thermoplastic composites for wind turbine blades

Julie Teuwen, Design and Production of Composites Structures

2Thermoplastic wind turbine blades

Introduction

WIND ENERGY:

• Promising renewable energy source

• Fast growing market share in energy supply

WIND TURBINE BLADES:

• Length > 50 m• Life expectancy ≈ 20 years


Large Wind Turbine Blades

• Dedicated Offshore Wind Power Systems:• Stronger and more constant wind

• Increasingly large blades to increase power output per turbine and

reduce cost per kWh

• No noise-pollution and aesthetical issues

• Larger blades require:• Materials with higher specific properties (E/ρ, σ/ρ):

• Carbon fibre based composites

• More efficient structural design

mblade ∼∼∼∼ (Rblade ) 32.35


Current blade manufacturing technology

• Material:• Glass fibres (NCF’s)

• Thermoset resin

• Process:• Vacuum infusion

• Prepregging

• Design:• 2 skins and 1 spar

• Structural bonding

Design

Material

Process


Alternative structural design

• Re-introduction of ribs:• Higher structural efficiency (E/ρ)

• Reduces buckling of the spar

• Provides attachment points and load paths for smart actuators,

control surfaces and sensors


Why thermoplastics?

• Processing:• Forming

• Assembly by welding

• Properties:• Good impact properties

• High toughness, also at low temperatures

• Abrasion resistant

• Chemical resistant

• Life cycle:• Unlimited shelf-life of raw materials

• Short production cycle time

• Fully recyclable

Pre-cut laminate sheet material

Infra red heating panels

Rubber die

Metal die

Rubber press

Final thermoplastic composite part

Heating element

Clamp connection

Welded parts

Voltmeter

Ampmeter


What still stands in the way?

• Costs:• Technology costs:

• New technologies and expensive equipment

• Material costs:

• Need for intermediates

• Processing:• High processing temperatures (>200°C):

• High costs, thermal stresses

• Melt pressing technology:

• Limits part size and thickness

• Properties:• Fatigue performance:

• Weak fiber-to-matrix bond

Monomer

Polymer

PowderGranules

Film Solution

Laminate Prepreg

Finalproduct

Tradit

ional

Proce

ssing

of

Therm

oplas

t ic Com

posi

tes


Vacuum infusion of thermoplastic

composites

• Reactive processing:

• Processing:

• From the monomer directly to the polymer

• Large, thick, integrated parts

• Commonly used technology

• Below melting temperature of polymer

• Properties:

• Improved fibre-to-matrix bond


Vacuum infusion of thermoplastic

composites

• Selection of resin:• Low processing

temperature (150-180˚C)

• Low viscosity (10 mPa.s)

• Low price/performance

(2-3€/kg)

Anionic Polyamide-6:

• AP-Nylon®

• World wide availability

0,001

0,01

0,1

1

10

100

1000

10000

100000

0 50 100 150 200 250 300 350 400 450

Processing temperature [ºC]

Mel

t vi

scos

ity [

Pa·

s]

epoxyvinylester

polyester

PMMA

PA-6

PBT

PA-12

PEK

ETPUPC

PMMAPA-12

PA-6

PBTPPS

PES

PEI

PEEK

PEKK

Reactive processing of thermoset resins

Reactive processing of thermoplastic resins

Melt processing of thermoplastic polymers

0,001

0,01

0,1

1

10

100

1000

10000

100000

0 50 100 150 200 250 300 350 400 450

Processing temperature [ºC]

Mel

t vi

scos

ity [

Pa·

s]

epoxyvinylester

polyester

PMMA

PA-6

PBT

PA-12

PEK

ETPUPC

PMMAPA-12

PA-6

PBTPPS

PES

PEI

PEEK

PEKK

Reactive processing of thermoset resins

Reactive processing of thermoplastic resins

Melt processing of thermoplastic polymers

• Selection of resin:• Low processing

temperature

• Low viscosity

• Low price/performance


Alternative blade manufacturing

technology


What is done on material development?

• Polymer chemistry and physics

• Resin infusion process

• Composite properties

σσσσ

εεεε


Polymer chemistry and physics

• Resin composition

0

20

40

60

80

100

0 5 10 15 20 25 30 35 40

time [min]

Degre

e o

f conve

rsio

n [%

] .

Fast system

Slow systeminfusion

cure CAPROLACTAM

ACTIVATOR C20 INITIATOR C1



• Resin constitution• Identify important parameters• Understand & simulate the reaction

Polymerisation at different temperatures and compar ison with pure ε-caprolactame, inner temperature record, same beginning

0

50

100

150

200

250

0 200 400 600 800 1000 1200 1400 1600 1800 2000

time [s]

tem

pera

ture

[°C

]

pue CL, 140°C, 1.measur.

140°C, 1.measurement150°C, 1.measurement

160°C, 1.measurement

pure CL, 150°C, 1.measur.pure CL, 160°C, 1.measur.

160°C 150°C140°C



• Resin constitution• Identify important parameters• Understand & simulate the reaction• Characterise the properties• Comparison with currently used material

σ2

σ1

0.1

σσσσ

εεεε0.2 εεεεf

σσσσm

Compared to injection molded PA-6

Condition Young’s modulus [GPa]

Maximum strength [MPa]

Strain at failure [%]

23ºC, dry 4.2 (+ 41%) 96 (+ 14%) 9 (-) 23ºC, 50% RH 2.1 (+ 59%) 61 (+ 4%) 28 (-)

80ºC, dry 1.6 (+ 65%) 51 (+ 32%) 29 (-)


Resin infusion process

• Development of resin infusion process:• Fabric (fine and coarse weave)

• Glass

• UD

• Glass

110°C

110°C

160-180°C

60 minutes

250 mbar



• Development of resin infusion process• Homogeneous properties:

• In flow direction

• Through thickness

135

140

145

150

155

160

165

170

175

0 5 10 15 20 25

Time [min]

Tem

pera

ture

[°C

]

Tmould = 160°C (inlet)

Tmould = 160°C (center)Tmould = 160°C (outlet)

Outlet Inlet

-5

0

5

10

15

20

25

30

35

40

45

135 140 145 150 155 160 165 170 175 180 185

Temperature (ºC)

Laye

r Thermofoil+CarbonCarbonResistiveThermofoilPlated press



• Development of vacuum infusion process• Homogeneous properties• Identify important parameters• Optimise infusion process• Good mechanical properties

• Good fibre-to-matrix bond

10

20

30

40

50

60

70

80

140 150 160 170 180 190 200

Mould temperature [°C]

Inte

rlam

inar

sh

ear

stre

ng

th [

MP

a]

APA-6 composite (unsized/outlet)

APA-6 composite (sized/outlet)


Composite Properties

• Static properties (Dry conditioned)

0

100

200

300

400

500

600

Compressive strength Tensile strength Shear strength

[MP

a]

APA-6 Epoxy PA-6

0

5

10

15

20

25

30

Compressive modulus Tensile modulus Shear modulus

[GP

a]

APA-6 Epoxy PA-6In dry state, APA-6 outperforms

all other reference material



• Static properties (moisture conditioned):

0

50

100150

200

250

300

350

400

450

500

Compressive strength Tensile strength Shear strength

[MP

a]

APA-6 Epoxy PA-6

0

5

10

15

20

25

30

Compressive modulus Tensile modulus Shear modulus

[GP

a]

APA-6 Epoxy PA-6



• Dynamic properties: • APA-6 composite

manufactured at 180C has

better fatigue properties

than the melt processed PA-

6 composite:

• Same toughness

• Higher interfacial bond

strength0

50100150200250300350400

1.0E+

02

1.0E+03

1.0E+

04

1.0E+

05

1.0E+06

1.0E+

07

n

S [M

Pa]

APA-6 (180ºC)PA-6EpoxyLog. (Epoxy)


Conclusions

• For rib/spar/skin-structures, thermoplastic composites are favoured over thermoset composites. Parts can be rapidly melt processed and assembled through welding. Blades will be fully recyclable.

• Vacuum infusion of thermoplastic composites is introduced to overcome the classical drawbacks of these materials.

• The cure of a semi-crystalline thermoplastic resin is more complicated than of a thermoset resin.

• AP Nylon® has a low viscosity (10 mPa.s), good availability, a low price (2-3 €/kg), and a relatively low processing temperature (150-180°C).


Conclusions• Homogeneous composites were obtained after optimisation of infusion process. Temperature, pressure and time are the key parameters.

• Reactively processed PA-6 outperforms melt processed PA-6 in all temperatures and humidities tested.

• Static properties of APA-6 composites are better than of their HPA-6 and epoxy counterparts in dry conditions. When moisture conditioned, the performance of APA-6 composites drops rapidly.

• Reactive processing of thermoplastic composites results in a strong interfacial bond strength and leads consequently to better fatigue performance compared to melt processing.


Vacuum infused thermoplastic

composites for wind turbine blades

Questions?

Julie Teuwen

Delft University of TechnologyFaculty of Aerospace Engineering

Design and Production of Composite Structures

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Vacuum infused thermoplastic composites for wind turbine ... · Thermoplastic wind turbine blades 9...

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