Vacuum infused thermoplastic composites for wind turbine blades

Transcription

1 Vacuum infused thermoplastic composites for wind turbine blades Julie Teuwen, Design and Production of Composites Structures Delft University of Technology Challenge the future

2 Introduction WIND ENERGY: Promising renewable energy source Fast growing market share in energy supply WIND TURBINE BLADES: Length > 50 m Life expectancy 20 years 2

3 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 m blade (R blade )

4 Current blade manufacturing technology Material: Glass fibres (NCF s) Thermoset resin Process: Vacuum infusion Prepregging Design: 2 skins and 1 spar Structural bonding Design Process Material 4

5 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 5

6 Why thermoplastics? Rubber press Processing: Forming Assembly by welding Properties: Good impact properties Pre-cut laminate sheet material Infra red heating panels High toughness, also at low temperatures Abrasion resistant Chemical resistant Life cycle: Unlimited shelf-life of raw materials Short production cycle time Fully recyclable Heating element Clamp connection Welded parts Rubber die Metal die Final thermoplastic composite part Voltmeter Ampmeter 6

7 What still stands in the way? Costs: Technology costs: New technologies and expensive equipment Material costs: Need for intermediates Traditional Processing of Thermoplastic Composites Granules Film Monomer Polymer Powder Solution Processing: High processing temperatures (>200 C): High costs, thermal stresses Melt pressing technology: Laminate Final product Prepreg Limits part size and thickness Properties: Fatigue performance: Weak fiber-to-matrix bond 7

8 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 8

9 Vacuum infusion of thermoplastic composites Selection of resin: Low processing temperature ( C) Low viscosity (10 mpa.s) Low price/performance (2-3 /kg) Anionic Polyamide-6: AP-Nylon World wide availability Melt viscosity [Pa s] ,1 0,01 0,001 PMMA PES PEEK PA-12 PEKK Melt processing of PA-6 PEI thermoplastic polymers PBT PPS Reactive processing of thermoset resins vinylester epoxy polyester PMMA PC ETPU PEK PBT PA-6 PA-12 Reactive processing of thermoplastic resins Processing temperature [ºC] 9

10 Alternative blade manufacturing technology 10

11 What is done on material development? Polymer chemistry and physics σ Resin infusion process ε Composite properties 11

12 Polymer chemistry and physics Resin composition Degree of conversion [%] cure Fast system infusion Slow system ACTIVATOR C20 CAPROLACTAM INITIATOR C1 time [min] 12

13 Polymer chemistry and physics Resin constitution Identify important parameters Understand & simulate the reaction 250 Polymerisation at different temperatures and comparison with pure ε-caprolactame, inner temperature record, same beginning C 150 C 140 C temperature [ C] pue CL, 140 C, 1.measur. 140 C, 1.measurement 150 C, 1.measurement 160 C, 1.measurement pure CL, 150 C, 1.measur. pure CL, 160 C, 1.measur time [s] 13

14 Polymer chemistry and physics σ σ m Resin constitution Identify important parameters Understand & simulate the reaction Characterise the properties Comparison with currently used material σ 2 σ ε f ε 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 (-) Compared to injection molded PA-6 14

15 Resin infusion process Development of resin infusion process: Fabric (fine and coarse weave) Glass UD Glass 110 C C 60 minutes 110 C 250 mbar 15

16 Resin infusion process Development of resin infusion process Homogeneous properties: In flow direction Through thickness Temperature [ C] Outlet Inlet Time [min] Tmould = 160 C (inlet) Tmould = 160 C (center) Tmould = 160 C (outlet) Layer Temperature (ºC) Thermofoil+Carbon Carbon Resistive Thermofoil Plated press 16

17 Resin infusion process Development of vacuum infusion process Homogeneous properties Identify important parameters Optimise infusion process Good mechanical properties Good fibre-to-matrix bond 80 Interlaminar shear strength [MPa] APA-6 composite (unsized/outlet) APA-6 composite (sized/outlet) Mould temperature [ C] 17

18 Composite Properties 600 Static properties (Dry conditioned) [MPa] Compressive strength Tensile strength Shear strength APA-6 Epoxy PA [GPa] In dry state, APA-6 outperforms all other reference material 0 Compressive modulus Tensile modulus Shear modulus APA-6 Epoxy PA-6 18

19 Composite Properties Static properties (moisture conditioned): [MPa] [GPa] Compressive strength Tensile strength Shear strength 0 Compressive modulus Tensile modulus Shear modulus APA-6 Epoxy PA-6 APA-6 Epoxy PA-6 19

20 Composite Properties S [MPa] Dynamic properties: APA-6 (180ºC) PA-6 Epoxy APA-6 composite manufactured at 180C has better fatigue properties than the melt processed PA- 6 composite: Same toughness Higher interfacial bond strength 1.0E E E E E E+07 n 20

21 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 ( C). 21

22 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. 22

23 Vacuum infused thermoplastic composites for wind turbine blades Questions? Julie Teuwen Delft University of Technology Faculty of Aerospace Engineering Design and Production of Composite Structures 23