DELIVERING SOLUTIONS | TRANSFORMING MARKETS | ENHANCING LIVES
Tom DeMint, Dave Hartman, Georg Adolfs
Vacuum Infusion for Wind Blade Manufacturing
Composites & Polycon 2006
Abstract• Vacuum infusion (VIP) is currently used by many blade
manufacturers– 70% glass fiber/resin weight fractions
• Aspects of the VIP process can bring certain fabrication challenges unique to blades,
– Glass fabric placement– Fabric and fiber orientation control– Joint fabrication
• Let’s examine some of those challenges – Enhance blade structural reliability
What is Vacuum Infusion Processing (VIP)?
Airtight MoldAirtight Mold
Vacuum lineVacuum line(P = 0 Atm)(P = 0 Atm)
Vacuum bagVacuum bag
Vacuum bagVacuum bagsealantsealant
Resin line (inlet)Resin line (inlet)P = 1P = 1 AtmosphereAtmosphere
Resin flowResin flow
Fabric, MatFabric, Mat ReinforcementReinforcement
Porous flowPorous flowmediamedia D'Arcy's Law
Peel Peel plyply
Porous flow mediaPorous flow media
Why use VIP for Wind Blades?
• Better Mechanical Properties, Lower weight vs. Hand Layup
– Higher Fiber Content, Strength, Modulus vs. Hand Layup. – Typical VIP Wf > 70% (54% Vf)– Typical HLU Wf < 50% (30% Vf)
• Better reliability– Repeatable processing – Lower property variation – Increases reliability– Reduced Maintence
• Less resin usage– Resin prices are increasing
D’Arcy’s Law of Porous Flow
∆P (Reinforcement Permeability)~~Resin Flow Rate
(Resin viscosity) (flow distance)
∆P (Pressure Drop) = 1 atm (sea level)Resin viscosity < 150 cp (tool temperature)Flow distance: ½ - 1/3 chord length
Reinforcement porosity and permeability influenceresin infusion fill rate
Closed Molding Process Flavors
Process and Fabric choice affects part cycle timeLarge
Small
Part
Siz
e
LowHighVolume, Tooling Cost
• Marine Hull and Deck• Defense Vehicle
Infusion time: 2-90 min.
• Marine Components• Auto Components
Infusion time: 3-50 min.
• Truck Components• Auto Components
Infusion time: 0.5-50 min.
Lite - RTM RTM
CCBMVIP• Marine Hull and Deck• Wind Turbine Blades• RV Side PanelsInfusion time: 5-180 min.
400 parts/year
Vacuum Infusion for Larger Structures RTM for Small Complex Structures
F ib e r g la s s B o a ts L e n g th E v o lu t io n
0 %
5 %
1 0 %
1 5 %
2 0 %
2 5 %
3 0 %
3 5 %
1 9 9 7 1 9 9 8 1 9 9 9 2 0 0 0 2 0 0 1 2 0 0 2
Mar
ket S
hare
1 4 ' a n d u n d e r 1 4 ' to 1 6 '1 1 '' 1 7 ' to 1 7 '1 1 "1 8 ' to 1 8 '1 1 " 1 9 ' to 2 0 '1 1 " 2 1 ' a n d o ve r
Large Wind Blade Manufacturing Evolution to VIP
05
101520253035404550
1990 1995 2000 2005 2010Approximate Year
Bla
de L
engt
h - M
eter
s
Resin InfusionWet LayupResin Transfer MoldingInjection Molding
Vacuum Infusion Tooling is Simple
• VIP equipment for small parts
• Tooling conversion from Open to Closed Molding
Spray-up Tool
6 inches +
Attach Flange
Vacuum tight
O
Technical Flange Detail is Very Important forProper Vacuum Consolidation
Vacuum Bag
Bag Sealant
Peel Ply
Reinforcement Extended Flange for VIP Bag seal
Joint must be air tightHLU tool
6 inches
Modifying HLU tooling can be tricky
Process Comparison Cost Model
Labor+Overhead, $549.97
Labor+Overhead, $274.98 Labor+Overhead, $277.45
Reinforcements, $88.49
Reinforcements, $189.58 Reinforcements, $182.58
Resin+Gel Coat, $64.01
Resin+Gel Coat, $83.13 Resin+Gel Coat, $75.41
Tooling, $44.00
Tooling, $99.00
Tooling, $24.20
Total, $746.47
Total, $646.69
Total, $559.64
$0.00
$100.00
$200.00
$300.00
$400.00
$500.00
$600.00
$700.00
$800.00
Open Mold RTM Infusion
Part
Cos
t
$0.00
$100.00
$200.00
$300.00
$400.00
$500.00
$600.00
$700.00
$800.00
Example for a 5 meter length boat, production volume of 2 per day
Improvements in Fabric Design on Resin Flow Rate and Quality
0
5
10
15
20
25
30
35
40
45
50
0 1 2 3 4 5 6Infusion Time (minutes)
Res
in In
fusi
on F
low
Dis
tanc
e, in
Heated Mold
ReinforcementPermeability
InfusionMedia Channels
Resin Viscosity
FlowTex™
Integrated Flow Channels(Path of Resin Transfer)
Integrated Flow Channels(Path of Resin Transfer)
Which type of Flow Media applies?
• Surface medium:– Suitable for small series– Weight-critical
• Pros: • Use of existing tooling• Easy for complex parts• Light weight, high-fiber volume parts
• Cons:• Adds installation labor• Added cost of disposable flow media and resin• Generates waste
Which type of Flow Media applies?
• Grooved Core:– Weight/Stiffness-Critical
• Pros:– Fast resin flow– No additional flow media required– Works for VIP and RTM Lite
• Cons– Works only for cored laminates– Adds 3 to 7 % weight to the part– Not inexpensive
Which type of Flow Media applies?
• Interlaminar– Cost-critical
• Pros:– Integral to the part– Adds thickness at low fiber Wf– Works in VIP and RTM Lite
• Cons– Adds resin weight
Part Size and Complexity Requires Improvements in Materials and Processes• Reduced Fabric Misalignment with Good Conformability • Faster and More Consistent Resin Infusion • Proper Training of Resin Infusion Techniques • Automated Resin Delivery and Pre-forming of Fabrics
Used by Permission Owens Corning Used by Permission TPI
Methods to Enhance Blade Reliability
• Unidirectional Fabrics– Knits: Use Tricot stitch
type, high stitch count
Methods to Enhance Blade Reliability
• UD Fabrics– Woven: A-style fabrics. Hot melt leno locks rovings.
Methods to Enhance Blade Reliability
• Manufacturing Details– No fabric bridging
– Stagger ply drops
Vacuum Bag pleat
Personnel: VIP Training, Process Discipline
• Biggest issue– CHANGE
• Implementation approaches:– Key team selection– Training
Summary: “Go with the Flow”
• Closed Molding is spreading as cost effective processes that enable the growth of composites
• New types of Fabrics, reinforcements and process aids are emerging to help the Wind Energy market as it grows
• As Wind market grows, biggest challenge may be in finding, training, and retaining skilled VIP labor
DELIVERING SOLUTIONS | TRANSFORMING MARKETS | ENHANCING LIVES