Vacuum Infusion For Wind Blade Manufacturing - OCV ...

Vacuum Infusion for Wind Blade
Manufacturing
Tom DeMint, Dave Hartman, Georg Adolfs
Composites & Polycon 2006
DELIVERING SOLUTIONS | TRANSFORMING MARKETS | ENHANCING LIVES

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)?
Porous flow
media
Vacuum line
(P = 0 Atm)
D'Arcy's Law
Vacuum bag
Peel ply
Fabric, Mat Reinforcement
Resin line (inlet)
P = 1 Atmosphere
Porous flow media
Vacuum bag
sealant
Airtight Mold
Resin flow

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
Resin Flow Rate
~
∆P (Reinforcement Permeability)
(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 influence
resin infusion fill rate

Closed Molding Process Flavors
Large
Process and Fabric choice affects part cycle time
Part Size
VIP
• Marine Hull and Deck
• Wind Turbine Blades
• RV Side Panels
Infusion time: 5-180 min.
CCBM
• Marine Hull and Deck
• Defense Vehicle
Infusion time: 2-90 min.
Lite - RTM
• Marine Components
• Auto Components
Infusion time: 3-50 min.
RTM
• Truck Components
• Auto Components
Infusion time: 0.5-50 min.
Small
Low
400 parts/year
Volume, Tooling Cost
High

CARTM TM (Channel-Assisted RTM)

Vacuum Infusion for Larger Structures
RTM for Small Complex Structures
Fiberglass Boats Length Evolution
35%
30%
25%
Market Share
20%
15%
10%
5%
0%
1997 1998 1999 2000 2001 2002
14' and under 14' to 16'11'' 17' to 17'11"
18' to 18'11" 19' to 20'11" 21' and over

Large Wind Blade Manufacturing Evolution to VIP
Blade Length - Meters
50
45
40
35
30
25
20
15
10
5
0
Resin Infusion
Wet Layup
Resin Transfer Molding
Injection Molding
1990 1995 2000 2005 2010
Approximate Year

Vacuum Infusion Tooling is Simple
• VIP equipment for small parts
O
• Tooling conversion from
Open to Closed Molding
6 inches +
Attach Flange
Spray-up Tool
Vacuum tight

Technical Flange Detail is Very Important for
Proper Vacuum Consolidation
Vacuum Bag
Bag Sealant
Peel Ply
Reinforcement
Extended Flange for VIP Bag seal
HLU tool
Joint must be air tight
6 inches
Modifying HLU tooling can be tricky

Vacuum Infusion -Low Capital Investment

Process Comparison Cost Model
$800.00
Total, $746.47
$800.00
$700.00
Tooling, $44.00
Resin+Gel Coat, $64.01
Total, $646.69
$700.00
$600.00
Reinforcements, $88.49
Tooling, $99.00
Total, $559.64
$600.00
Part Cost
$500.00
$400.00
$300.00
Labor+Overhead, $549.97
Tooling, $24.20
Resin+Gel Coat, $83.13 Resin+Gel Coat, $75.41
Reinforcements, $189.58 Reinforcements, $182.58
$500.00
$400.00
$300.00
$200.00
$200.00
$100.00
Labor+Overhead, $274.98 Labor+Overhead, $277.45
$100.00
$0.00
Open Mold RTM Infusion
Example for a 5 meter length boat, production volume of 2 per day
$0.00

Improvements in Fabric Design on Resin Flow Rate and
Quality
Resin Infusion Flow Distance, in
50
45
40
35
30
25
20
15
10
5
0
Heated
Mold
Infusion
Media
Channels
Reinforcement
Permeability
Resin
Viscosity
0 1 2 3 4 5 6
Infusion Time (minutes)

Trends in Fabrics for Resin Infusion
• Woven Architecture
• Knitted Architecture

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:
• Cons:
• Use of existing tooling
• Easy for complex parts
• Light weight, high-fiber volume parts
• 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

Good Conformability of Single Ply

Orientation of Reinforcement

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

Fiber Alignment in Fabric Design Improves
Compression Fatigue

Correct Fabric and Fiber Alignment is Important
Used by permission of NREL

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
Vacuum Bag pleat
– Stagger ply drops

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