Sandia National Laboratories developed advanced nondestructive inspection (NDI) methods for composite wind turbine blades to detect manufacturing flaws. They created a test specimen library with engineered defects and worked with industry to evaluate technologies. Methods like phased array ultrasound and pulsed thermography were optimized for blade materials and designs. On-site testing at manufacturing facilities demonstrated the ability to automatically detect voids and disbonds. The goal is to help manufacturers find flaws before blades leave the factory to improve reliability.

1. Stephen Neidigk
Dennis Roach, Randy Duvall, Tom Rice
Sandia National Labs
August 14th, 2013
2013 Wind Plant Reliability Work Shop
Evolution and Technology Transfer of Advanced Inspection
Methods for Wind Turbine Blades
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly
owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security
Administration under contract DE-AC04-94AL85000

2. Wind Blade NDI Test
Specimen Library
WINDIE Experiments and
Inspection Results
BSDS 9 Meter Fatigue
Test Blade Inspections
Presentation Overview
On Blade Factory
Testing
Development and Testing of
Automated and Semi-Automated
Phased Array Inspections
How NDI Relates to
Reliability
UT Inspection Methods

3. Objectives
• Produce optimum deployment of automated or semi-automated NDI
to detect undesirable flaws in blades (time, cost, sensitivity)
• Transfer technology to industry through hardware and technology
evaluation, inspector training, and procedure development
Create the ability for manufacturers to determine the
quality of their product before it leaves the factory
Develop
Evaluate
Validate
Transfer
Potential nondestructive
inspection methods for the
detection of flaws in composite
wind turbine blades

4. NDI in the Wind Industry
• Different blade manufacturers use different inspection techniques,
procedures and detection requirements.
• Different blade designs
• Varying manufacturing practices
• Varying materials
Post manufacturing in the plant In the field (up tower)
Not necessarily the same
hardware
Spar Caps & Shear Web Box Spar & Shear Webs

5. Different composite materials and designs, but looking for similar
manufacturing defects:
• Laminate porosity
• Interply disbonds
• Adhesive voids and disbonds
• Contaminates and foreign objects
• In-plane and out-of-plane waves
Early detection of manufacturing flaws
enhances blade reliability
NDI in the Wind Industry
Thick Spar Structure
Thick Adhesive Bond Lines
Balsa or Foam Cores

6. 1 2 3
Spar Cap
Spar cap back wall
Adhesive back wall
Slight Shift
3
2
1
Large Increase in Amplitude
Large Decrease in Amplitude
Example Bond Line Inspection (A-Scan)

7. Example Inspection (2 Dimensional C-Scan)
X-Y Position EncoderA-Scan
C-Scan
High Amplitude
Low Amplitude
Gate

8. Phased Array verses Single Element Transducer
Single Element Transducer
A-Scan
C-Scan
Phased Array with Liner Encoder
B-Scan
A-Scan
16 Elements

9. Sandia Labs Wind Turbine Blade
Test Specimen Library
Additional large samples are housed at the Wind & Airworthiness
Assurance NDI Validation Center (WAANC) hangar
Added carbon sample set

10. NDI Feedback Specimens 1, 2 & 4 –
Shear Web & Foam Core Specimens
Laminate with Waviness
and Dry Regions
Foam Core with Disbonds
and Delaminations
Shear Web/Spar with Disbonds and Delaminations

11. Different Flaw Types Engineered into
NDI Feedback Specimens (Examples)
Glass Beads Grease Pillow InsertMold Release
Materials inserted into multiple layers
Voids in
bond joint
Glass beads
In bond joint
Dry fabric areasWaviness produced
by pre-cured
resin rods and
stacked plies
Pull tabs in
bond joint
Single ply of dry fabric

12. Fabrication of Carbon Feedback Specimens and
NDI Reference Standards at TPI
Flaws were placed at varying depths
and locations using a template
Line of various flaws at same depth
Spar caps prior to bonding of
shear web
Blade assemblies developed for
bond line inspection

13. Different Flaw Types Engineered into Carbon
NDI Feedback Specimens (Examples)
Dry Areas –
Removed Resin
Pillow Insert Grease Contamination
Pre-Preg Backing
Carbon Fuzz Ball
Fiberglass
FOD
Adhesive Void
Glass Microballoons
in Bond Line
Pull Tab Disbonds

14. Completed Carbon Feedback Specimens & NDI Ref Stds
The set of specimens will be used to:
• Develop and test NDI technology
• Train inspectors and familiarize them with
carbon material
• Calibrate and set up NDI equipment
• Ultrasonic flaw signal characterization
• Inspection procedure development

15. Carbon Pre Preg Spar Inspection Challenges
A-scan 40 mm. thick Fiberglass
Gain – 55.2 dB
Back Wall
Increase gain to
achieve 80% FSH
Noise
A-scan 40 mm thick Carbon Pre-Preg
Gain – 55.2 dB
200x magnification
A-scan 40 mm Carbon Pre-Preg
Working with material manufacturers to
ensure inspectability of their product
Gain – 65.5 dB

16. Carbon Wind Blade Specimen Characterization
C-scan produced by Omniscan Unit 1.5L16
(1.5 MHZ) 40mm Water Box REF-BLK-C2-TPI
75%75%75%
CSPIFBH
75%
GREASE
75%
PB
75%
PT
75%
BOND
25%
BOND INT 1INT 2
PTPTFBHFBH
Gate 1: Spar Cap and Adhesive Shear Web Gate 2: Adhesive Shear Web

17. CH1
CH5
CH3 CH6
CH8
CH9
CH10
CH11
CH4 CH7CH2
CH12
CH13
9 Meter Fatigue Test Blade Inspections
Flaw Location/Type Identifier

18. 9 Meter Blade Inspections (pre-fatigue)
Note: Significant
noise in signals
(visible porosity)
Flaw signals showing through noise
Balsa Wood
Shear Web Area
Balsa Wood
Inspections Included:
MAUS V Pulse Echo UT
Pulse Echo A-Scan Capture (over 500)
OmniScan Phased Array
Pulsed Thermography
Vibro Thermography (Resodyne)
Millimeter Wave Inspection Tool (POC)
Laser Shearography (LTI)
RotoArray Phased Array (GE)

19. WINDIE & 9 Meter Blade Inspections–
Recent Inspections
Physical Optics Corporation – Millimeter Wave Inspection Device
Pillow Insert Detected
in BSDS Blade

20. WINDIE & 9 Meter Blade Inspections –
Recent Inspections
Olympus - Phased Array Ultrasonics
Full length scan capability
Curvature Inspection
Challenge

21. GE RotoArray –
1 MHz Rolling Phased Array
WINDIE & 9 Meter Blade Inspections –
Recent Inspections
Ultrasonic C-Scan of 2.25 inch thick feedback specimen
Ultrasonic B-Scan of fiberglass 9 meter blade
Spar Cap
Back Wall
Adhesive/Spar
Cap Back Wall
As deployed on
Omniscan vs.
GE Phasor

22. Fatigue Test Blade Prior to Failure Inspections
Inspections templates used to
relocate the exact point where the
initial measurements were taken.
Out of plane wave at 3750 mm on the
HP side induced:
• Large delamination the width of the
spar cap
• Cracks perpendicular to the spar in
the matrix

23. 24G-HP-OPW-SC-3750-18-A
A BD
C
24G – C Pre
24G – D Pre
24G – C Post
24D – D Post
Signal Shift and
Amplitude Decrease
Signal Shift and
Amplitude Decrease

24. 75% (ON
PLIES 9-11)
50% (ON
PLIES 19-21)
25% (ON
PLIES 29-31)
INTERFACE 1
AA
B B
2.00" DIA
1.00" DIA
50% (ON
PLIES 19-21)
25% (ON
PLIES 29-31)
75% (ON
PLIES 9-11)
2.00" DIA
1.00" DIA
1.65" DIA
1.15" DIA
1.00" DIA
2.50" DIA 2.50" DIA
1.00" DIA
2.50" DIA
1.00" DIA
2.00" DIA 2.00" DIA
2.50" DIA
1.00" DIA 1.00" DIA
2.00" DIA 2.00" DIA
2.00" DIA
2.00" DIA
2.50" DIA
1.00" DIA
2.50" DIA
INTERFACE 2
Probe Frequency & Type Analysis
500 KHZ vs. 1 MHz Contact vs Focused
Spar Cap = 2.14” th
Adhesive Bond Line = 2.65” th.
Balancing
Clarity with
Depth of
Penetration
500 KHz Contact1 MHz Contact
1 MHz Focused Probe

25. Gate Setting Analysis
MAUS V 500 KHZ Contact Test C-Scan Results
Defects at the shear web flange and adhesive layer may, or may
not, be detected depending on gate settings and part thickness.
Adhesive
Back Wall
Laminate and
Adhesive Back Wall

26. Probe Housing Development for Factory Deployment
Sandia has focused on two water box deployment options:
• Adjusts to slight curvature surfaces
• Maximizes signal strength
• Accommodates necessary standoffs for signal clarity
• Easily saves scanned images for reference using the
unidirectional Mouse encoder
• Either sealed or pierced bladder construction
4 Ply Pillow Inserts
FBH
FHB’s Pillow Inserts

27. On-Blade Testing in Manufacturing Facility
36 Meter Station
Scanning Direction
Higher
Amplitude
Scan Area
Spar Cap Back Wall
Adhesive Back Wall

28. On-Blade Testing in Manufacturing Facility
16 Meter Station on
Fiberglass Spar Cap Blade
Spar Cap Cross Section Schematic
Showing the Spar Cap, Adhesive
Bond Line and Shear Webs
Scanning Direction
Vertical Strip C-Scan Image
Showing Adhesive Void in
Upper Bond Line
Adhesive Void
Between Spar
Cap and
Shear Web
Sealed water box and 1.5L16 Phased Array probe was used to
detect missing adhesive in bond lines

29. Wind Blade NDI Program Results at Sandia
NDI Test Specimen Library including:
• Full-scale test specimens
• Fiberglass and carbon specimens with engineered defects ranging in
thickness up to 2.5 inches
• Feedback specimen and reference standard development
• Statistically valid, blind probability of detection experiment
Developing enhanced NDI methods for wind blades
• Improved signal to noise and image resolution (improved flaw detection)
• Factory deployment
Evaluation of various NDI technologies on standardized specimen set
(WINDIE – worked with 22 different NDI developers)
• Assessment of multiple methods to comprise NDI tool box
Early detection of manufacturing flaws
enhances blade reliability

30. Stephen Neidigk
Sandia National Labs
(505)284-2200
sneidig@sandia.gov