Stephen NeidigkDennis Roach, Randy Duvall, Tom Rice

Sandia National Labs August 14th, 2013

2013 Wind Plant Reliability Work ShopEvolution 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

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

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

DevelopEvaluateValidateTransfer

Potential nondestructive inspection methods for the detection of flaws in composite wind turbine blades

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

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

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)

Example Inspection (2 Dimensional C-Scan)

X-Y Position EncoderA-Scan

C-Scan

High Amplitude

Low Amplitude

Gate

Phased Array verses Single Element Transducer

Single Element Transducer

A-Scan

C-Scan

Phased Array with Liner Encoder

B-Scan

A-Scan

16 Elements

Sandia Labs Wind Turbine BladeTest Specimen Library

Additional large samples are housed at the Wind & AirworthinessAssurance NDI Validation Center (WAANC) hangar

Added carbon sample set

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

Different Flaw Types Engineered into NDI Feedback Specimens (Examples)

Glass Beads Grease Pillow InsertMold ReleaseMaterials 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 inbond joint

Single ply of dry fabric

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

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

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

Carbon Pre Preg Spar Inspection Challenges

A-scan 40 mm. thick Fiberglass

Gain – 55.2 dBBack 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-PregWorking with material manufacturers to ensure inspectability of their product

Gain – 65.5 dB

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

CH1

CH5

CH3 CH6

CH8

CH9

CH10

CH11

CH4 CH7CH2

CH12

CH13

9 Meter Fatigue Test Blade Inspections

Flaw Location/Type Identifier

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 UTPulse Echo A-Scan Capture (over 500)

OmniScan Phased ArrayPulsed Thermography

Vibro Thermography (Resodyne)Millimeter Wave Inspection Tool (POC)

Laser Shearography (LTI)RotoArray Phased Array (GE)

WINDIE & 9 Meter Blade Inspections–Recent Inspections

Physical Optics Corporation – Millimeter Wave Inspection Device

Pillow Insert Detected in BSDS Blade

WINDIE & 9 Meter Blade Inspections –Recent Inspections

Olympus - Phased Array Ultrasonics

Full length scan capability

Curvature Inspection Challenge

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

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

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

75% (ON PLIES 9-11)

50% (ONPLIES 19-21)

25% (ONPLIES 29-31)

INTERFACE 1AA

B B

2.00" DIA

1.00" DIA

50% (ONPLIES 19-21)

25% (ONPLIES 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 Analysis500 KHZ vs. 1 MHz Contact vs Focused

Spar Cap = 2.14” thAdhesive Bond Line = 2.65” th.

Balancing Clarity with

Depth of Penetration

500 KHz Contact 1 MHz Contact

1 MHz Focused Probe

Gate Setting AnalysisMAUS 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

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

On-Blade Testing in Manufacturing Facility

36 Meter Station

Scanning Direction

Higher Amplitude

Scan Area

Spar Cap Back WallAdhesive Back Wall

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

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

Stephen NeidigkSandia National Labs(505)284-2200sneidig@sandia.gov