pende

Triboluminescent Sensor for Distributed Damage Monitoring

in Composites: Wind Turbine Blade Application

Figure 8. No degradation in TL signals from ITOF sensor after 100 impact loading

cycles at same point on the sensor and after over 800 impact loads along a sensor

TiO2 coated CNT

yarn

CNT yarn

a)

Problem

Global growth in wind power capacity is fueled by the need for green energy and

energy independence.

The Need

Increasing safety & cost-effectiveness of wind energy

by creating composite structures with in-situ damage monitoring capabilities from cradle to grave

Figure 1. Global cumulative installed wind capacity (Source: Global World Energy Council)

• More installed capacity, more accidents

• #1 cause of accident: wind blade failure

• Causes of wind blade failure: poor maintenance & fire from lightning

• Insurance claim: $240,000/wind blade failure

• Wind energy responsible for large portion of $200 Million claims paid by GCube

in (2008-2012)

• Existing sensors & condition monitoring focus only on gears & electrical systems

• Damage detection in blade primarily by inspection: high cost, high risk, low

frequency, poor maintenance

Figure 2. Wind turbine accidents per year (Source: Caithness Windfarm Information Forum)

• Cost-effective in-situ damage monitoring sensor system for large composite

structures like wind turbine blades and airplanes

Objectives

• Investigate durability of ITOF sensor under repeated loading

• Fabricate carbon fiber reinforced polymer (CFRP) with integrated ITOF sensor

(ITOF-CFRP)

• Demonstrate in-situ and distributed damage monitoring capability in ITOF-

CFRP

Results

Bio-inspired solution: ITOF Sensor

• Benefits: Early damage detection, timely repairs, reduced accidents & casualty,

reduced downtime & maintenance cost

• Uniqueness: No need for external light source or complex & expensive

interrogation systems, easier damage identification & no data overload

• Application: Bridges, wind turbine blades, aircrafts

Durability test: direct impact loading on ITOF sensor

0.00

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0 10 20 30 40 50 60 70 80 90 100

TL s

ign

al (

AU

)

Number of impacts

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act

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(N

)

Number of impacts

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)

Number of impacts

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)

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(N

)

Number of impacts

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0 10 20 30 40 50 60 70 80 90 100

Imp

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load

(N

)

Number of impacts

a1)

a2)

b1)

b2) c2)

c1)

a)b)c)d)

a’)

a’’)

b’) c’)

b’’) c’’)

a)

d)

e)

b)

c)

f)

a)

a’)

a’’)

b)

b’)

b’’)

a) b)

c)

Figure 6. Scanning electron

micrographs of ITOF sensor with

30% wt ZnS:Mn triboluminescent

composite film a) cross-section, b)

random dispersion of ZnS:Mn in

polymer matrix, c) closer view of

ZnS:Mn crystals with fracture lines

on surfaces

0

0.1

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50 100 150 200 250 300 350

TL s

ign

al (

AU

)

Impact load (N)

0

0.1

0.2

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50 75 100 125 150 175

TL s

ign

al (

AU

)

Impact load (N)

a) b)

Figure 9. a) Sensor with 30 wt% ZnS:Mn and b) 50 wt% ZnS:Mn exhibit linearity between sensor response and

impact load; 50 wt% sensor exhibits higher sensitivity (0.0033) than 30 wt% sensor (0.0018)

Comparison of two sensor configurations

Composite with damage-sensing ability

Figure 10. ITOF-CFRP test panel fabrication a) Fiber lay up,

b) Integration of ITOF sensor using a weave method,

c) Completion of fiber layup, d) Vacuum bagging, e) Composite part fabrication

with vacuum assisted infusion

Figure 11. Experimental setup for low velocity impact test on

ITOF-CFRP composite panel

a) Black box housing photomultiplier tube (PMT), b) Power

supply, c) ITOF sensor from composite panel connected to

PMT, d) Impactor with load cell, e) ITOF-CFRP composite

panel, f) Infrared camera (FLIR) system

Figure 12. Successful sensing of multiple impact events at multiple

locations in ITOF-CFRP a) First impact location, b) Second impact location,

c) Third impact location; d) Position of integrated ITOF sensor in composite

panel; a’) TL signal detected during first impact event; b’) TL signal detected

during second impact event; c’) TL signal detected during third impact event;

a’’) Impact load detected during first impact event; b’’) Impact load detected

during second impact event; c’’) Impact load detected during third impact

event.

Conclusion and Future Work • ITOF sensor produced repeatable and sustained response after 100 impact

cycles at a location and over 800 impact cycles on a single sensor strip

• Successfully integrated the ITOF sensor in CFRP to create composite with self-

sensing capability and demonstrated capability to detect barely visible impact

damage

• Future work to focus on sensor size reduction to ~20 μm so it can be easily

woven into carbon or glass fibers during manufacture

• Also create an integrated ITOF sensor with lightning strike protection and

electromagnetic interference (EMI) shielding capabilities

Acknowledgments We thank HPMI for laboratory usage. Funding for this project was provided by the NSF-CMMI-0969413.

Figure 13. Self-sensing of barely visible impact damage in ITOF-

CFRP a) Impacted surface of CFRP composite with integrated ITOF

sensor with 30% (wt) ZnS:Mn content showing barely visible impact

effect/damage, a’) Corresponding TL signal detected by ITOF

sensor at the instant of impact of drop weight with composite plate,

a”) Commencement of damage in composite caused by the impact

as detected by FLIR infra red camera, b) Impacted surface of CFRP

composite with integrated ITOF sensor with 50% by weight ZnS:Mn

content showing barely visible impact effect/damage, b’)

Corresponding TL signal detected by ITOF sensor at the instant of

impact of drop weight with composite plate, b”) Commencement of

damage in composite caused by the impact as detected by FLIR

infra red camera

Figure 3. Difficulty of access for maintenance crews (Source: www.offshorewind.biz;

http://www.texasenterprise.utexas.edu/article/alternative-energy-grid-faces-logistical-

challenges)

David O. Olawale, Emily Hammel, Tarik J. Dickens, Okenwa I. Okoli High Performance Materials Institute, FAMU-FSU College of Engineering/Nanotechnology Patronas Group Inc.; okoli@eng.fsu.edu

Figure 5. a) Representation of human body nervous system to be mimicked by ITOF sensor (Source: http://www.humanbody.dke-explore.com/clipart/human/image/exp_human042.jpg)

b) Schematic of ITOF sensor integration into CFRP to provide in-situ damage sensing in wind turbine blades

a)

c)

b)

Triboluminescence Sensory Receptor (TSR)

Polymer optical fiber (POF)

POF with jacket

Figure 7. Experimental setup for

automated impact test

a) Automated impact hammer,

b) ITOF sensor made into a loop

for double-end coupling into PMT,

c) Photomultiplier tube enclosure

Purpose

• Develop smart composites with in-situ and distributed damage monitoring

capability from cradle to grave by utilizing the bio-inspired and proprietary In-

situ Triboluminescent Optical Fiber (ITOF) sensor

a) b)

Towards Composite Structures with In-situ Damage Sensing Capability

Figure 4. Schematic of the ITOF sensor’s components

a) b) c)

d)e)