Boeing 787 Composite Structures - BRIDGE ... by Boeing Smart Composite System Laboratory The Universit y of Tok o Feb. 2005, Newton Composite Materials and Structures are most important

1

Smart Composite System Laboratory The University of TokyoSmart Composite System Laboratory The University of Tokyo

Structural Health Structural Health Monitoring of Aerospace Monitoring of Aerospace

Composite StructuresComposite Structures

Presentation at APSSAugust 2, 2010

Kashiwa Campus, the University of Tokyo

Nobuo TakedaNobuo TakedaThe University of TokyoThe University of Tokyo

Dept. Advanced EnergyGraduate School of Frontier Sciences

andDept. Aeronautics and Astronautics

School of Engineering

Smart Composite System Laboratory The University of Tokyo

Boeing 787

Reusable Launch Vehicleof JAXA/ISAS

Airbus A380

Structural Health Monitoring (SHM) is a key technology for safety assurance and maintenance cost reduction

Increasing Use of Advanced Increasing Use of Advanced Composites in Aerospace StructuresComposites in Aerospace Structures

Courtesy by Airbus

Courtesy by Boeing

to reduce weight for energy saving


Composites50%

Titanium15%

Other5%Steel

10%

Aluminum20%

CFRPCFRPサンドイッチ

GFRPアルミ合金

鋼・チタンエンジンパイロン

複合材

アルミ合金

チタン合金

鋼材その他

Composites50%

Titanium15%

Other5%Steel

10%

Aluminum20%

CFRPCFRPサンドイッチ

GFRPアルミ合金

鋼・チタンエンジンパイロン

複合材

アルミ合金

チタン合金

鋼材その他

Materials Used in Boeing 787 AircraftMaterials Used in Boeing 787 Aircraft

CFRP50%

Al Alloys20%

Ti Alloys15%

Steel10%

Others5%

CFRPCFRP SandwichGFRPAl AlloysSteel & Ti Alloys, Engine Pyron Courtesy by Boeing


Feb. 2005, Newton

Composite Materials and Structures are most important in Japanese aerospace industries

Smart Sensing and Structural Health Monitoring are key technologies for safe operation and efficient

maintenance for future aerospace structures


OutlineOutline(1)(1) Structural Health Monitoring Group,Structural Health Monitoring Group, NEDO Smart NEDO Smart

Material/Structure System Program (FY1998Material/Structure System Program (FY1998--2002)2002)

(2)(2) Structural Integrity Diagnosis and Evaluation of Structural Integrity Diagnosis and Evaluation of Advanced Composite Structures (ACSAdvanced Composite Structures (ACS--SIDE) SIDE) Project,Project, METIMETI Advanced Material & ProcessingAdvanced Material & Processingforfor NextNext--Generation Aircraft Structure ProgramGeneration Aircraft Structure Program(FY2003(FY2003--2007)2007)

(3) Integrated High(3) Integrated High--Resolution Distributed Strain Resolution Distributed Strain Monitoring with Embedded Optical Fibers in Monitoring with Embedded Optical Fibers in Composite Composite StStruructuresctures (FY2007(FY2007--))


Health MonitoringUniv. Tokyo10 Companies

Active/Adaptive Structures

Nagoya Univ.4 Companies

& Tokyo MMU

Smart ManufacturingOsaka City Univ.

2 Companies

Actuator Materials& Devices

Tohoku Univ.4 Companies &

Univ. of Washington

DemonstratorProgram

4 Companies

National Institute of Advanced Industrial Science and TechnologySmart Structure Research Center

METI(Ministry of Economy, Trade and Industry)

NEDO(New Energy and industrial Technology Development organization)

RIMCOF(R&D Institute of Metals & Composites for Future Industries)

5 Year ProgramFrom April 1998To March 2003

Approximately5 Million US

Dollars per year

NEDO Smart Material/Structure System ProgramNEDO Smart Material/Structure System Program

2


Typical Damages in Composite LaminatesTypical Damages in Composite Laminates

Small-diameter FBG sensors were developed for detection of transverse cracks or the delamination in CFRP laminates.

Transverse Cracks

Delaminations

Typical Thickness of CFRP PrepregLayers: 125 μm

Diameter of Carbon Fiber: 5-8 μm


Ref

ract

ive

Inde

x

10mm0.53μm

Polyimide CoatingCladding

Core

6.5μm40μm

52μm

SmallSmall--diameter Fiber Bragg Grating Sensordiameter Fiber Bragg Grating Sensor

FBGCore Cladding


Cladding PolyimideCoating

50μm

0o Ply

90o Ply

Uncoatednormal FBG sensor

Polyimide-coatedsmall-diameter FBG sensor

Cladding: φ 125μm Cladding: φ 40μmPolyimide Coating: φ 52μm

CFRP Laminates with Embedded FBG SensorsCFRP Laminates with Embedded FBG Sensors


Response of FBG Response of FBG Sensor to StrainSensor to Strain

λ0 λ1

IR

Incident Light

TransmittedLight

λ1 d=0.5μm

Reflection spectrum is narrowband.Strain determined from wavelength shift.

Incident Light Transmitted

Lightλ1λ2

λ3

λ0 λ1

IR

λ2 λ3

Reflection spectrum becomes broadband,which can be used for damage detection.

Uniform strain Non-uniform strain

Small-Diameter Optical Fiber

FBG0o Ply

0o Ply90o Ply

Transverse CracksTensile Load

Small-diameter FBG Sensors can be embedded close to transverse cracks without deteriorating the laminate.

λ1=C1d=C2ε


Detection of Transverse CracksDetection of Transverse Cracks

Small-Diameter Optical Fiber

FBG Sensor

CFRP: T800H/3631Laminate configuration: quasi-isotropic [45/0/-45/90]s

GFRP TabA

A

Cross section at A-A50μm

Cladding

Polyimide Coating

90o Ply

-45o Ply

Embedded FBG sensor in –45o ply for detection of 90o transverse cracks


Reflection Spectra at Various Tensile Strain LevelsReflection Spectra at Various Tensile Strain Levels

1551 1555 1553 1557 1553 1559 1553 1559

0.2

0.15

0.1

0.05

0

Ref

lect

ivity

Wavelength (nm)

(A) ε = 0.00%, ρ = 0.0cm-1 (D) ε = 1.10%, ρ = 7.1cm-1

(B) ε = 0.49%, ρ = 0.0cm-1 (E) ε = 1.31%, ρ = 12.7cm-1

(C) ε = 0.90%, ρ = 1.4cm-1

(A) (B) (C) (D) (E)

Crack density ρ vs. tensile strain ε. Reflection spectra measured under tensile loading.

0

5

10

15

0 0.5 1 1.5

Cra

ck D

ensi

ty (

cm-1

)

Strain (%)

(A) (B)(C)

(D)

(E)

Detection of Transverse CracksDetection of Transverse Cracks

Reflection spectrum was sensitively deformed with increase in crack density

3


0

0.2

0.4

0.6

0.8

1

1.2

1548 1550 1552 1554

Nor

mal

ized

Inte

nsity

Wavelength (nm)

Ld = 0mm

No. of Cycles = 0

1548 1550 1552 1554Wavelength (nm)

Ld = 5.2mm

No. of Cycles = 20 x 103

0

0.2

0.4

0.6

0.8

1

1.2

1548 1550 1552 1554

Nor

mal

ized

Inte

nsity

Wavelength (nm)

Ld = 7.4mm


1548 1550 1552 1554Wavelength (nm)

Ld = 9.0mm


Detection of FreeDetection of Free--Edge Edge DelaminationDelamination in Composite in Composite Laminates with Embedded SmallLaminates with Embedded Small--Diameter FBG SensorDiameter FBG Sensor

Intensities of two peaks changed with the delamination growthOptical Loss: 0.4 dB


Impact Damage Impact Damage Detection in Composite StructuresDetection in Composite Structures-- Building Block Approach Building Block Approach --

OPTICAL FIBER

STIFFENED PANEL

FY1998-1999

IMPACT

FY2000-2001 FY2001-2002

Specimen

Impact TestingMachine

SMALL-DIAMETER OPTICAL FIBER

SMALL PANEL CURVED STIFFENED PANELCOUPON


0

0.1

0.2

0.3

0.4

0.5

0 100 200 300 400 500

Distance from impact location to sensor position　，mm

Arr

ival

tim

e o

f st

rain

resp

onse

s　，

ms

□ FBG sensor (Stiffener direction) ● Strain gauge (Stiffener direction) ○ Strain gauge (Orthogonal to stiffener)

● Predected impact position× Impact position□ Sensor position

Arrival Time vs. Distance from Impact Point(Impacted at Stiffener Flange)

Predicted Impact Point(Impacted at Stiffener Flange)

Prediction of Impact Point Using Dynamic FBG ResponsePrediction of Impact Point Using Dynamic FBG Response


Impact Damage Detection –Small-Diameter Optical Fiber

Impact Damage Detection – AE

Damage Detection－BOTDR

Damage Detection – Smart Patch

Damage Suppression －SMA

Low Cost RTM/Health Monitoring

Length： 3 mDiameter： 1.5 m

Overview of Demonstrator

Damage Detection and Suppression DemonstratorDamage Detection and Suppression Demonstrator


OUTSIDE VIEW INSIDE VIEW

EMBEDDED SMALL-DIAMETEROPTICAL FIBER SENSORS

Arrangement of SmallArrangement of Small--Diameter Optical Fibers Diameter Optical Fibers in Upper Panel for Impact Damage Detectionin Upper Panel for Impact Damage Detection

SKIN, STRINGER AND SKIN/STRINGER ：20 Optical Fibers including 6 FBG Sensors


Damage Detection and Suppression DemonstratorDamage Detection and Suppression DemonstratorUpper Panel with Embedded Small-Diameter Optical Fiber Sensors

Mid-panel with Embedded FBG SensorsSkin(CFRP)

Loading Fixture(Steel)

Support Fixture(Steel)

Frame(Al alloy)

Trimmable Optical Fiber Connectors

Installed

Mid-panel with Embedded FBG Sensors

4


Impact Damage Detection TestImpact Damage Detection Testin Damage Detection and Suppression Demonstratorin Damage Detection and Suppression Demonstrator

Actuators for Flexural Load

Impact Test Machine

Dead Weight for Gravity Compensation

Impact Response Measuring System

Fixed Reaction Wall


Impact Damage Detection SystemImpact Damage Detection System

VISUALIZATION(by Takeda Lab, Univ. Tokyo)

ANALYSIS/EVALUATION(by Kawasaki Heavy Industries, Ltd.)




(2)(2) Structural Integrity Diagnosis and Evaluation of Structural Integrity Diagnosis and Evaluation of Advanced Composite Structures (Advanced Composite Structures (ACSACS--SIDESIDE) ) Project,Project, METIMETI Advanced Material & ProcessingAdvanced Material & Processingforfor NextNext--Generation Aircraft Structure ProgramGeneration Aircraft Structure Program(FY2003(FY2003--2007)2007)

(3) Integrated High(3) Integrated High--Resolution Distributed Strain Resolution Distributed Strain Monitoring with Embedded Optical Fibers in Monitoring with Embedded Optical Fibers in Composite (FY2007Composite (FY2007--))


ACSACS--SIDE ProjectSIDE ProjectPZTPZT--FBG Hybrid Active Damage Sensing SystemFBG Hybrid Active Damage Sensing System

Fuji Heavy Industries Hitachi CableUniv. TokyoTohoku Univ., AIST

0

5

10

15

20

25

30

35

1548 1549 1550 1551 1552

W ave leng th [nm ]

Tra

nsm

issi

on [

%] Filter 1 Filter 2

+ strain-strain

Lamb wave detection up to 1 MHzLamb wave detection up to 1 MHzAWG (arrayed waveguide grating) filterAWG (arrayed waveguide grating) filter

SAWDSAWDTMTM (Subaru Active Wave Detection) System(Subaru Active Wave Detection) System

SPIE Paper 6932-1


Monitoring of Monitoring of DebondingDebonding at Critical Regions or Hot Spots at Critical Regions or Hot Spots of CFRP Skinof CFRP Skin--Stringer Stringer BondlinesBondlines

PZT FBG Artificial defect

(unit: mm)

15

5

500970

40

16.5 16.5

300

5

10

Skin

Hat-shape stringer

Skin & Stringer: CFRP quasi-isotropic laminates


-40

-20

0

20

40

0 20 40 60 80 100

-40

-20

0

20

40

0 20 40 60 80 100

L = 0mm

L = 5mm

Time (μs)

Vol

tage

(m

V)

-40

-20

0

20

40

0 20 40 60 80 100

L = 7mm

-40

-20

0

20

40

0 20 40 60 80 100

L = 12mm40

0

-40

40

0

-40

40

0

-40

40

0

-40

0 20 40 60 80 100

5000

300

150

L = 0mm

L = 5mm

L = 7mm

L = 12mm

Freq

uenc

y

(kH

z)

0 20 40 60 80 100

5000

300

1505000

300

1505000

300

150

Arrival of the first peak became slower after debonding passed through FBG

Detected Lamb Waves with Growing Detected Lamb Waves with Growing DebondingDebonding(Bonded FBG (A))

Time (μs)

L

(A), (B)

(A) Bonded(B) Embedded

5


: Standard wavelet coefficient ijx ijx : Compared wavelet coefficient

( )∑ −=ij

ijijd

xxN

DI 21

calculated from all the distribution of the wavelet coefficients

Damage Index Damage Index DIDImax

max max

0

2 2

0 0

( ) ( )

( ) ( )

t t

tt t t t

t t

f t g tc

f t g t

=

=

= =

= =

⋅=

∑

∑ ∑

f(t)： Standard wavelet coefficient at 300kHzg(t)： Compared wavelet coefficient at 300kHz

Correlation Coefficient Correlation Coefficient cc

5000

300

150

L = 0mm

0 20 40 60 80 100 Time (ms)

Freq

uenc

y (k

Hz)

5000

300

150

L = 0mm

Time (ms)

L = 7mm

0 20 40 60 80 100

Definition of Damage Index Definition of Damage Index DIDI and Correlation Coefficient and Correlation Coefficient cc


0.6

0.8

1.0

1.2

0 2 4 6 8 10 120 2 4 8 126

Cor

rela

tion

Coe

ffici

ent

1.2

1.0

0.8

0.610

Debonding Length (mm)14

0

20

40

60

80

100

120

140

160

180

0 2 4 6 8 10 12 14

Dam

age

Inde

x

160

Debonding Length (mm)0 2 4 8 10 126

14012010080604020

0

0

2

4

6

8

10

12

14

0 2 4 6 8 10 12 14

Dam

age

Inde

x

14

Debonding Length (mm)

0 2 4 8 10 126 14

12

10

8

6

4

2

00


0.6

0.8

1.0

1.2

0 2 4 6 8 10 12


0 2 4 8 126

Cor

rela

tion

Coe

ffici

ent

1.2

1.0

0.8

0.6100

L

(A), (B)

Bonded FBG(A)

Embedded FBG(B)

DamageIndex

CorrelationCoefficient

CorrelationCoefficient

DamageIndex

180

Damage Index Damage Index DIDI and Correlation Coefficient and Correlation Coefficient cc as Functions of as Functions of DebondingDebonding LengthLength

Results by embedded FBG (B) changes rapidly around L = 6mm, which indicates that the debonding passed above the FBG (B).


(1) Read the waveforms detected by the damage monitoring deviceSAWD Damage Diagnosis SoftwareSAWD Damage Diagnosis Software


(2) Calculate the damage area by the damage diagnosis softwareSAWD Damage Diagnosis SoftwareSAWD Damage Diagnosis Software


Design allowable

Residual cyclic number

(3) Predict the damage growth by the residual life prognosis softwareSAWD Damage Diagnosis SoftwareSAWD Damage Diagnosis Software


Verification by SubVerification by Sub--Structure TestsStructure Tests

Ａｍｐ.Device

PC

Removable

Installing & cabling withFBG sensors/PZT

The system set-up was simulated for practical use in inspection or maintenance field

On ground (ex. hangar) On board permanently

Connected to the device

Size: 4000 X 2000 X 400 mm

To removable connector

Removable connector

O.F. & PZT cables

6


Correlation Point ofPump Light and Probe Light

Feature of BOCDAHigh spatial resolution （5 cm in length: Normal Mode）

(2 mm in length: HR Mode)High speed sampling rate (10Hz)Multi-points strain sensing (random access)

The phases of the pump and the probe light waves change periodically, it make the correlation peak position on the fiber. At the correlation peak position, the pump and the probe light waves are synchronously frequency modulated and maintain the frequency difference.

Pump Light Prove Light

Freq

uenc

y

Optical Fiber

Strain

Distance

Inte

nsity

Probe Frequency

Strain

Distance

Inte

nsity

Probe Frequency

ACSACS--SIDE ProjectSIDE ProjectBOCDABOCDA HighHigh--Resolution Distributed Strain MeasurementResolution Distributed Strain Measurement

Mitsubishi Heavy Industries, University of Tokyo

SPIE Paper 6933-29

BOCDA Principle (Brillouin Optical Correlation Domain Analysis) developed by Professor Hotate

ΔνS＝CSε＋CTΔT


Powersupply

Controlunit

Optical unit1. Bolted joint distributed strain monitoring

2. On-board type BOCDA system development3. Flight load monitoring using BOCDA system

Detect damage by distributed strain

Missing Fastener

Optical Fiber

Sensor

(2) On-board BOCDA system development

Structure life assessment

(3) Flight load monitoring using BOCDA system

Optical fiber sensor

BOCDABOCDA--SHM System DevelopmentSHM System Development

(1) Bolted portion monitoring

Monitor

Power Supply

Optical unit

Control unit

Monitor

Power Supply

Optical unit

Control unit

0

100

200

300

400

500

600

700

0 10 20 30 40 50 60 70 80 90

Time [sec]

Str

ain

[ue]

strain form BGS

Strain Gage


BOCDA Distributed Strain Measurement ResultsBOCDA Distributed Strain Measurement Results

– It was observed the clear deference in distributed strain between the intact structure and that with a missing bolt.

⇒structure defects (missing bolt) was detectable by high spatial resolution BOCDA system.

-500

0

500

1000

1500

2000

10.7 11 11.3 11.6

Position [m]

Stra

in [με]

Intact#5 bolt removed

#5 bolt

X=11.0

X=11.3

Opticalfiber sensor

Strain gage


<Flight condition>Pull upAlt: 15,000ft

<Measuring Condition>Dynamic sampling (60pt/sec)

On-board BOCDA system was successfully operated during flight conditions to assess structural load history

<Flight condition>Landing

<Measuring Condition>Dynamic sampling (60pt/sec)

-300-200-100

0100200300400

0 20 40 60 80 100

Time [sec]

Stra

in [με]

Strain from BOCDA

Strain Gage

-300-200-100

0100200300400

20 40 60 80 100

Time [sec]

Stra

in [με]

Strain from BOCDAStrain gage

Dynamic Flight Load MonitoringDynamic Flight Load Monitoring





(3) Integrated High(3) Integrated High--Resolution Distributed Strain Resolution Distributed Strain Monitoring with Embedded Optical Fibers in Monitoring with Embedded Optical Fibers in Composite (FY2007Composite (FY2007--))


PPPPPP--BOTDABOTDA sensing systemsensing system

Neubrescope(Neubrex Co., Ltd)

Pre-pump Pulse Brillouin Optical Time Domain AnalysisDistributed strain measurement

Spatial resolution: 10 cm Sampling interval: 5 cmSensing range: > 1 km (whole length of optical fiber)

7


大規模構造物への適用 (VaRTM成形中)

供試体内埋め込み

Vacuum Bag

T-II

S-II

T-I

S-I

Ligh

t Sw

itch

OSA

Light Source

(Path Change)PPP-

BO

TDA

2.1m

Strain Measurement During Strain Measurement During VaRTMVaRTM (Vacuum(Vacuum--assisted Resin assisted Resin Transfer Molding)Transfer Molding) Process of CFRP Stiffened StructuresProcess of CFRP Stiffened Structures

PPP-BOTDA and FBG Strain Measurements in a Single Fiber

Small-diameter optical fiber with high refraction index difference was effective to reduce the optical loss due to embedment

Comparison of Strains by FBG and PPP-BOTDA Measurement

Fiber Embedment


大規模構造物への適用 (VaRTM成形中)

-1 0 1 2 3-300

-200

-100

0

100

200

300

Distance (m)

Stra

in (μ

ε)

Residual Thermal Strain Distribution

FBG

Embedded Region

Strain Measurement During Strain Measurement During VaRTMVaRTM (Vacuum(Vacuum--assisted Resin assisted Resin Transfer Molding)Transfer Molding) Process of CFRP Stiffened StructuresProcess of CFRP Stiffened Structures

PPP-BOTDA and FBG Strain Measurements in a Single Fiber

Comparison of Strains by FBG and PPP-BOTDA Measurement


Damage Detection in CFRP Sandwich StructuresDamage Detection in CFRP Sandwich Structures

S. Minakuchi, et al., Journal of Sandwich Structures and Materials, 9 (1), pp 9-33, 2007.

Optical fiber acts as nerve to detect residual facesheet dent

Key1. Non-uniform strain is induced in optical fiber

in damaged area2. Facesheet dent is relatively wide

A limited number of optical fibers are sufficient to monitor whole structure


Dent and Strain Distribution Dent and Strain Distribution –– Theory and ExperimentsTheory and Experiments

Facesheet: CFRP UT500/#135 (Toho Tenax Co.,Ltd., [(0,90)3])

Core : AL 3/16 5052-.001, Thickness : 20 mm(Showa Aircraft Industry Co.)

Adhesive films : AF-163-2K (3M Co.)

Displacement rate : 0.5 mm/minMaximum displacement : 0.5, 1 mm

Residual dent and strainwas well reproduced


Response Simulation of SpectrumResponse Simulation of Spectrum

Calculate strain distributionalong embedded fiber

Calculate spectrumdepending on

measurement point

Simulation procedureDamage right above

embedded optical fiber

How spectrum changes when damage is introduced?

Developed optical software

Width of spectrum depends on damage sizeSmart Composite System Laboratory The University of Tokyo

Damage Detection TestDamage Detection TestSchematic of specimen Experimental set-up

Quasi-static indentation loadings were applied to introduce

simulated low velocity impact damage

Five kinds of maximum displacement :1, 2, 3, 4, 6.5 mm

Response depending on damage size was investigatedResponse depending on damage size was investigated

Diameter 12.7 mm

Facesheet: T700S/2500, [0/90]3SCore: Al 1/4-5052-.001

8


ResultsResults -1 mm was applied-

Load-displacement curves

Top view of center of specimen

2D-plot of F-1dB

I II III IVV

VI

VII

VIII III

IIIIV V

VIVII

VIII

Residual dent depth0.3 mm

(Invisible)

One line nearest to loading pointresponded to invisible damage


ResultsResults -2 mm was applied-Load-displacement curves


Number of responding linesand values of F-1dB increased,

as damage became large


I II III IV

III

IIIIV

2D-plot of F-1dB

V

VI

VII

VIII

VVI

VIIVIII


ResultsResults -3 mm was applied-Load-displacement curves


Responses of VI and VII differed,confirming high resolution

of the proposed system


I II III IV

III

IIIIV

2D-plot of F-1dB

V

VI

VII

VIII

VVI

VIIVIII


ResultsResults -6.5 mm was applied-

I II III IV

Load-displacement curves

Residual dent depth2.5 mm(Visible)

Occurrence of impactcan be detected

with high sensitivity


I II III IV

III

IIIIV

2D-plot of F-1dB

V

VI

VII

VIII

VVI

VIIVIII


Application of SHM Technology to NearApplication of SHM Technology to Near--Future Future

Affordable Composite Aircraft and Affordable Composite Aircraft and SpacesraftSpacesraft

(1)(1) Structural Health Monitoring Group,Structural Health Monitoring Group, NEDO Smart NEDO Smart Material/Structure System Program (FY1998Material/Structure System Program (FY1998--2002)2002)


(3) Integrated High(3) Integrated High--Resolution Distributed Strain Resolution Distributed Strain Monitoring with Embedded Optical Fibers in Monitoring with Embedded Optical Fibers in CompositeComposite StructuresStructures (FY2007(FY2007--))


SHM Aerospace Industrial Steering Committee (SHMSHM Aerospace Industrial Steering Committee (SHM--AISC) AISC) SAE GSAE G--11 Committee11 Committee

• Manufacturers:– Boeing– Airbus– EADS– Embraer– Bombardier– Lochkeed Martin– FHI

• System Integrators:– BAE– Honeywell– Goodrich– GE

• Regulatory Agencies:– FAA– EASA– US AF– US Army

• Research Organizations:– Stanford University– Sandia National Lab– Air Force Research of Scientific Research– University of Tokyo– University of Sheffield– NASA– NRC Canada– RIMCOF

• Operators/Users:– ATA

Documents

Boeing 787 Composite Structures - BRIDGE ... by Boeing Smart Composite System Laboratory The Universit y of Tok o Feb. 2005, Newton Composite Materials and Structures are most important