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Functional Fiber Reinforced Plastic and Nondestructive Evaluation for
Advanced Maintenance
Toshiyuki TakagiInstitute of Fluid Science, Tohoku UniversityELyTMaX UMI 3757 CNRS, Tohoku University
Hiroyuki Kosukegawa and Tetsuya UchimotoInstitute of Fluid Science, Tohoku University
October 4, 2017 Tsukuba, JAPAN
International Joint Symposium of 3rd Innovative Measurement and Analysis for Structural Materials and TIA‐Fraunhofer Workshop
MATEIS, LAMCOSINSA-Lyon
IZFP, IKTSFraunhofer Institute
LTDSEcole Centrale de Lyon
Karlsruhe Inst. of Technology
Xi’an Jiaotong University
SIMAP,LEGIGrenoble INP
International research core on smart layered materials and structures for energy saving
Optimization of material design Material evaluation
AdvancedMaterials
Industrial application of smart layered structure
Sensing & control embedded in layered structures
Advanced heat transfer Kinetic energy control Energy saving
Sensing & Control
Flow Dynamics
EnergySaving
Saarland University
KTH, Sweden Royal Institute of Technology
Institute of Fluid ScienceTohoku University
Tohoku Univ.School of
Engineering
Tohoku Univ.NICHe Tohoku Univ.
FRIS
Kobe Univ. Tokai Univ.NIMS
The Univ. ofTokyo
Chiba Univ.
2
Nanjing University of Aeronautics and
Astronautics
Outline
1.Background 2.ECT for CFRP with HF, TR, D‐type Probe3.Numerical Simulation of ECT for CFRP4.ECT Application for Scarf Adhesive Repair5.Functionalization of CFRP6.Summary
4
Outline
1.Background 1.Maintenance activities2.CFRP and NDT
2.ECT for CFRP with HF, TR, D‐type Probe3.Numerical Simulation of ECT for CFRP4.ECT Application for Scarf Adhesive Repair5.Functionalization of CFRP6.Summary
5
The lifetime of artifacts
DesignFabrication
Operation
Decommission
6
Artifacts are made by human beings and for human beings
Inspection
MaintenanceInspection and repair
Large Scale Complex System
Maintenance Activities
MachineSystem
Do
Plan
Maintenance Cycle PDCAD
P
A
C
Action
Maintenance Activities
Maintenance Implementation
System
Human System
Check
7
‐Framework of Maintenance‐
Takayuki Aoki, Tohoku University
Design and Maintenance Supporting Safety Function
Maintenance
•Ins. Procedure•Inspector•Inspection
Equipment
•Accuracy (Detectability, Sizing)•Reliability (POD)
•Work Procedure•Worker•Special Tool etc.
Inspection Performance/Capability
Design
8
CorrectionInspection
Takayuki Aoki, Tohoku University
Optimization by Three Major Technologies of Maintenance
OptimizationVisualization
MonitoringInspection
PredictionEvaluation
Coping with consequences
Repair
CFRP in Various Industries10
Aerospace Civil Engineering Automobile
Tokyo Rope Mfg. Co., Ltd.
Nippon Graphite Fiber Co. BMW NEDO
JFECBoeing
JAXA
Toyota Motor Co.
Establishment of NDT/NDE technique is needed for quality assurance and reliability of CFRP structures
Environmental Engineering
Conventional NDT techniques are sometimes not suited for CFRP
CFRP in Various Industries11
Tokyo Rope MFG. Co., Ltd.
High pressure hydrogen vessel
Long CFRP wire
• Fatigue crack in metallic liner
• Delamination• Void
JFE Container Co., Ltd.
• Uncured resin• Fiber rupture
Lifecycle of CFRP12
Quality assurance and in‐service inspection of CFRP should be done at proper stages in its lifecycle
Partly referred from news release of NEDO (2013.9.3)
Defects in CFRP13
Delamination
http://www.appropedia.org/
Fiber rupture
NDT Techniques for CFRP14
P660(FLIR)
RIGAKU nano3DX X‐ray Microscope
EddyCus®, SURAGUS
Ultrasonic testing (UT) Thermographic Testing (TT)
Radiographic testing (RT) Eddy current testing (ET)
Applicability of NDT for CFRP
15
UT RT TT ECT
Delamination ◎ ○ ◎ ○
Other object ◎ ◎ ◎ ○
Void ◎ ◎ ○ ▲
Crack ◎ ◎ ○ ▲
Resin curing degree ▲ ▲ ○ ○
Water content △ ▲ ◎ ○
Fiber density ▲ ○ △ ○
Fiber orientation ▲ ○ ▲ ◎
Fiber rupture ▲ ○ ▲ ○
Misalignment ▲ ○ ▲ ◎
◎>○>△>▲
内田盛也 編, 先端複合材料の設計と加工(1988)より一部抜粋
Outline
1.Background2.ECT for CFRP with HF, TR, D‐type Probe3.Numerical Simulation of ECT for CFRP4.ECT Application for Scarf Adhesive Repair5.Functionalization of CFRP6.Summary
16
17Eddy Current Testing (ECT)Sensitive NDT method for conductive materialsInduction voltage of pickup coil
B: Magnetic flux density (Wb/m2)S: Area of pickup coil (m2)dS: Minute area of pickup coil (m2)
Eddy current skin depth
μ:Permeability (H/m)σ:Electric conductivity (S/m)
18
Electrical Conductivity of CFRPTransverse direction
Fiber direction
Thickness direction
Resin-rich Interlaminar
σL : 103 - 104 S/m
σT : 10 -102 S/m
σcp : 10-1 -10 S/m
Pratap, S.B., and Weldon, W.F., IEEE Transactions on Magnetics, 1996
Electrical conductivity of CFRP is 1/1000 to metalAn increase of EC signal is needed
19
How to Increase of EC signal
r''‐r': Vector from the point r' on eddy current region V' to the point r'' on pickup coil region
B: Magnetic flux density (T) A: Magnetic vector potential (H•A/m), μ:Permeability (H/m) σ:Electrical conductivity (S/m), S:Flat area on pickup coil vertical to B, dS: Tiny fragment of S L: Closed circle of S dl: Tiny fragment of Lr'‐r: Vector from the point r on exciting coil to the point r' on eddy current region V'Je: Eddy current density on objective (A/m)
• Frequency• Permeability• Conductivity
20
ECT for CFRP
Foreign body (UT and TT can do)Delamination (UT and TT can do)Fiber orientationFiber misalignmentUncured resin
ECT with HF and TR type probe at higher frequencies (> 3 MHz), whereas differential type probe requires relatively lower frequencies (< 3 MHz)
HF absolute TR
ECT can detect the defects originated from fiber
Differential type (D‐type)
21
Fraunhofer Institute for Nondestructive Testing– IZFP
Description Value
Scan area
Max. scan speed 70mm/s
Sensor type Single sensor16 channel/line array
Frequency 10kHz ~ 100MHz
Min. resolution
Protocol RS-232/Ethernet
EddyCus CF map 4040 (SURAGAS)
Changeable sensor kit
Anisotropic typeLateral pitch– 3.5mmTurns– 20
Scaleable 16 sensor demonstrator line arrayLateral resolution‐‐ 875μmPlanar scan speed 0.5m2/min
Martin H.Schulze, Henning Heuer, Martin Ku¨ttner, Norbert Meyendorf “High‐resolution eddy current sensor system for quality assessment of carbon fiber materials” Microsyst Technol (2010)16: 791–797
ECT for CFRP with HF and TR Probe
22
(a) Optical image(b) ECT C‐scan image(c) 2D FFT spectrum
Martin H.Schulze, Henning Heuer, Martin Ku¨ttner, Norbert Meyendorf “High‐resolution eddy current sensor system for quality assessment of carbon fiber materials” Microsyst Technol (2010)16: 791–797
16 sensor in line arrayScan speed: 60 mm/sf = 2 MHz ~ 10MHz
(a) (b) (c)
Original After filtering with 2D‐FFT
Fiber orientationECT for CFRP with HF and TR Probe
23
Fiber Orientation by D‐type ProbeC‐scan image 2D FFT
spectrum
45deg ‐45deg0deg 90deg
Scan range : 20×20 mm2
Separation of fiber orientation by the inverse FFT
M, N: arbitrary natural numbersu, v: frequency component of the spatial wave in x‐ and y‐direction
Urayama, R., Takagi, T., et al., Studies in Appl Electromag Mech, 41 (2016) 18‐25
2 MHz
Outline
1.Background 2.ECT for CFRP with HF, TR, D‐type Probe3.Numerical Simulation of ECT for CFRP4.ECT Application for Scarf Adhesive Repair5.Functionalization of CFRP6.Summary
24
25
Numerical Simulation of ECT for CFRP
By distinguishing the calculation regions into current source (exciting coil) and pickup coil and objectives (CFRP),edge elements are used
in Vt
in Vt + Vtr
in Str
Biot-Savart's law
Reduced Magnetic Vector Potential method (Ar method)
Governing equations
Boundary conditions
26
Numerical Simulation of ECT for CFRP
Cheng, H., Takagi, T., et al. NDT&E, vol.68 (2014) pp.1‐12
Eddy current density, Jx (A/m2)
UD-ply Cross-ply QI laminates
ECT signal analysis of fiber orientation by FEM250 kHz
27
Numerical Simulation of ECT for CFRP
X
Y
θ′
Coils
UD Cross
Normalized ECT signal according to the angle between fiber orientation and TR axis
Cheng, H., Takagi, T., et al. NDT&E, vol.68 (2014) pp.1‐12
250 kHz
QI laminate
ECT signal analysis of fiber orientation by FEM
28
FEM for Fiber OrientationFinite element analysis of eddy current distribution was carried out to discuss the results of ECT of UD‐LP laminates.
PHOTO‐Series EDDY jω (Photon Co., Ltd.)Isoparametric elementsA‐method
XZ
Y CFRP
Full model dimension: 100 × 100 × 2.4 (mm)Mesh number of elements: 530,000
Direction σx σy σz
0 degree 14860 3.8 0.63
90 degree (LP) 3.8 14860 0.63
Electrical conductivity of CFRP[Cheng, J., Takagi T., Composite Mater, 2015]
Frequency 2 MHz
O.D. 4.5 mm
I.D. 4.0 mm
Current 1.85 A
Number of turn 185
Height 2.3 mm
0.24mm
90º
0º
LP1 LP2
29
1st[90]/2nd[0]1st[90]
1600
0J (A/m
2 )
10 mm
2nd[0]/3rd[0]LP1
LP2 1600
0
J (A/m
2 )1st[0]/2nd[90]1st[0] 2nd[90]/3rd[0]
EC density shows large value at the interface of the layers with different orientation
EC signal from subsurface is larger than from the surface
FEM for Fiber Orientation
30
LP1 LP3LP2 LP5
Highest value at subsurface layer
Detectability of Fiber Orientation
Sample varianceDefinition of detectability
V : Sample variancen : Number of measured points
X: Amplitude at the measured point : Overall average of the amplitude
Outline
1.Background 2.ECT for CFRP with HF, TR, D‐type Probe3.Numerical Simulation of ECT for CFRP4.ECT Application for Scarf Adhesive Repair5.Functionalization of CFRP6.Summary
31
32
Siemens
Lightning
Dexmet Corporation, “Lightning Strike Protection for Carbon Fiber Aircraft” JAPAN AIRLINES資料
Bird strike
Cause of Failure
Repair of FRP Aircraft33
Scarf Adhesive RepairMethod of reconstructing structural function up to nearly 100%‐ Sanding the surface of FRP in scarfed shape by setting the defect at the center‐ Adhering adhesive film and prepreg patches according to peripheral lamination geometry
Boeing, http://www.compositesworld.com/articles/composites‐repair
The above procedures are performed by hand
Procedure of Scarf Repair① Detection of defect by NDT
② Grinding to the depth of the defect
③ Grinding in tapered shape (30:1 = radius : depth)
④ Shape extraction and cutting of prepreg patches
⑤ Patching adhesive film and prepreg patches
⑥ Curing → NDI by UT → (GOOD) → Polishing→ (BAD) → Return to ①
‐ Requirement of advanced technique‐ Depression of cost and service time‐ Inhibition of popularization of CFRP aircraft
35
Automation of scarf repair is needed for improvement the performance of FRP
Identification of Scarfed Laminates
• Fiber orientation• Geometry of each prepreg (boundary of adjacent layers)
Shape extraction of prepreg patches
36
Material ‐ Scarfed CFRP
[(452/02/‐452/902)3]S
Autoclave method Prepreg compression method[‐457/907/‐457]
‐ Fiber Orientation ‐ Boundary
[907/457/907][07/457/07] [07/‐457/07]
120 min, 130ºC, 0.5 MPa120 min, 130ºC, 0.5 MPa
P3252S‐25 (Toray, t = 0.24 mm)TR380G250S (Mitsubishi Rayon Co., Ltd.), t = 0.24 mm)
220 x 110 x 11 (mm3) 150 x 75 x 5 (mm3)
37
ECT Setup
Frequency: 10 MHz (fiber orientation), 2 MHz (boundary)Exciting voltage: 5.0 Vp‐p(fiber orientation), 3.0Vp‐p (boundary)Gain: 10~20dB
38
Identification of Scarfed Laminates
Scan pitch: 0.1 mmFrequency: 10 MHzVoltage: 5.0 Vp‐pGain: 10~20dB
39
FEM for EC on Scarfed Surface
Number of elements: 345,600Frequency: 10 MHzExciting current: 5.7 x 10‐2 A x 27 T (same as the experiment)
EC distribution on the scarfed surface and interface of [‐45/90]
σL (S/m) 14860
σT (S/m) 3.8
σcp (S/m) 0.63
40
FEM for EC on Scarfed Surface
EC signal from the interface of 1st and 2nd layers is strong
41
Necessary to extract the signal from the surface layer
Identification of Scarfed Laminates
Fiber orientation of surface layer
Boundary
Fiber orientation of second layer
42
EC signal contour
30 32 34 36 38 40 42 44
2D‐FFT Spectrum
k
30 32 34 36 38 40 42 44
By filtering with 2D‐FFT, fiber orientation on the scarfed surface can be extracted
Extraction of Fiber Orientation
l
43
Respective layer is identified with 2D‐FFT filtering
45º ‐45º90º 0º
0 15X (mm) X (mm) X (mm) X (mm)
0
15
15 30 30 45 45 600
15
0
15
0
15
y(m
m)
y(m
m)
y(m
m)
y(m
m)
Extraction of Fiber Orientation
44
Identification of Boundary
45º/90º boundary
True boundary ( = 15.4 mm) True boundary ( = 29.2 mm)Peak position ( = 17.7 mm) Peak position ( = 30.5 mm)
Difference:2.3 mm
The peaks are shifted from the true boundaries
90º/-45º boundary
Difference:1.3 mm
Outline
1.Background 2.ECT for CFRP with HF, TR, D‐type Probe3.Numerical Simulation of ECT for CFRP4.ECT Application for Scarf Adhesive Repair5.Functionalization of CFRP6.Summary
45
46
Nanoparticle Dispersed CFRPDispersion of nanoparticles in matrix increases mechanical properties of FRP
*T. Takayama, H. Kosukegawa, T. Takagi, Proceedings of AFI2016, (2016) 20‐21
Because Ep‐f becomes higher than Ep‐p, EcT increases by distributing nanoparticles in matrix
m, p, f mean matrix, particle and fiberE [Pa]: elastic modulus d [m]: diameter
V [-]: volume fraction of filler Lf [m]: fiber lengthL [m] and a [m] : interfiller distance between particle and fiber
47
Manufacturing1. Dispersion of nanoparticles into
epoxy resin is performed with a rotation‐revolution mixer
100ºC, 2h
VacuumingEpoxy/nanoparticle
solution
Pressure
Vacuum bagDispersing mediaFiber fabric
Aluminum tool
Epoxy/NPSolution
Revolution
RotationSchematic of dispersing
NP: nanoparticle
2. The solution is introduced into the fabric by vacuum‐assisted resin transfer molding (VaRTM) method
48
Nanoparticle Dispersed FRP
*T. Takayama, H. Kosukegawa, T. Takagi, Proceedings of AFI2016, (2016) 20‐21
T250 : D50 = 250 nm T90 : D50 = 90 nm
Cross section of nanosizedTiO2 particles dispersed CFRP
Theory considering the effect of interparticle and interfiller distance can explain the improvement of mechanical properties
TiO2: 4wt% in resin
49
Nanoparticle Dispersed FRP
Frequency: 200 kHz
×20
UD‐ply CFRP
Acrylic plate
Ferromagnetic nanoparticles dispersed CFRP (Mag‐CFRP)
Magnetic characteristics of CFRP drastically increase of EC signal
50
Nanoparticle Dispersed FRP
K: Constant depending on exciting coilC, D: Constant i: Indicatorα: Integral variation r: Coil position
C. V. Dodd, W. E. Deeds, Journal of Applied Physics, 39‐6 (1968) pp. 2829‐2838
Amplification of EC signal of is well expressed by the analytical solution
Ferromagnetic nanoparticles dispersed CFRP (Mag‐CFRP)Fe2O3: 5wt%
51
Nanoparticle Dispersed FRP
Rupture: L = 50 mm
Rupture at 2nd layer 0wt% 5wt%
Differential type probe 200 kHz
ECT can detect the fiber rupture of Mag‐CFRP even though no NDTs cannot detect.
Ferromagnetic nanoparticles dispersed CFRP (Mag‐CFRP)
Outline
1.Background 2.ECT for CFRP with HF, TR, D‐type Probe3.Numerical Simulation of ECT for CFRP4.ECT Application for Scarf Adhesive Repair5.Functionalization of CFRP6.Summary
52
53
Summary1. Electromagnetic NDT techniques of CFRP structures for
quality assurance and in‐service inspections are now under development.
2. NDT methods for automatic repair techniques are necessary for advanced maintenance.
3. Functional CFRP with ferromagnetic nanoparticles drastically increases the detectability of defect (even fiber rupture) by ECT.
4. NDT planning and inspection based on numerical modeling combined with IoT and big data will be beneficial for better maintenance activities.
AcknowledgmentsThis study was supported by a JSPS Core‐to‐Core Program, A. Advanced Research Networks, “International research core on smart layered materials and structures for energy saving”.
Thank you very much for your kind attention !