KEY NOTE TALK 2: NON-DESTRUCTIVE TESTING FOR COMPOSITE MATERIALS FROM LABORATORY FEASIBILITY STUDIES TO INDUSTRIAL PROOFED SOLUTIONS

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Carmella Griffith
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1 KEY NOTE TALK 2: NON-DESTRUCTIVE TESTING FOR COMPOSITE MATERIALS FROM LABORATORY FEASIBILITY STUDIES TO INDUSTRIAL PROOFED SOLUTIONS

The name giver: Joseph von Fraunhofer (1787 1826) Deutsches

spectrum Inventor New methods for processing lenses Entrepreneur

2 The name giver: Joseph von Fraunhofer ( ) Deutsches Museum Researcher Discovery of the Fraunhofer lines in the solar spectrum Inventor New methods for processing lenses Entrepreneur Director and partner in a glassworks -Gesellschaft»Fraunhofer-Lines«

3 NON-DESTRUCTIVE TESTING FOR COMPOSITE MATERIALS FROM LABORATORY FEASIBILITY STUDIES TO INDUSTRIAL PROOFED SOLUTIONS Fraunhofer IKTS, Dresden, Germany

4 NDT Matrix for CFRP inspection in automotive industry Source:

5 Inspection Tasks along the CFRP process chain Eddy Current Ultrasonic

6 High Frequency Eddy Current Technology

7 Using Complex Electrical Properties for CFRP Testing Electrical Effects at CFRPs 1. Fiber / Volume Ratio 2. Density 3. Capacitiv e Coupling Ref.: Zur Wirbelstromprüfung von kohlefaserverstärkten Kunststoffen, Dipl.-Ing. Rolf Lange, Magdeburg 1997 Conductivity Graphite: σ = S/m Aluminum: σ = S/m Carbon Fibre σ = to S/m (0 to Fibre) σ = 10 to 100 S/m (90 to Fibre) Average conductivity CFRP ca. 1/1000 of Aluminum Dielectrically Constant 1.8 to 2.5

8 Measurement Routines Complex Impedance Measurement Electrical Impedance of pick up Coil Imaging by Scanning Conductivity Textural Information Imaginary Part Phase Rotation Dielectricity Resin/Polymer Information (Dry Spots) Real Part Sample size 20 x 20 cm, 25µm 2 pixel

9 The EddyCus inspection technique Metal and Alloys testing Weak conductive materials e.g. security applications Thermography Penetration Depth Signal Amplitude 2 U Ind d dt

10 Contrast Mechanism Conductivity Detecting non conductive insertions Prepreg separation foil Paper PTFE Tape Copper mesh 1 2 3

11 EddyCus Textural Imaging of large CFRP Structure (1400 mm x 270 mm x 5 mm)

12 Photo Cross Section Left Side HFEC Image from top Photo Cross Section Right Side

13 Photo Cross Section Left Side HFEC Image from top Photo Cross Section Right Side

14 Textural Analyses by Image Frequency Analyses 2D Fast Fourier Transformation

0 Textural Analyses by 2D FFT for angle orientation and gap

15 Textural Analyses based on Image Processing Layer CAD Eddy Current Image 2D FFT Textural Analyses by 2D FFT for angle orientation and gap size analysis 7 Layer penetration, misalignment of 5 th layer by 2 was founded

16 Automated Image Interpretation by Inspection Software

17 Eddy Current on Non-Conductive Materials A permittivity change of coils neighborhood is influencing the coils Impedance Photograph Eddy Current Scan WS C-Scan POM (Polyoxymethylen) with air filled holes (Ø 5 mm)

20 Step-back towards Maxwell Equations Show Potential of HFEC for Permittivity Measurements of Dielectric Materials Maxwell equations*. leading to the following main conclusions A time varying magnetic field creates a rotating electric field E independent of the conductivity of the sample Both, eddy currents and displacement currents are influencing the coil s magnetic field and therefor coil impedance. Different phasing of conductivity vs. permittivity influences leading to unequal effect on coil impedance. * version for constant frequencies -10-

Monitoring of the Curing Process of Resin L20 @ Room Temperature Capacitive Reference Measurement (Destructive, Laboratory use) LCR meter HP4275A Comb electrode IDEX Model 065S A/D Ratio 80 Build

calibration) Im(Z)_norm [in %] Capacitance [in pf] 120 Capacitance 2MHz 4MHz 110 Dissipation Factor 2MHz 4MHz 100 90 80 70 60 50 40 0,02 0:00 1:12 2:24 3:36 4:48 6:00 Time since mixing [in

21 Monitoring of the Curing Process of Resin Room Temperature Capacitive Reference Measurement (Destructive, Laboratory use) LCR meter HP4275A Comb electrode IDEX Model 065S A/D Ratio 80 Build within Faraday cage HF EC Based Cure Monitor (non destructive, Industrial use) EddyCus CF map 4040 with T05 1-point measurement with 1 mm lift-off and separate reference point (stand-by and calibration) Im(Z)_norm [in %] Capacitance [in pf] 120 Capacitance 2MHz 4MHz 110 Dissipation Factor 2MHz 4MHz ,02 0:00 1:12 2:24 3:36 4:48 6:00 Time since mixing [in hours:minutes] 120 Im(Z)_norm 6MHz 2MHz 110 tan δ 6MHz 2MHz ,16 0,14 0,12 0,1 0,08 0,06 0, :00 01:12 02:24 03:36 04:48 06:00 Time since mixing [in hours:minutes] Dissipation Factor 0,16 0,14 0,12 0,1 0,08 0,06 0,04 0,02 tan δ

CFRP sample (top view), 10 x 10 cm Damaged induced by local overheating during

22 Permittivity Mapping to Identify Local Curing Defects in CFRP (Hot Spots) Defect not visible at photography but clearly visible at eddy current scan CFRP sample (top view), 10 x 10 cm Damaged induced by local overheating during cure EC 5 MHz with EddyCus CF map and Sensor T05 Induced damage visible, here red

Permittivity Mapping to Identify Local Curing Defects in CFRP (Hot Spots) Edge effects Changes of CFRP thickness, (which is a change in conductivity) can be clearly differentiated from the induced

23 Permittivity Mapping to Identify Local Curing Defects in CFRP (Hot Spots) Edge effects Changes of CFRP thickness, (which is a change in conductivity) can be clearly differentiated from the induced damages (permittivity change) analyzing the complex signal CFRP sample Hot spot surroundings Hot spot Edge effects and Lift-offs are more difficult to separate from permittivity changes as both represent a shift of the complex signal on the same axis

24 Infusion monitoring CFRP Optical camera (photo) 10MHz (before the resonance) Sensor position from bottom side 13MHz (after the resonance) Epoxy has not reached the sensor Epoxy has reached the sensor Curing process is in a progress EddyWet 2.0 CFRP

Epoxy has not reached the sensor Epoxy has reached

25 Infusion monitoring GFRP Optical camera (photo) 10MHz (before the resonance) 13MHz (after the resonance) Epoxy has not reached the sensor Epoxy has reached the sensor Curing process is in a progress EddyWet 2.0 GFRP

26 Industrialization of High Frequency Eddy Current Technology for Com pos ite Ins pection

Indus trialization of Academ ic Dev elopm ents The

& Feasibility: Principle Idea how something can be

be operated by PhD Students 7y Fab: Monolithic Device for

27 Indus trialization of Academ ic Dev elopm ents The Transition from Lab to Fab needs Know How an 10 Year Idea & Feasibility: Principle Idea how something can be measured / tested 3y Lab: Modular Laboratory Equipment to be operated by PhD Students 7y Fab: Monolithic Device for reliable staff operation EddyCus Impedance Spectrometer EddyCus Scanner

28 Industrialization of High Frequency Eddy Current Technology for Com pos ite Ins pection Single Spot Systems Rotating Single Spot Systems X-Y Scanners (2d) X-Y-Z Scanners (3d) Array Probe Technology

29 X-Y HIGH FREQUENCY EDDY CURRENT SCANNER (2008)

30 X-Y High Frequency Eddy Current Scanner (2010)

31 X-Y-Z HIGH FREQUENCY EDDY CURRENT SCANNER (2012) w w.y outube.com/w atch?v =w Nng6ClM1CM

32 EDDYCUS PREFORM INSPECTION SYSTEM AT DLR IN STADE EvO-Robot at DLR-Stade for NDT of CFRP-Stringer

33 3d Drape Tester for Multilayed Material Parametrisation Measurement Data Processing 1. Draping Process 2. Digitalization ROI 3. Scan Path Planning G. Bardl et al. Comp. B. 2016

34 2. ROTATING SINGLE SPOT SENSORS FOR ANGLE RESOLVED EDDY-CURRENT POLAR MAPPING Anisotropic Sensors for orientation mapping

35 ROTATING SINGLE SPOT SENSORS FOR ANGLE RESOLVED EDDY-CURRENT POLAR MAPPING

36 ROTATING MAGNETIC FILED BY RECTANGULAR COIL ARRAY Current flow upon in four coils and distribution of the magnetic potential Electronically switching of sensors orientation M Naidjate, B Helifa, M Feliachi, IK Lefkaier, H Heuer, M Schulze,, A Smart Eddy Current Sensor Dedicated to the nondestructive Evaluation of Carbon Fibers Reinforced Polymers, Sensors 17 (9), 1996, Patent pending

Conclusion Non-destructive testing for composite materials From laboratory feasibility studies to industrial proofed solutions Eddy Current technology works on Insulators (Polymers), Semiconductors

37 Conclusion Non-destructive testing for composite materials From laboratory feasibility studies to industrial proofed solutions Eddy Current technology works on Insulators (Polymers), Semiconductors (SiC) and weak conductive materials (CFRP) Works on dry, wet and consolidated Material Characterization of dielectrical properties for infusion monitoring Robot based Scanners for 3d surface imaging, Meter, Acoustic Impedance spectroscopy for polymer reaction monitoring Crack in SiC Structure (pure matrix, 75 mm 2 )

Investigation of Eddy Current Nondestructive Testing for Carbon Fiber-Reinforced Plastic (CFRP) Based on Electromagnetic Field Analysis

Journal of Mechanics Engineering and Automation 8 (2018) 127-131 doi: 10.17265/2159-5275/2018.03.004 D DAVID PUBLISHING Investigation of Eddy Current Nondestructive Testing for Carbon Fiber-Reinforced