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Non-Destructive Impact Damage
Detection on Carbon Fiber
Reinforced Plastics
BRAGECRIM 9th Annual Meeting
Speaker: Sarah Ekanayake M.Sc.
Prof. Dr.-Ing. Robert Schmitt
WZL of RWTH Aachen University
Prof. Dr. Eng. Armando Albertazzi Gonçalves Jr.
LABMETRO / EMC / UFSC
November 08th - 10th 2017 Salvador, Brazil
Slide 2
Project Consortium
German and Brazilian Project Partners
RWTH Aachen University
Laboratory for Machine Tools and
Production Engineering (WZL)
– Prof. Dr.-Ing. Robert Schmitt
– Sarah Ekanayake (Research Associate)
UFSC Federal University of Santa Catarina
(Florianópolis BR)
LABMETRO Laboratory of Metrology and Automation
– Prof. Dr. Eng. Armando Albertazzi Gonçalves Jr.
– Bernardo Cassimiro Fonseca de Oliveira (PhD
Student)
– Artur Antonio Seibert (PhD Student)
UFABC Federal University of ABC (Santo André BR)
CECS Engineering, Modelling, Applied Social Sciences
Centre
Prof. Dr. Eng. Crhistian Raffaelo Baldo
Slide 3
Summary & Outlook5
Experimental Investigations and Results4
Method for CFRP defects' depth determination3
Project Proposal2
Project Consortium1
Agenda
Slide 4
Project Proposal
IDD-Metro Project
Component Analysis
. materials
. geometries
. impact damages
Sample Preparation
. structuring
. experiments
. design of experiments
(DoE)
Thermography
. parameters optimization
. images dimensioning
. tests and validation
Computed Tomography
. parameters definition
. optimal volumetric matrix
. tests and validation
Defects Attributes
. identification
. structuring
. data model
Defects Modelling
Data Fusion
Multisensor Solution
. 3D digitalization
. thermography
. data fusion
. validation
2nd Phase (2018-2019)
1st Phase (2015-2017)
Slide 5
Motivation
Metrology as Enabler for Mass Production
Requirements: Sufficient process capability, low unit costs, high
volume production & efficient maintenance/repair process
Repair process
– High reproducibility, high process variation
– Accurate repair process to reduce oversizing
– Workshop capable and easy to handle systems
Demand for metrology performance
– Reliable testing processes for CFRP damages
– Worker independent defect evaluation
– Robust
– Time and cost efficient
Solution: Automated defect detection & quality assurance
Courtesy of:: Repower Systems AG
Courtesy of: Airbus S.A.S
Courtesy of: BMW AG
Slide 6
Summary & Outlook5
Experimental Investigations and Results4
Method for CFRP defects' depth determination3
Project Proposal2
Project Consortium1
Agenda
Slide 7
Method
Active Lock-in Thermography
Computer
Part illumination with sinusoidal
excitation frequency 𝑓 using
halogen spot lights
Change of heat transfer due to
inhomogeneities (e.g. defects)
Recording of IR radiation on the
part surface with IR camera
Data processing and information
representation as phase image
(Fourier transformation)
Phase information assigned to
defect´s depth position 𝑑
Defect
IR-Camera
Slide 8
Method
Challenges for Depth Determination
1. Thermal properties α are
material dependent
Current measurement processes are not applicable to real defects
2. The thermal contact resistance
Ω influences the reflection
coefficient
Thermal diffusivity
Reflection coefficient
Phase v
alu
e
3. Lateral heat flow falsifies the
measured phase value 𝜑 in
dependence on the excitation
frequency 𝑓
Slide 9
Method
Calculation of Defects´ Depth
Depth not directly
measurable with
thermography
Measurement problem with
five unknown parameters 𝛼,𝑓, φ, Ω𝑒, 𝑑
Numerical modeling of
solution space for every
possible variable
combination
Development of solution
approach for determination
of five unknown
Reduction of solution space
due to determination of
unknown parameters
Theoretical modeling
• Measurement of thermal diffusivity 𝛼𝛼
• Determination of the optimized excitation frequency 𝑓𝑜𝑝𝑡 and phase value φ𝑜𝑝𝑡
𝑓𝑜𝑝𝑡φ𝑜𝑝𝑡
• Determination of the contact resistance dependent on the contact resistance and the materials effusivity Ω𝑒
Ω𝑒
• Determination of defects depth position𝑑
Slide 10
Method
Determination of Thermal Diffusivity 𝛼
𝛼
𝑓𝑜𝑝𝑡φ𝑜𝑝𝑡
Ω𝑒
𝑑
Specimen
Halogen spot lights
IR-Camera
Assumption:
Real reflection coefficient 𝑅23
Thickness measurement at calibrated depth 𝑑𝑘𝑎𝑙
Procedure:
Known parameters from measurement: 𝑓,φ,
Extracted data from the theoretical model for the
given parameters 𝑅23, 𝑑𝑘𝑎𝑙 , 𝑓, 𝜑
𝑑 = 𝑓 𝛼, 𝑓, 𝜑, 𝑅23 ⇒ 𝛼 = 𝑔 𝑅23, 𝑑𝑘𝑎𝑙 , 𝑓, 𝜑
Results:
Determination of thermal diffusivity 𝛼
Slide 11
Method
Determination of Optimal Excitation Frequency 𝒇𝒐𝒑𝒕Goal
Minimization of lateral heat flow
Procedure
Thermography measurement from high to low
excitation frequencies 𝑓
Identification of optimized excitation frequency 𝑓𝑜𝑝𝑡
– As high as possible
– Differentiable from φ = −45°
Correlation of frequency and thermal
depth penetration:
𝜇 =α
π∗𝑓
𝛼 thermal diffusivity
𝑓 excitation frequency
𝜇 thermal depth penetration
Source: Spießberger, 2012
𝛼
𝑓𝑜𝑝𝑡φ𝑜𝑝𝑡
Ω𝑒
𝑑
Slide 12
Method
Determination of Ω𝒆 and defect´s depth 𝑑
Row
index
𝒊𝒛
Depth
𝑑
Factor
𝜴𝒆
Phase value
for 𝒇𝟏
… Phase value
for 𝒇𝒎
1 𝑑1 𝛺𝑒1 𝜑(𝑑1, 𝛺𝑒1, 𝑓1) … 𝜑(𝑑1, 𝛺𝑒1, 𝑓𝑚)
… … 𝛺𝑒1 … … …
𝑗 𝑑𝑗 𝛺𝑒1 𝜑(𝑑𝑗 , 𝛺𝑒1, 𝑓1) … 𝜑(𝑑𝑗 , 𝛺𝑒1, 𝑓𝑚)
𝑗 + 1 𝑑1 𝛺𝑒2 𝜑(𝑑1, 𝛺𝑒2, 𝑓1) … 𝜑(𝑑1, 𝛺𝑒2, 𝑓𝑚)
… … 𝛺𝑒2 … … …
2𝑗 𝑑𝑗 𝛺𝑒2 𝜑(𝑑𝑗 , 𝛺𝑒2, 𝑓1) … 𝜑(𝑑𝑗 , 𝛺𝑒2, 𝑓𝑚)
… … … … … …
(𝑘 𝑑1 𝛺𝑒𝑘 𝜑(𝑑1, 𝛺𝑒𝑘, 𝑓1) … 𝜑(𝑑1, 𝛺𝑒𝑘, 𝑓𝑚)
… … 𝛺𝑒𝑘 … … …
𝑘 𝑗 𝑑𝑗 𝛺𝑒𝑘 𝜑(𝑑𝑗 , 𝛺𝑒𝑘, 𝑓1) … 𝜑(𝑑𝑗 , 𝛺𝑒𝑘, 𝑓𝑚)
Complex wave field for given excitation frequency and
thermal diffusivity (𝒇 = 𝟎, 𝟎𝟐 𝑯𝒛 and𝜶 = 𝟒 ∙ 𝟏𝟎− 𝟕𝒎𝟐/𝒔)
Look-up-Table for 𝛀𝒆 and defect´s depth 𝒅
𝛼
𝑓𝑜𝑝𝑡φ𝑜𝑝𝑡
Ω𝑒
𝑑Source: Spießberger, 2012
Slide 13
Summary & Outlook5
Experimental Investigations and Results4
Method for CFRP defects' depth determination3
Project Proposal2
Project Consortium1
Agenda
Slide 14
Experimental Investigation
Specimen Preparation & Calibration Measurement
Test samples
– CFRP plates with multidirectional fiber
orientation (0°, 45°,90°)
– Blind bore holes with variable remaining wall
thickness & hole diameter
– Wedge with continuous thickness progression
Calibration measurement with the CMM
– System Zeiss Micura
– Calibration of blind bore hole center
– Measurement of remaining wall thickness
– Determination of wedge thickness at six points
Source: zeiss.deall values in [mm]
Slide 15
Experimental Investigation
Thermography Measurement with decreasing 𝑓
𝒇 = 𝟎, 𝟎𝟐 𝑯𝒛 𝒇 = 𝟎, 𝟎𝟏 𝑯𝒛
Slide 16
Deviation [%] of current state of the art measurement procedure
Devia
tion [
%]
Bore hole diameter [mm]
Remaining wall thickness [mm]
Experimental Investigation
Comparison of Thermography and CMM Measurement
Deviation [%] of developed measurement procedure
De
via
tion [
%]
Remaining wall thickness [mm]
Bore hole diameter [mm]
Source: Spießberger, 2012
Slide 17
Upcoming Experimental Investigation
Depth Determination with Contact Resistance Ω
Sketch: Water jet cutted plate Phase image Picture: Water jet cutted CFRP-plate
Double-sided
adhesive tape
Slide 18
Upcoming Experimental Investigation
Depth Determination on Impacted Specimens
Impacted specimen Phase image
d (Lock-in thermography)
d (Ultrasound)
Ωe (Lock-in thermography)
Slide 19
Summary & Outlook5
Experimental Investigations and Results4
Method for CFRP defects' depth determination3
Project Proposal2
Project Consortium1
Agenda
Slide 20
Summary & Outlook
Reliable Measurement Process for Depth Determination
Summary
Minimization of lateral heat flow during lock-
in thermography measurement &
improvement of the depth measurement
process
Proof of capability for water jet cutted
samples with contact resistance and impact
damaged samplesOutlook
Experimental investigations of samples with
contact resistance
Computed tomography measurement as
reference
Adjustment for complex CFRP-part
geometries
Slide 21
Thank you for your attention!