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!