Porosity Characterisation in Carbon Composites ... - HS AalenAdvantages of Carbon Fibre Reinforced...

02.11.2011 1

Porosity Characterisation in Carbon Composites by

X-Ray Computed Tomography and

Image Analysis and Validation by

Materialografic Targeted Microsection

Sara Schuster

B. Eng. A. Ockert

Markus Reuber

Dipl. Ing. K. Pfeffer

Prof. Dr. S. Schuhmacher

Dr. M. Keigler

3D Microstructure Meeting Saarbrücken Sara Schuster

Supported by the State of

Baden-Württemberg within the

context of the project

"Innovative

Projekte/Kooperationsprojekte"

Advantages of Carbon Fibre Reinforced Plastics (CFRP)

● Very high mechanical strength

● 50 % weight reduction compared to steel, 30 % compared to Al

● High modulus of elasticity

● Resistance to corrosion

● Very good fatigue strength

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Present disadvantages

● High production costs

● Long production time


Development efforts in industry

● Reduce production costs

● Reduce production time

● Realize mass production

Developing the Resin Transfer Moulding (RTM) technology

Porosity formation is immanent in the manufacturing prozess

● Rule of thumb: 1% porosity decrease mechanicel strength 10%

3D Microstructure Meeting Saarbrücken Sara Schuster 02.11.2011 3

Reasons for research

● Porosity decreases mechanical strength

● Distribution, size and shape of pores influences strength

● Necessity is the evaluation of these pore parameters


Purpose of the research


Mikro-CT and 3-D-Image-Analysis is a tool for

Development of Non-Destructive

Testing (NDT) –Methods

-Ultrasound

-Thermography

Strength tests

X-ray computer tomography

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• Digital detector:

2000 x 1500 Pixel, Pixel size ca. 124 µm

• Detail perceptibility:

< 1 µm (Nano focus tube)

• Software used for analysis:

Volume Graphics VGStudio MAX 2.0

Parameter Micro focus Nano focus

Resolution 20 µm 10 µm

Current 240 kV 180 kV

Phoenix v|tome|x s

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02.11.2011

Samples Preparation

and Computed Tomography

Measurements

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3 4

C.F. Maier

within the context of

Bachelor thesis

of A. Ockert

Voxel size: 60 µm

Voxel size: 10 µm


● Problem 1- Verification and Validation of volume

porosity till now only by chemical analysis

No statement possible regarding the

size distribution, orientation and shape of

pores

● Problem 2 - Calibration

define threshold value


Targeted Microsection and Light Microscopy for

Verification and Calibration


Light microscope – image acquisition

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1 2 3 4 5 6 7 8 9 10 11 12

13 14 15 16 17 18 19 20 21 22 23 24

25 26 27 28 29 30 31 32 33 34 35 36

37 38 39 40 41 42 43 44 45 46 47 48

49 50 51 52 53 54 55 56 57 58 59 60

61 62 63 64 65 66 67 68 69 70 71 72

73 74 75 76 77 78 79 80 81 82 83 84

85 86 87 88 89 90 91 92 93 94 95 96

97 98 99 100 101 102 103 104 105 106 107 108

109 110 111 112 113 114 115 116 117 118 119 120

121 122 123 124 125 126 127 128 129 130 131 132

133 134 135 136 137 138 139 140 141 142 143 144

145 146 147 148 149 150 151 152 153 154 155 156

Mosaik-Image

• Take single images

• Overlap of images of 10 %

• Stitch images together

Creating one image with

50x magnification


Comparison of

CT-Slice and Microsection


Comparison of CT-Slice and Microsection

xz-plane

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Voxel size: 10 µm

CT-Slice Microsection

z

x

z

x


Magnification: 50x

Comparison of CT-Slice and Microsection

xy-plane


Microsection Magnification: 50x

CT-Slice Voxel size: 10 µm

x

y

x

y

Segmentation with interactive global threshold value

method

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Inte

nsity

Gray-scale values

Histogram

● graphic representation of grey-scale

values in one image

Segmented image Binary image

g: grey value

t: theshold value

Creating an output image with

segments 0 and 1 Analysis


02.11.2011 3D Microstructure Meeting Saarbrücken Sara Schuster

Calibration by

Comparision of segmented

CT-Slices with Microsection

(2D)

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Longitudinal microsection

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Microsection

Not segmented

Segmented

CT-Slice and

Microsection

Voxel size: 10 µm

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CT-Slice

Microsection CT-Slice

02.11.2011


Transverse microsection

● Wird Montag hinzugefügt



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Segmentation of Pores

and creating pairs

Comparison of

parameters and

calculating deviation

Evaluation - Comparison of pores parameters of

CT-Slices and Microsection

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CT-Slice Microsection P1

P2

P3

P4

Magnification of a rounded pore


CT-Slice

CT-Slice

Microsection

Microsection

Magnification of a elongated pore


CT-Slice

CT-Slice

Microsection

Microsection

Classification

Rounded shape

● based on the equivalent

diameter


Elongated shape

● based on feret min

Eq Diameter

Smal: 10-20 voxel size

Medium: 20-30 voxel size

Large: > 30 voxel size

Feret min

Smal: 10-15 voxel size

Medium: 15-20 voxel size

Large: >20 voxel size

Classification


Smal: 10-20x voxel size

Medium: 20-30x voxel size

Large: > 30x voxel size

Rounded shape

Elongated shape

Smal: 10-15x voxel size

Medium: 15-20x voxel size

Large: > 20x voxel size


Results of Estimation

for various types of samples

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Average deviation of elongated shape


36,5

13,0

6,8

32,0

9,4 8,6

19,1

13,7

2,9

38,3

14,2

8,6

34,3

20,0 18,8

Smal 10-15xVoxel size Medium 15-20xVoxel size Large >20xVoxel size

Area [%] Feret max [%] Feret min [%] f0 [%] f1 [%]

Evaluation > 10 x voxel size of Feret min

N = 20 pores each class

Average deviation of rounded shape


10,9

8,6

6,2 5,7

4,8

3,5

6,7

5,9

5,0

8,4

6,9

4,1

Smal 10-20xVoxelgröße Medium 20-30xVoxelgröße Large >30xVoxelgröße

Area [%] EqDiameter [%] f0 [%] f1 [%]

Evaluation > 10 x voxel size of EqDiameter

N = 20 pores each class

Future objectives


Dimensions: 15 mm x 15 mm x 4 mm

Voxel size: 10 µm

● Estimation of the:

● distribution of pores 2D/ 3D

● 3D-orientation


Many thanks for your attention!!!

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Dimensions: 15mmx15mmx8mm

Voxel size: 10 µm

CT-Slice

CT-Slice

15mmx15mm

Microsection

Microsection

Not segmented

Segmented

CT-Slice and

Microsection

z

z x

x


segmented

Not

segmented

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Dimensions: 15mmx15mmx8mm

Voxel size: 10 µm

CT-Slice

CT-Slice Microsection

Microsection

y

y

x


Segmented

CT-Slice and

Microsection

Not segmented

CT-Slice

CT-Slice

Microsection

Microsection

30 mm x 30 mm

Dimensions: 30 mm x 30 mm x 8 mm

Voxel size: 20 µm

x

x

z

z



Typical dimensions of pores in CFRP-samples

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CT-Slice CT-Slice

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Porosity Characterisation in Carbon Composites ... - HS AalenAdvantages of Carbon Fibre Reinforced...

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