Danksagung .................................................... III
Nomenclature .................................................... 8
Kurzfassung .................................................... 11
Abstract ....................................................... 13
1 Introduction ................................................ 15
2 Specification of investigated topic ......................... 17
3 State-of-the-art in CMC technologies ........................ 19
3.1 Processing and microstructure of C/C-SiC ............... 19
3.2 State-of-the-Art in mechanics of CMCs .................. 20
3.2.1 Differentiation between WIC and WMC materials ... 20
3.2.2 Bending and tensile strength ratio .............. 22
3.2.3 Interlaminar fracture mechanics ................. 23
3.3 Defects in CMC samples and structures .................. 24
3.4 Motivation ............................................. 25
4 Experimental Set-up ......................................... 27
4.1 NDI Set-up ............................................. 27
4.1.1 Ultrasonic testing .............................. 27
4.1.2 Micro-Computer Tomography ....................... 28
4.2 Mechanical testing ..................................... 28
4.2.1 In-plane testing: bending, tensile and SENB
testing ......................................... 29
4.2.2 Interlaminar mechanical testing ................. 31
4.2.2.1 Mode I interlaminar testing: DCB ....... 31
4.2.2.2 Mode II interlaminar testing: ENF ...... 33
5 Investigated material ....................................... 35
5.1 Processing of plate materials .......................... 35
5.2 Formation and definition of delaminations in C/C-SiC
plate material ......................................... 36
6 Mechanical behaviour of C/C-SiC without manufacturing
defects ..................................................... 39
6.1 Experimental results ................................... 39
6.1.1 Tensile and bending tests of siliconized and
desiliconized C/C-SiC in fibre direction ........ 39
6.1.2 Tensile and bending tests in varying
orientations .................................... 44
6.1.3 SENB testing .................................... 47
6.1.4 Interlaminar test results ....................... 49
6.1.4.1 Mode I: DCB ............................ 50
6.1.4.2 Mode II: ENF ........................... 58
6.2 FE-setup ............................................... 64
6.2.1 In-plane modelling: tensile, bending, SENB
test ............................................ 64
6.2.2 Modelling of interlaminar behaviour ............. 75
6.2.2.1 DCB-model .............................. 75
6.2.2.2 ENF-model .............................. 76
6.3 FE- and experimental results ........................... 77
6.3.1 Non-linear behaviour under tensile load ......... 77
6.3.2 Non-linear behaviour under bending load ......... 78
6.3.3 Bending and SENB failure ........................ 79
6.3.4 DCB-results ..................................... 86
6.3.5 ENF-results ..................................... 89
7 Mechanical behaviour of C/C-SiC with manufacturing
defects .................................................... 101
7.1 C/C-SiC with free Silicon ............................. 101
7.1.1 Results from NDT - sample taking ............... 101
7.1.2 Results from bending test ...................... 103
7.2 FE-modelling based on CT-data for C/C-SiC with
delaminations ......................................... 106
7.2.1 Experimental Results ........................... 107
7.2.1.1 Results from NDT ...................... 107
7.2.1.2 Results from short-beam bending ....... 109
7.2.2 FE-models from 3D-CT data - real structure
modelling ...................................... 110
7.2.3 FE- and experimental results ................... 111
7.3 Fracture mechanical modelling of desiliconized
C/C-SiC with delaminations ............................ 114
7.3.1 Experimental Results ........................... 115
7.3.1.1 Results from NDT - sample taking ...... 115
7.3.1.2 Results from bending test ............. 116
7.3.2 Simplified 2D-FE-models based on 3D-CT data .... 120
7.3.3 FE- and experimental results .................... 122
8 Discussion ................................................. 131
8.1 Interlaminar manufacturing defects in C/C-SiC
material .............................................. 131
8.2 Modelling of tensile and bending behaviour ............ 131
8.3 Interlaminar fracture mechanics ....................... 136
8.4 Modelling of C/C-SiC with delaminations ............... 137
9 Summary and conclusions .................................... 139
Literature .................................................... 141
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