21 High-Temperature Creep Damage Evolution of C/SiC …
247
Table 21.6 Values of cluster centers
Sample Cluster Average
frequency
Center
frequency
Peak
frequency
Frequency
band 1
Frequency
band 2
Frequency
band 3
Frequency
band 4
1
A
98.6
262.6
196.8
8.2
37
41
13
B
111.7
287.9
290.4
4.4
17
57
20
C
106.5
302.2
404.3
5.1
12
43
39
2
A
63
278
274
3
27
56
14
B
116
290
296
5
13
58
24
C
72
305
387
5
8
45
41
3
A
106.6
283
264
2
26
57
15
B
119.9
294
282.1
2
13
64
20
C
118.5
312.2
379.4
2
8
52
37
D
104
296
403.5
3
13
61
41
4
A
98
281
230
2
34
52
12
B
116
296
290
1
17
65
17
C
231
309
362
2
10
61
27
5
A
114.1
288.7
289.4
3
24
56
18
B
126.3
304.8
320.2
2
9
69
20
C
118
312.7
352.5
3
9
51
37
6
A
109.1
284.9
270.8
4
25
49
22
B
122.5
299.4
293.7
3
11
60
26
C
116.9
305.4
403.8
4
12
42
42
7
A
86.9
189.7
121.7
44
42
9
5
B
126.4
282.5
193.9
2
31
55
12
C
123
296.7
313.9
2
15
66
17
For such CMC materials, the type of damage can be obtained by SEM fracture
analysis. The C/SiC high temperature creep fracture surface with SEM observation is
as shown in Fig. 21.7. It is known that the C/SiC creep damages mainly are (A) matrix
cracking, (B) interface debonding (fiber extraction), and (C) fiber breakage. During
the creep process, the material absorbs energy with the development of damage propagation, and the material will be destroyed until the strain reaches the limit.. The
carbon fiber is the main carrier material in the C/SiC composites, which can characterize the breakage of the material, and the material is failed when it is destroyed
abundantly.
AE energy is usually assumed proportional to the energy dissipated by the source,
whatever the source mechanism. Hence the relationships between damages mechanisms and AE signals were established by analysis of energy, kinetics and location
of signals for each cluster during all the mechanical tests performed. The AE energy
distribution of different class is shown in the Fig. 21.8. The energy of class A signal
is the lowest and the distribution interval is narrow, and this kind of signal produces
the loading period, which corresponds to the characteristics of the matrix. The class
247
Table 21.6 Values of cluster centers
Sample Cluster Average
frequency
Center
frequency
Peak
frequency
Frequency
band 1
Frequency
band 2
Frequency
band 3
Frequency
band 4
1
A
98.6
262.6
196.8
8.2
37
41
13
B
111.7
287.9
290.4
4.4
17
57
20
C
106.5
302.2
404.3
5.1
12
43
39
2
A
63
278
274
3
27
56
14
B
116
290
296
5
13
58
24
C
72
305
387
5
8
45
41
3
A
106.6
283
264
2
26
57
15
B
119.9
294
282.1
2
13
64
20
C
118.5
312.2
379.4
2
8
52
37
D
104
296
403.5
3
13
61
41
4
A
98
281
230
2
34
52
12
B
116
296
290
1
17
65
17
C
231
309
362
2
10
61
27
5
A
114.1
288.7
289.4
3
24
56
18
B
126.3
304.8
320.2
2
9
69
20
C
118
312.7
352.5
3
9
51
37
6
A
109.1
284.9
270.8
4
25
49
22
B
122.5
299.4
293.7
3
11
60
26
C
116.9
305.4
403.8
4
12
42
42
7
A
86.9
189.7
121.7
44
42
9
5
B
126.4
282.5
193.9
2
31
55
12
C
123
296.7
313.9
2
15
66
17
For such CMC materials, the type of damage can be obtained by SEM fracture
analysis. The C/SiC high temperature creep fracture surface with SEM observation is
as shown in Fig. 21.7. It is known that the C/SiC creep damages mainly are (A) matrix
cracking, (B) interface debonding (fiber extraction), and (C) fiber breakage. During
the creep process, the material absorbs energy with the development of damage propagation, and the material will be destroyed until the strain reaches the limit.. The
carbon fiber is the main carrier material in the C/SiC composites, which can characterize the breakage of the material, and the material is failed when it is destroyed
abundantly.
AE energy is usually assumed proportional to the energy dissipated by the source,
whatever the source mechanism. Hence the relationships between damages mechanisms and AE signals were established by analysis of energy, kinetics and location
of signals for each cluster during all the mechanical tests performed. The AE energy
distribution of different class is shown in the Fig. 21.8. The energy of class A signal
is the lowest and the distribution interval is narrow, and this kind of signal produces
the loading period, which corresponds to the characteristics of the matrix. The class