Issue 51

B. Zaoui et alii, Frattura ed Integrità Strutturale, 51 (2020) 174-188; DOI: 10.3221/IGF-ESIS.51.14

towards the fiber is characteristic of this propagation kinetics variation of the crack. When the crack crosses the entire fiber and tends towards the second interface, this speed is again slowed down by the strong crack-interface interaction. This behavior is all the more marked as the commissioning stress is more intense.

80

70

Fiber

Matrix

60

20 K I ( MPa.mm 1/2 ) 30 40 50

 = 50 MPa  = 80 MPa  = 120 MPa

10

0

0,000

0,005

0,010

0,015

0,020

0,025

a (mm)

Figure 8: Effect of the commissioning stress intensities on matrix crack propagation in mode I.

10

150

b)

a)

Fiber

Matrix

100

Matrix

Fiber

8

2 K II ( MPa.mm 1/2 ) 4 6

50

-100 I ( MPa.mm 12 ) -50 0

 T=400°C,  =120MPa  T=600°C,  =80MPa  T=800°C,  =50MPa

 T = 400°C,  = 120 MPa  T = 600°C,  = 80 MPa  T = 800°C,  = 50 MPa

K

-150

0

-200

0,000

0,005

0,010

0,015

0,000

0,005

0,010

0,015

a (mm)

a (mm)

1,0

c)

0,5

Matrix

Fiber

-1,5 III ( MPa.mm 12 ) -1,0 -0,5 0,0

 T = 400°C,  = 120 MPa  T = 600°C,  = 80 MPa  T = 800°C,  = 50 MPa

K

-2,0

-2,5

-3,0

0,000

0,005

0,010

0,015

a (mm)

Figure 9: Variation of the stress intensity factor according to applied thermomechanical stresses intensities. a) in mode I, b) in mode II, c) in mode III.

184