PSI - Issue 2_A

Stefano Bennati et al. / Procedia Structural Integrity 2 (2016) 072–079 S. Bennati, P. Fisicaro, P.S. Valvo / Structural Integrity Procedia 00 (2016) 000–000

77

6

b

a

c [mm]

90

90

B&K EBT

 = 1  = 1.0474  = 1.0776

75

75

30 35 40 50 60 90

60

60

 [deg]

 [deg]

45

45

30

30

15

15

0

1

2

3

4

25

35

45

55

65

1/3

c / l

a [mm]

Fig. 2. (a)  versus c / ℓ ; (b)  versus a for the values of c considered by Benzeggagh and Kenane (1996).

3. Delamination growth under quasi-static loads Under I/II mixed-mode fracture conditions, the critical energy release rate, G c , equals an intermediate value between those measured in pure modes I, G I c , and II, G II c . Many criteria for determining G c as a function of the mode-mixity are available in the literature. Here, we assume the following elliptical criterion:

2

2

I               c c G G G G II I II

1.

(13)

By expressing G I = G cos

2  and G

II = G sin

2  , in line with Eq. (9), it can be shown that Eq. (13) is equivalent to

1 2



   

   

4

4   sin

cos

  

.

(14)

G





c

2 G G

2 II

I

c

c

b

a

1600

400

Eq. (14) EBT

300

1200

2 ]

2 ]

200

800

G I [J/m

G c [J/m

100

400

Eq. (13) EBT

0

0 15 30 45 60 75 90 0

0

400

800

1200

1600

2 ]

G II [J/m

 [deg]

Fig. 3. (a) G I versus G II at the delamination onset; (b) G c versus  .