Issue 60

A. Deliou et alii, Frattura ed Integrità Strutturale, 60 (2022) 30-42; DOI: 10.3221/IGF-ESIS.60.03

         2 X Y

4 1 1

1

2

2

T

S

The coefficient K is then:

      2 2 1 1 K Y X XY X Y S T    

(6)

Tsai-Wu criterion We will retain the Tsai-Wu criterion       1 , F F i j



 

1, 6

(7)

ij i

j

i i

where the constants i F and ij F are the components of two tensors, respectively of rank 2 and 4, with the parameters ij F [32,33]:

1 1 X X

  1

F

t

c

1 1 Y Y

  2

F

t

c

1

 11

F

X X

t

c

(8)

1

 22

F

t c Y Y

1





F

F

0 and

6

66

2

S

1 2

 12

F

F F

11 22

X t , X c : Ultimate tensile strengths along the longitudinal axis, in tension and compression respectively. Y t , Y c : Ultimate tensile strengths along the transverse axis, respectively in tension and in compression. S : Stress at failure in shear, in the plane of the layer. Maximum stress criterion This criterion states that the structure withstands the conditions of use if the calculated stresses meet the conditions below.     11 c X t X

    22 c Y

t Y

(9)

  12 S

33