Issue 61

K. Belkaid et alii, Frattura ed Integrità Strutturale, 61(2022) 372-393; DOI: 10.3221/IGF-ESIS.61.25

3     u z

3 

0

(2)

3            u u u u z y y z 3 3     2   3            u u u u z x x z 3 3     1   3 3    u u 1             u u y x x y 2  

0   

2 2  4

4 

z

4

0   

2 2  5

5 

z

5





0

0   z 2 2

6     z 6

6 

6

where:

 



2













u x

w

4 h

0

0

2

x

x

1 

1 

1 





 

 

;

;

2

2





    x x

x

3







 



2





u

w

4 h

y

y

0

0

2

2 

2 

2 





 

 

;

;



2

2





    y y

y

y

3

 







w

w

4

0  

2

4 

    y

 

 

;

y

4

2



  y

y

h

 

    w x

w x

4

 

0  

2

 

5 

 

    x

;

x

5

2

h



  

        u v w w x x y y

y

0

0 6 ; 

  x

  

6 

;

  y

x





  

  

2







w

4 h

y

2

x

6 

 

 

2

2

  y

 

x

x y

3

C ONSTITUTIVE EQUATIONS

T

he laminate is usually made of several orthotropic layers (Fig 1). Each layer must be transformed into the laminate coordinate system (x, y, z) [2]. The stress–strain relationship is given as:

              xx yy xy

             xx yy xy

    

    

11 C C C C C C C C C 12 12 22

16

         xz yz

        xz yz

  

  

44 C C C C 45

45

;

(3)

26

55

k

k

16

26

66

k

k

where ij C are the transformed material constants:

375