PSI - Issue 12

Simonetta Boria et al. / Procedia Structural Integrity 12 (2018) 317–329 Simonetta Boria et al./ Structural Integrity Procedia 00 (2018) 000 – 000

326 10

2

2

   

        

   





n

s

1



(1)

NFLS

SFLS

where NFLS is tensile failure strength and SFLS is shear failure strength of the adhesive. An adhesive material with the properties of NFLS = 50 MPa and SFLS = 40 MPa was chosen, being typical properties for epoxy adhesives usually used in structural applications. In order to capture the damage evolution during the impact of the external composite skins the MAT54 (MAT_ENHANCED_COMPOSITE _DAMAGE), which is based on Chang-Chang failure criterion (Chang et al. (1987), Choi et al. (1991)), was used. The Chang-Chang failure criteria for MAT54 can be summarized as follows:

 Tensile fiber failure mode:

 aa >0 then

2

0 failed 0 elastic

1         ab      c S 

aa       t X 

2

e





(2)

f

After failure E a =E b =G ab =  ab =  ba =0;  Compressive fiber failure mode:

 aa <0 then

2

0 failed 0 elastic



  

1    

X 

2

aa

e



(3)

 

c

 

c

After failure E a =  ab =  ba =0;  Tensile matrix failure mode:

 bb >0 then

2

2

0 failed 0 elastic

1                      bb ab t c Y  S

2 m

e

(4)

After failure E b =  ba =0  G ab =0;  Compressive matrix mode:

 bb <0 then

2

2

2

   

   

0 failed 0 elastic



2 bb           c c     c Y S S 2

  

bb   Y S 

2

ab

e

1

1  





(5)

c    

d





c

After failure E b =  ab =  ba =0  G ab =0;