Cohesive element distorted

[Manh26]

Hello everyone.
I'm doing simulation about impact on composite using cohesive element. I have composite (0/90/0) which were modelled throug their thickness with C3D8R, while COH3D8 cohesive elements were inserted at the two interfaces between layers with different orientation. Interaction between intender and plate is surface-to-surface contact. After caculation, my cohesive element is distorted like this.

Can someone help me solve this problem ?

 

[FEA way]

Interaction between intender and plate is surface-to-surface contact.

Why aren'y you using general contact ? It's the appropriate type of contact for such cases.