Help searched: cohesive elements/cohesive surface

[StevenJS]

For my graduation project I’m working on a model to describe cracking behavior. For this model I want to model a fibre-epoxy interface, see the attached figure 1 (due to symmetry only a quarter is modeled). The fibre part is modeled with lineair elastic material. The epoxy part is modeled with CPS4 elements, with elastic behavior and MAXPS damage (damaged evolution included). The connection between the fibre and epoxy interface can be modeled with both a cohesive surface and cohesive elements. However cohesive surface will give inaccurate results due to peak stresses (see attached image 2).

For the attached image 2 I tested single cohesive elements, and two lineair elastic elements (very high E-module, thus these approach infinite stiffnes) connected with a cohesive surface.

Therefor I want to model the fibre-epoxy interface with cohesive elements instead of cohesive surfaces. I previously used a cohesive surface to model the interaction (before I found out about the inaccurate results). The cracking in the epoxy interface was modeled with XFEM. The results of the model where reasonable, however not completely correct. The normalized traction separation diagram is added in figure 3. However this normalized traction separation diagram should look as attached figure 4 as found by Alfaro and Suiker (2010).

Alfaro, M. Suiker, A. (2010) Transverse Failure Behavior of Fibre-epoxy systems, Journal of Composite Materials, Vol. 44, No. 12/2010.

So I tried to adjust the model, and change the fibre-epoxy interface from a cohesive surface to cohesive elements. When these cohesive elements are modeled the behavior of the model is however completely incorrect.

The input (.inp) files for both the cohesive surface and the cohesive element fibre-epoxy interaction are attached.

Why does Abaqus give completely different answers to the model when cohesive elements are used to model a fibre-epoxy interface.
And how can the model be adjusted to behave correctly.

Thank you in advance,
Any help would be very helpful!

Steven

 

[isyhadh]

can interaction and tie constraint happen/exist in the same time?
i have checked your cae file, it seems fine just you have to concern on the surface to surface contact/default

and how did you include the XFEM function?
many thanks
isyhadh

 

[isyhadh]

Dear Steven

can you advice
why I couldn't run the input file you attached
i run it ok, but the it turned out as aborted
can you advice why?
you said in the threads that you successfully run/simulated them

i think i want to give some advice on your traction values as well as tangential value that you need to specify
also the meshing is really essential for the cohesive element

please send your input file to my email
isyhadh82@gmail.com

so i can remedy and correct the meshing for you
many thanks

 

[StevenJS]

Hi Isyhadh,

Many thanks for your reply's!
I did just send you an e-mail with a reaction and the original files.

Hoping you will look into it!
Thanks in advance,

Steven