Using cohesive elements

[hillasg]

I need to model a sandwich plate, and use cohesive elements for the adhesive between the core and the skin.
The core is a 3D plate with solid elements.
The skin is a thin plate - shell elements.
What is the right approach to connect them with cohesive elements? I created separate parts for the core and for the skin.
Do I need to create another part for the cohesive elements? I tried by creating a shell like part, but it will not accept cohesive ellemnts.

Please advise.

 

[bassmanjax]

Hi

Section 21.1 ot the CAE Users Manual covers the cohesive elements quite nicely.

Looks like you need to define the cohesive layer as a 3D solid part (see section 21.1.3) and then mesh it with cohesive elements.

Regards

Martin

Martin Stokes CEng MIMechE

 

[hillasg]

Defining a Solid part yields a choesive layer with fininte thickness. In the manual it is mentioned that cohesive elements can be used to model infintely small (zero) adhesive layers. How is that?

 

[bassmanjax]

I don't think it is possible to have a 'zero thickness' cohesive element but you can have a very thin element - the manual suggest a minimum geometrical thickness of 10e-4 with the actual thickness being defined in the Initial Thickness field of the cohesive section (*COHESIVE SECTION, THICKNESS=SPECIFIED).

The 3D cohesive elements look like they have an upper and lower face, hence they need to be defined in a 3D solid part.

Regards

Martin

Martin Stokes CEng MIMechE

 

[brep]

Zero thickness cohesive elements can be created manually using orphan mesh techniques. First create a shell orphan mesh part for the cohesive element layer (perhaps by create a shell part , mesh it with shell elements, then create an orphan mesh of from this). Next, use the mesh edit feature to create an offset solid mesh. The offset distance will be 0.0. make sure you use the options given to create surfaces on the top and bottom of the zero thickness cohesive layer so you can tie it to the the rest of the model.

NB Even though the cohesive layer must be an oprhan mesh to use this technique, it does *not* mean the rest of the assembly has to be an orphan mesh. You can quite happily tie (or whatever) the orphan mesh to a geometric part...

 

[muffiny]

Hi
WOW . . . I was modelling blast loading of a sandwich panel for my dissertation last year using cohesive elements.I had a skin,resin,core,resin,skin configuration. I created a 3-D part for the skin, resin and core.Cohesive elements were assigned to the resin section.I tied the skin to the resin and the resin to the core.For the thickness of the resin section, the smallest Abaqus would allow was 10e-4
regards
melody(newbie to Abaqus)

 

[abhaynaik]

hi "brep"...thanks for your replies...i think you can help me with my problem....

I am working on a simple cohesive section problem.. I tried to work along the guidelines provided in v6.6 manual section 21, to create cohesive section by embedding in the previously meshed model.

My problem with this model is...I want to use a single part for the entire model and don't want to go for 2 or more parts....When I use the offset tool to offset the solid mesh to create zero thickness or even finite thickness cohesive section, the original node pairs are not disconnected. I thought I could add the cohesive zone in between already existing mesh. This way I could break the node connection at a surface and add this new cohesive zone in it.

I need help with this...I would appreaciate your help...

Thanks