You can model the delaminated region within a shell by either modelling it with shell elements such as shell 63 or solid elements such as solid 185. In case of modelling with shell elements you will have to create two parallel shells with all of their nodes merged except for the delaminated region. Similarly, in modelling with solid elements, a  cut should be produced within the cylinder, and the nodes of cut should not be merged with each other. then run your buckling analysis.

For modeling delamination in composite laminates, you can use FEA techniques.al you need to do is to adopt fracture mechanics technique by using Ansys of Abaqus. model a crack with a crack tip and propogation path.

you can model several layers of various materials using shell elements and in Sections command you can model the interface b y giving the orientation angles and thickness to those layers.

after meshing and analysing your model, just use elemental techniques to view the layers and elements at crack tip to measure stresses and strains.

good luck.

khurram

Instead of using a cohesive zone, there are a variety of node-release techniques, often based on the VCCT (virtual crack closure technique).

I know Abaqus has several built in functions to model cracks, presumably Ansys has the same?

thank you for helping 

but i dont want model crack tip.

i want model two layer with circular delamination in the mid plan. something like that i attach bellow.

In this case you have a 2D crack front, rather than a straight crack front / crack tip. You can still apply node-release techniques to such a case.

See e.g. Xie & Biggers, (2006), 'Strain energy release rate calculation for a moving delamination front of arbitrary shape based on the virtual crack closure technique. Part I: Formulation and validation', Engineering Fracture Mechanics, 73, 771-785

my project is analysis  the buckling of plate withe delamination not crack propagation.

i just want model  this crack (delamination) in ansys

thank u

You can model the delaminated region within a shell by either modelling it with shell elements such as shell 63 or solid elements such as solid 185. In case of modelling with shell elements you will have to create two parallel shells with all of their nodes merged except for the delaminated region. Similarly, in modelling with solid elements, a  cut should be produced within the cylinder, and the nodes of cut should not be merged with each other. then run your buckling analysis.

Hi there!!

I think method suggesteds by Mr. John-Alan Pascoe are suitable for your work , ansys 14 has got in built code to do the analysis but accessible through codes only, i been successful in modelling delamination of circular type for a cylindrical pipe,here's the link for process for isotropic you can easily extend this to composites.you can also visit ansys verification module for details 

https://www.youtube.com/watch?v=UMSOEknfNSk