Understanding the Samcef cohesive element (Simcenter Samcef)

Cohesive elements represent a homogeneous resin layer that ensures the interlaminar stress transfer between adjacent composite plies.

To model this interface layer, Samcef uses 3D quadratic 20-noded bricks (T147 element) or 15-noded wedges (T145 element) with a zero thickness.

Interface elements simulate perfect bonding between layers. Therefore, when including them in a finite element model, a major prerequisite is that no additional deformations occur due to their presence. Therefore, sufficiently high dummy stiffness values for the cohesive element must be supplied, but depending on the applied numerical integration scheme, this may result in undesired spurious oscillations of the stress field. In this regard, the Lobatto integration scheme led to correct and stable results for a wide range of cohesive elements uses. The Lobatto integration scheme is the default for the T147 brick element, while the classical Gauss integration scheme is used for the T145 wedge.

The cohesive element ensures displacements and stresses transfer between adjacent faces. Various damage models can also be associated to this element to simulate more or less complex delamination damage mechanisms.

This element cannot receive any element loads. It does not contribute the model's mass matrix and generates interlaminar stress tensor as result.

Note:

For more details on these elements, see the T145 and T147 element mathematical models in the Simcenter Samcef structure library documentation.

How do I

Create a cohesive layer

Learn more

Understanding the non-local behavior for solid laminates (Simcenter Samcef)

Ply-based workflow

Defining plies and a stacking sequence

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Understanding the Samcef cohesive element (Simcenter Samcef), Simcenter 3D 2021.1 Series

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