Chapter 12: Interface Delamination and Failure Simulation
An interface exists anywhere two materials are joined together. The interface between the layers of a
composite structure is of special interest, because when this type of structure is subjected to certain
types of external loading, the failure process (delamination) takes on a unique character. Interface
delamination is traditionally simulated using fracture mechanics methods, such as nodal release technique.
Because cracks generally grow along the interfaces, VCCT-based crack growth simulation has become
a widely used technique for simulation of interface delamination of laminate composite. This technique
is also well suited for modeling the fracture process in a homogeneous medium, as fracture can be
considered a separation process between two surfaces. For more information, see VCCT-Based Crack
Growth Simulation (p. 381).
Alternatively, you can use the cohesive zone model to simulate interface delamination and other fracture
phenomena. This approach introduces failure mechanisms by using the hardening-softening relationships
between the separations and incorporating the corresponding tractions across the interface. Similarly,
this technique is also well suited for modeling the fracture process in a homogeneous medium. An in-
terface delamination and failure simulation is performed by first separating the model into two com-
ponents or groups of elements, then defining a cohesive zone between the two groups. Two options
are available for modeling the interface:
- Modeling Interface Delamination with Interface Elements (p. 397)
- Modeling Interface Delamination with Contact Elements (p. 404)
12.1. VCCT-Based Crack Growth Simulation
The virtual crack closure technique (VCCT) was initially developed to calculate the energy-release rate
of a cracked body [ 6 ]. It has since been widely used in the interfacial crack growth simulation of laminate
composites, with the assumption that crack growth is always along a predefined path, specifically the
interfaces [ 7 ][ 8 ][ 9 ][ 10 ].
VCCT-based crack growth simulation is available with current-technology linear elements such as
PLANE182 and SOLID185.
A VCCT-based crack growth simulation involves the following assumptions:
- Crack growth occurs along a predefined crack path.
- The path is defined via interface elements.
- The analysis is quasi-static and does not account for transient effects.
- The material is linear elastic and can be isotropic, orthotropic or anisotropic.
The crack can be located in a material or along the interface of the two materials. The fracture criteria
are based on energy-release rat es calculated using VCCT. Several fracture criteria are available, including
a user-defined option. Multiple cracks can be defined in an analysis.
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