12.3.3. Material Definition
12.3.3.1. Material Characteristics
ANSYS provides two cohesive zone material models with bilinear behavior to represent debonding. The
material behavior, defined in terms of contact stresses (normal and tangential) and contact separation
distances (normal gap and tangential sliding), is characterized by linear elastic loading followed by linear
softening. The slope of the curve depends on contact stiffness and a debonding parameter which is
defined in terms of material constants. Debonding allows three modes of separation:
- Mode I debonding for normal separation
- Mode II debonding for tangential separation
- Mixed mode debonding for normal and tangential separation
Debonding is also characterized by convergence difficulties during material softening. Artificial damping
is provided to overcome these problems. An option for tangential slip under compressive normal contact
stress for mixed mode debonding is also provided.
After debonding is completed, the surface interaction is governed by standard contact constraints for
normal and tangential directions. Frictional contact is used if friction is specified for the contact elements.
12.3.3.2. Material Constants
The cohesive zone material model with bilinear behavior (TB,CZM with TBOPT = CBDD or CBDE ) is
defined as:
= n n −τy= t y −and
τz= z −where:
P = normal contact stress (tension)
τy = tangential contact stress in y direction
τz = tangential contact stress in z direction
Kn = normal contact stiffness
Kt = tangential contact stiffness
un = contact gap
uy = contact slip distance in y direction
uz = contact slip distance in z direction
d = debonding parameterTo model bilinear material behavior with tractions and separation distances, use TB,CZM with TBOPT
= CBDD. You also input the following material constants with the TBDATA command:
Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential informationModeling Interface Delamination with Contact Elements