Abaqus Analysis User's Manual  


23.3.2 Damage initiation for fiber-reinforced composites

Products: Abaqus/Standard  Abaqus/Explicit  Abaqus/CAE  

References

Overview

The material damage initiation capability for fiber-reinforced materials:

Damage Initiation

Damage initiation refers to the onset of degradation at a material point. In Abaqus the damage initiation criteria for fiber-reinforced composites are based on Hashin's theory (see Hashin and Rotem, 1973, and Hashin, 1980). These criteria consider four different damage initiation mechanisms: fiber tension, fiber compression, matrix tension, and matrix compression.

The initiation criteria have the following general forms:

Fiber tension :

Fiber compression :

Matrix tension :

Matrix compression :

In the above equations

denotes the longitudinal tensile strength;

denotes the longitudinal compressive strength;

denotes the transverse tensile strength;

denotes the transverse compressive strength;

denotes the longitudinal shear strength;

denotes the transverse shear strength;

is a coefficient that determines the contribution of the shear stress to the fiber tensile initiation criterion; and

are components of the effective stress tensor, , that is used to evaluate the initiation criteria and which is computed from:

where is the true stress and is the damage operator:

, , and are internal (damage) variables that characterize fiber, matrix, and shear damage, which are derived from damage variables , , , and , corresponding to the four modes previously discussed, as follows:

Prior to any damage initiation and evolution the damage operator, , is equal to the identity matrix, so . Once damage initiation and evolution has occurred for at least one mode, the damage operator becomes significant in the criteria for damage initiation of other modes (see “Damage evolution and element removal for fiber-reinforced composites,” Section 23.3.3, for discussion of damage evolution). The effective stress, , is intended to represent the stress acting over the damaged area that effectively resists the internal forces.

The initiation criteria presented above can be specialized to obtain the model proposed in Hashin and Rotem (1973) by setting and or the model proposed in Hashin (1980) by setting .

An output variable is associated with each initiation criterion (fiber tension, fiber compression, matrix tension, matrix compression) to indicate whether the criterion has been met. A value of 1.0 or higher indicates that the initiation criterion has been met (see “Output” for further details). If you define a damage initiation model without defining an associated evolution law, the initiation criteria will affect only output. Thus, you can use these criteria to evaluate the propensity of the material to undergo damage without modeling the damage process.

Input File Usage:          Use the following option to define the Hashin damage initiation criterion:
*DAMAGE INITIATION, CRITERION=HASHIN, ALPHA= 
, , , , ,

Abaqus/CAE Usage:   Property module: material editor: MechanicalDamage for Fiber-Reinforced CompositesHashin Damage

Elements

The damage initiation criteria must be used with elements with a plane stress formulation, which include plane stress, shell, continuum shell, and membrane elements.

Output

In addition to the standard output identifiers available in Abaqus (“Abaqus/Standard output variable identifiers,” Section 4.2.1, and, “Abaqus/Explicit output variable identifiers,” Section 4.2.2), the following variables relate specifically to damage initiation at a material point in the fiber-reinforced composite damage model:

DMICRT

All damage initiation criteria components.

HSNFTCRT

Maximum value of the fiber tensile initiation criterion experienced during the analysis.

HSNFCCRT

Maximum value of the fiber compressive initiation criterion experienced during the analysis.

HSNMTCRT

Maximum value of the matrix tensile initiation criterion experienced during the analysis.

HSNMCCRT

Maximum value of the matrix compressive initiation criterion experienced during the analysis.


For the variables above that indicate whether an initiation criterion in a damage mode has been satisfied or not, a value that is less than 1.0 indicates that the criterion has not been satisfied, while a value of 1.0 or higher indicates that the criterion has been satisfied. If you define a damage evolution model, the maximum value of this variable does not exceed 1.0. However, if you do not define a damage evolution model, this variable can have values higher than 1.0, which indicates by how much the criterion has been exceeded.

Additional references