Damage Evolution

Control the evolution of damage after failure has been initiated.

When a composite material fails under tensile loading, cracks develop in the material that ultimately lead to separation of the material into two or more pieces, preventing the failed region from supporting any loading. However, when a composite material fails under compressive loading, the failed region can often support some level of residual load. As such, when a composite material fails in tension, the stiffness of that region is essentially zero while the stiffness of a region that fails in compression is still significant. A standard Helius PFA material does not capture this effect because the post-failure stiffness of the failed material is the same, regardless of the loading. This means the post-failure stiffness must be suitable for the anticipated loading. To overcome this, the *DAMAGE EVOLUTION keyword allows you to input fiber post-failure stiffness values (instantaneous degradation) or fiber critical fracture energies (energy-based degradation) for tensile and compressive loadings. This keyword must be preceded by the *MATERIAL keyword so that the material of interest is properly identified.

Instantaneous Degradation

*DAMAGE EVOLUTION, TYPE=DISCRETE
MPFS, FTPFS, FCPFS

Where MPFS is the matrix post-failure stiffness ratio, FTPFS is the fiber tension post-failure stiffness ratio and FCPFS is the fiber compression post-failure stiffness ratio.

Energy-Based Degradation

*DAMAGE EVOLUTION, TYPE=ENERGY
GCM, GCTF, GCCF

Where GCM is the matrix critical fracture energy, GCTF is the fiber tension critical fracture energy and GCCF is the fiber compression critical fracture energy.

Examples

*MATERIAL, ID=9001
*DAMAGE EVOLUTION, TYPE=DISCRETE
0.01, 1.0E-6, 0.1

*MATERIAL, ID=9002
*DAMAGE EVOLUTION, TYPE=ENERGY
15, 130, 180