## General Mechanical

#### Failure criteria used for MAT_059 ? I am modell thick composite want to use solid elements

• rahulb
Subscriber

LS-DYNA® KEYWORD USER'S MANUAL VOLUME II Material Models  doesn't give much information about the failure initiation equations used for MAT_059 for solid elements.

I want to know the following details:

1) Damage initiation criteria equations used in MAT_059.

2) How to add MAT_ADD_EROSION to account for element delition based on MAT_059 failure criteria.

• Andreas Koutras
Ansys Employee

Here is some information on the failure criteria of MAT_059 for SOLIDS.
The eight modes of failure and the condition that triggers each mode are:
1.Longitudinal tension:
sig1^2/xxt^2 + sig4^2/sba^2 + sig6^2/sca^2> 1.0
(sig1 positive)
2.Transverse tension:
sig2^2/yyt^2 + sig4^2/sba^2 + sig5^2/scb^2> 1.0
(sig2 positive)
3.Through-thickness shear (combined with long. tension):
sig1^2/xxt^2 + sig6^2/sca^2> 1.0
(sig1 positive)
4.Delamination (through-thickness tension):
sig3^2/zzt^2 + sig5^2/scb^2 + sig6^2/sca^2> 1.0
(sig3 positive)
5.Through-thickness shear (combined with transverse tension):
sig2^2/yyt^2 + sig5^2/scb^2> 1.0
(sig2 positive)
6.Longitudinal compression:
sig1^2/xxc^2> 1.0
(sig1 negative)
7.Transverse compression:
sig2^2/(sba + scb)^2 + (sig2 / yyc)*((yyc^2/(sba + scb)^2) - 1.0) + sig4^2/sba^2 + sig5^2/scb^2> 1.0
8.Through-thickness compression:
sig3^2/(sca + scb)^2 + (sig3 / zzc)*((zzc^2/(sca + scb)^2) - 1.0) + sig6^2/sca^2 + sig5^2/scb^2> 1.0

Scaling factors (ff1, ff2, ... ff8) are applied to the various components of stress when failure modes 1, 2, ..., 8, respectively, have been triggered.Once a failure mode * is triggered, it takes 100 time steps for ff* to go from a starting value of 1.0 to a final value of 0.0. The element is deleted when the condition sig1=sig2=sig3=0 is met.
Furthermore, you look for the papers:
"Crashworthiness Analysis with Enhanced Composite Material Models in LS-DYNA - Merits and Limits", Karl Schweizerhof et al, 5th International LS-DYNA User's Conference (1998).
"NUMERICAL SIMULATION OF DAMAGE PROPAGATION IN CFRP LAMINATES REPAIRED BY EXTERNAL BONDED PATCHES UNDER TENSILE LOADING", L.L. Peng et al, 18TH INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS.
Cheng. W; Hallquist. J. "Implementation of Three-Dimensional Composite Failure Model into DYNA3D". (mat_059_Hallquist_Cheng.pdf).
"A HIGH VELOCITY IIVIPACT PENETRATION NIODEL FOR THICK FIBER.REINFORCED COMPOSITES", S. Langlie and W. Cheng.

If you search online I'm sure you can find more information. I hope this helps.
• rahulb
Subscriber