Abaqus UGENS/UMAT for composites damage

A discrete damage mechanics (DDM) model is now available as a UGENS/UMAT implementation for Abaqus/standard. This is an analytic constitutive model for laminates composites, based on discrete fracture mechanics. It is capable of predicting matrix crack initiation and crack density evolution using just two parameters--the critical energy release rates (ERR) in opening mode I and shear mode II. A methodology is available to determine those (invariant) material properties from experiments. 

In situ efects are automatically delivered without any correction or effort necessary. Stress softening and strain hardening are automatically delivered without any need for additional material parameters such as hardening exponents or anything like that. You don't need the transverse tensile strength F2t and shear strength F6 of the lamina, because the damage initiation is taken care by the ERR. The damage evolution is also taken care by the ERR. The method works for any symmetric laminate, with any an all laminas capable of damaging. The model is strongly mesh independent (no need to use a characteristic length) and it captures (directional) localization. 

The theory is described in "Barbero, E. J. and D. H. Cortes, A Mechanistic Model for Transverse Damage Initiation, Evolution, and Stiffness Reduction in Laminated Composites, Composites Part B, Web: Oct. 8, 2009 as http://dx.doi.org/10.1016/j.compositesb.2009.10.001, print:  41(2) 124–132, March 2010"

The use of the UGENS/UMAT is explained in Chapter 9 of "Finite Element Analysis of Composite materials Using Abaqus",   http://barbero.cadec-online.com/feacm-abaqus/index.html

The .obj is available from http://barbero.cadec-online.com/feacm-abaqus/Examples/Chapter_9/Ex_9.1/ 

The implementations has been validated with all freely available, pertinent experimental data, as well against numerically "exact" results from 3D discretization, see "E. J. Barbero and F. A. Cosso, Benchmark Solution for Degradation of Elastic Properties due to Transverse Matrix Cracking in Laminated Composites, Composite Structures, 98(April 2013), 242–252, http://dx.doi.org/10.1016/j.compstruct.2012.11.009"