ElastoDict-Deformations can be used to determine matrix damage in a composite model. In this example, E-Glass fibers are combined with an epoxy matrix. The structure used for this example is generated with FiberGeo.

Select Deformations from the pull-down menu in the ElastoDict module section.

In the Large Deformation Options dialog, under the Constituent Materials tab, set the materials to Epoxy (3501-6) with the Damage (UMAT) material model and Glass with the E-Glass (Isotropic) material model. The Failure Stress option for Glass can additionally be enabled, although it is not necessary for this example.

Under the Macroscopic Load Case tab, the experiment is set to Uniaxial Experiment - Tensile. A maximal strain of 0.6 % is applied in 30 steps (choose Predefined Shape, set Magnitude to 0.6 %, Length to 0.6 s and the Number of Steps to 30. Click apply to set the load in the Load Table). For damage simulations, it is useful to choose small steps (here, 0.02 %).

Under the Geometry Handling tab, keep the default settings.

Under the Solver tab, set the method to Fast (Conjugate Gradient). Keep the Tolerance at the default of 0.0001 since a high accuracy is important, especially for simulations with damage.

Under the Output tab, uncheck Write Deformed Geometry since generating the deformed geometries takes additional computation time and the deformed geometries are not relevant in most damage simulations (since the strain at the point of failure is often very low).

Analogously, writing volume fields might take a significant amount of disk space and time, depending on the size of the structure. Some disk-space and computational time is saved by unchecking stress, strain, and displacement fields which do not need to be visualized. Therefore, keep only the volume fields Stress - Von Mises and Strain – Von Mises and the Material State Variables (containing the damage and failure variables in this example).

Click OK to close the Options dialog and start the simulation by clicking Run in the GeoDict GUI main screen.

After the simulation is finished, the result file is opened automatically in the Result Viewer at the Results - Report subtab.

Under the Results - Plots subtab, the results of the deformation during the time series experiment are plotted as Stress-Strain chart (X-Axis: Strain Z-Dir; Y-Axis: Stress Z-Dir). Increasing damage leads to decreasing stiffness in the structure.

Choose Material00_Damage for the Y-Axis and click Apply… to plot the average matrix damage in the the matrix material (0 is no damage, 1 is maximal damage).

As it can be observed in the plot, the average damage increases constantly until the point of failure (which can be recognized on the drop in the stress-strain curve at a strain of 0.56 % in the plot above), but it reaches a plateau (with a much smaller increase) after failure. Failure in a composite is a local phenomenon: As soon as a crack occurs (with a high local damage), the rest of the structure is unloaded.

Other graphs of interest can be plotted by changing the selections of the X-Axis and the Y-Axis pull-down menus.

The original structure can be loaded with the Load Structure button.

The Strain/Stress Visualization tab contains the volume fields of the Time Steps, which can be selected from the pull-down menu (here, the point of failure at 0.56 s is selected) and loaded by clicking Load.

The components whose results can be visualized are checked in the list e.g., here von Mises Strain, von Mises Stress, Damage (Damage_0) and failure (failure_1). The numbers (0 in Damage_0 and 1 in failure_1) stand for the Material IDs to which the volume fields belong.

Click OK, to load the components.

In 2D and 3D Rendering, a color bar appears to the right (default position) during the visualization of the result file, indicating the gradation of the selected component.

Further visualization parameters can be set under the Volume Field tab, in the Visualization panel above the Visualization Area. For more information, please refer to chapter Visualization.

The crack in the material can be best visualized with the Transparency option for the volume field. For this, set the transparency as shown in the screenshot below: Choose low values (e.g. 0.2) for low damage values (in this example, for damage values lower than 0.75), and high values (1, which means no transparency) for high damage values (here, for damage values above 0.875).