Low Density Polyethylene (LDPE) exhibits extensive molecular branching. This causes a low density, often between 0.910 and 0.930 g/cm3. Linear Low Density Polyethylene (LLDPE) has more short branches, enhancing the intermolecular deformations, which reduces the modulus and makes the material more viscoelastic. If you are interested in using a high quality non-linear viscoplastic material model for a generic LLDPE then consider using the option that is available in the PolyUMod Material Database.
Here is the experimental data that was used to calibrate the material model in the PolyUMod Material Database. The experimental data contains monotonic tension at 2 strain rates, and cyclic tension with stress relaxation segments. This type of test is a “smart test“.
Material Model Calibration
Database Material Model
To use the LLDPE material model first open the material model selection dialog in MCalibration, and then select “MaterialDB-LLDPE”.
Then, as an optional step, you can explore the predicted behavior of the LLDPE material model using virtual experiments in MCalibration. This figure shows the predicted stress-strain response at 6 different applied strain rates in uniaxial tension.
Finally, just export the database material model to the desired FE solver format. Then read in that exported material model and run any FE simulation. That is all there is to it!