Towards the size estimation of a Representative Elementary Domain in semi-crystalline polymers

•RVE size has never been quantified for semi-crystalline polymers.•Size of a Representative Elementary Domain for the macroscopic strain was determined.•It was made possible by recent microstrain-fields obtained from in-situ DIC in a SEM.•A statistical method was applied, associating the RED size with a wanted precision.•For the tested precisions, RED size notably exceeds the size of one single spherulite.

Like in any heterogeneous material, predicting the macroscopic mechanical behavior of semi-crystalline polymers from scale transition approaches requires to estimate the size of a Representative Volume Element (RVE). However, no quantitative estimation has been reported so far in the literature for these materials. This study is a step forward, by estimating the minimal domain over which the microscopic strain must be spatially averaged to match the macroscopic strain, in a stretched linear low-density polyethylene. A statistical RVE determination method inspired from the work by Kanit et al. (2006) was applied to strain fields acquired at the spherulitic scale from in-situ Digital Image Correlation in a Scanning Electron Microscope. Results show that the size of a representative domain significantly exceeds the size of a single spherulite. Several spherulites are actually contained, depending on the wanted estimation accuracy and on the number of realizations one is ready to generate.