Nanovoid morphology and distribution in deformed High Density PolyEthylene observed at the nanometric scale
Résumé
In semicrystalline polymers, cavitation is identified as a main damage phenomenon and is brought to light by whitening of the sample appearing under loading. The aim of this study was to investigate nano-cavitation in deformed High Density PolyEthylene (HDPE). In a recent publication [1], 2D Fast Fourier Transform analysis (2D-FFT) was applied to reconstructed tomographic sections to determine damage anisotropy. Using a resolution limit close to the size of damage features, cavitation was not observed during deformation even in the necking region: The change of the observed signal was related essentially to macromolecular rearrangement without any voiding.
In the present study, magnified synchrotron radiation holotomography [2] was used to highlight the existence of permanent nano-voids within the spherulitic microstructure of HDPE. Image processing, 3D image segmentation and 2D-FFT, were shown to lead to quantification of void volume fraction, void size distributions and characteristic dimensions. Nanovoid morphology and distribution in HDPE reveals to be similar to cavitation mechanisms in other semi-crystalline polymers.
[1] A. Blaise, C. Baravian, S. Andre, J. Dillet, L. J. Michot, and R. Mokso. Investigation of the mesostructure of a mechanically deformed hdpe by synchrotron microtomography. Macromolecules, 43(19):8143–8152, 2010.
[2] G. Requena, P. Cloetens, W. Altendorfer, C. Poletti, D. Tolnai, F. Warchomicka, and H. P. Degischer. Submicrometer synchrotron tomography of multiphase metals using kirkpatrick–baez optics. Scripta materialia, 61(7):760–763, 2009.