Compaction of the core of plasterboard is one of the limiting phenomena for its mechanical performance. This mechanism is studied in a (standardized) nail-pull test and an indentation test. A cylinder made of foamed gypsum is indented in-situ in an X-ray lab tomograph with a nail or a sphere of millimeter radius. The experiments show that foamed plaster displays a sharp transition between an undamaged state (with a linear elastic behavior) and a compacted state with collapsed porosity under the indenter. Tomographic acquisitions of the sample under load associated with a global version of Digital Volume Correlation allow displacement fields to be measured at different load levels. However, because of the heterogeneous nature of the tests, a fine spatial resolution of the displacement fields is required to measure the strains at the crushing limit. A dedicated procedure exploiting computed displacement fields within the digital volume correlation procedure is utilized. It allows for the quantification of stress fields that are post-processed to identify the crushing criterion. It is shown that this analysis is consistent with more macroscopic oedometric and compression tests.

References

Bouterf A., Comportement mécanique de la plaque de plâtre étudié par tomographie et essais mécaniques insitu,
PhD thesis, ENS Cachan (2014).
Bouterf A., Roux S., Hild F., Adrien J., Maire E., Meille S., Digital volume correlation applied to X-ray
tomography images from spherical indentation tests on lightweight gypsum, Strain, 50(5), 444-453 (2014).
Bouterf A., Adrien J., Maire E., Brajer X., Hild F. Roux S., Failure mechanisms of plasterboard in nail pull test
determined by X-ray microtomography and digital volume correlation, Experimental Mechanics, submitted
(2016).