Strain-Rate Effect on the Deformation Mechanisms of Agglomerated Cork

Cork is a multi-phased biosourced polymeric material. In this case study, it was agglomerated with a thermosetting resin by an uni-axial compression process. Agglomerated cork is nowadays considered for shock absorption applications. Therefore its behavior at high strain rates is of interest. The influence of the mean strain rate on the mechanical behavior of agglomerated cork and the associated strain mechanisms is studied here. Compression tests were performed in quasi-static (~4.2 × 10−3 s−1) and dynamic (~70 s−1) regimes. A specific assembly, the fly wheel, made it possible to obtain an almost constant loading rate during the test under dynamic conditions. As expected for a polymeric material, the Young’s modulus of the material and the energy absorbed at densification (elastic and dissipated) during compression strongly depend on the average deformation rate. Using the correlation of digital images (DIC), the deformation mechanisms involved during the different stress regimes could be observed. Deformations which are highly heterogeneous take the form of localization bands. In quasi-static conditions, these localization bands are observed near interfaces between grains. At a dynamic regime, however, deformations seem more diffuse.