抄録
Flexible graphite sheets have hierarchy porous structure and show high ratio of recovery against compression. The outstanding recovery property caused by complex microstructure is very interesting. In this study, inhomogeneous strain distribution in flexible graphite sheet was investigated and characterized using synchrotron radiation microtomography. The synchrotron radiation microtomography is non-destructive inspection with approximately 1-2 μm resolution. It allows us 4D observation (i.e. 3D space + time) in fragile materials. The three-dimensional strain distribution in the interior of the specimen was obtained in series of microtomography images during compression and recovery by using the microstructural tracking method, which has been developed in our research group. The inner strain distribution indicated inhomogeneous deformation depending on flexible graphite sheet microstructure. After obtaining inner strain information, analysis to characterize deformation behavior was proposed and performed. In consequence, the grouping analysis based on principal strain direction in whole measurement points revealed that deformation units exist in the flexible graphite sheet. The size, shape and arrangement of the deformation units corresponded to exfoliated graphite worms, which making up the flexible graphite sheet. The exfoliated graphite worms would be rearranged during mechanical compression in production process of flexible graphite sheets. Anisotropic structure would cause heterogeneous mechanical response on each deformation unit. Microscopic deformations during compression and recovery are surely affected by the microstructure of the flexible graphite sheet.
