Mechanical properties of flexible graphite: review

Flexible graphite is commonly used in a various range of applications in which high resilience, high thermal stability and chemical resistance are requested. Such material is obtained as the last stage of compression of exfoliated graphite flakes without any additive binder and its density is fundamental in determining all the mechanical, thermal and electrical properties. During the compression, the worm-like units interlock among each other by only friction forces and build connected clusters or structural units that retain their shape during the load application. The orientation of the latter changes together with the increase on density and gives an higher grade of anisotropy among the in-plane and out-of-plane directions. This process leaves a fraction of void volume that decreases together with the compaction pressure. A certain level of inherent porosity is therefore always present; this, together with the low thermal expansion comparable to that of metals, make such material excellent on dissipate deformation energy by mean of sliding among graphite layers. For the same reasons, the applications in the mechanical field request mainly the ability of work absorption in compression loading, like in sealing and dumping and moreover the visco-elastic properties are remarkable and comparable to those of rubbery materials. In this work an overview is given about the microstructure changing during the compression of the expanded phase and its effect on the main mechanical properties. The values of the principal properties available in literature are compared.