Compression behavior of natural graphite sheet

The compression behavior of natural graphite sheet (NGS) is studied during the forming process and during the compression of finished sheets. The forming process, in which the low-density semi-finished NGS is compressed to higher densities, is quantified by the proposed relationship p(f) = 0.35e(2.6d) where d is the free-standing density in g cm(-3) and p(f) is the forming pressure in MPa. The maximum achievable free-standing density is in the range 1.73-1.89 g cm(-3). The compression behavior of finished NGS is non-linear, hysteretic, and density-dependent with the maximum strain of 6% at 0.55 g cm(-3). The tangent compression modulus increases with the density and ranges from 20 to 220 MPa. A compact relationship for evaluating the strain at a given pressure and density is provided. NGS deforms viscously during the periods of constant pressure; the deformation is significant during the forming process but small during the compression of finished sheets.