Elastic Moduli of Pyrolytic Graphite

Abstract

The elastic moduli of pyrolytic graphite, a polycrystalline material exhibiting large elastic anisotropy, have been measured by the ultrasonic pulse-echo method. In units of 1011 dyn/cm2, they are c11 = 5.21, c12 = 1.88, c13 = 1.80, c33 = 2.58, and c44 = 0.15.

Nanoscale elasticity of highly anisotropic pyrocarbons

“…It is useful to compare the elastic constants of PyCs with those of graphite, which vary from %1 TPa in the basal direction (C 11 ) to %25 GPa in the transverse c direction (C 33 ). Experimental estimations of the transverse Young modulus obtained for high-textured PyCs are usually rather close to graphite's C 33 [6,8,9,7]. This is however usually not the case of in-plane properties.…”

“…This is however usually not the case of in-plane properties. Indeed, C 11 constants obtained using acoustic methods are in the range 40-50 GPa [6,7]; indentation moduli are around 10-30 GPa, i.e. lower or equal to the transverse values [8,12]; longitudinal moduli from tensile/compression tests show values ranging from around 20 GPa [11] as-prepared PyCs [10] and up to 400 GPa when heat treated at high temperature (2200°C) [10].…”

“…Nevertheless, a few studies report on the elastic properties of such PyCs as obtained by acoustic methods [6,7], micro and nano indentation [8,9] or uniaxial tension/compression tests [10,11]. High textured PyCs are isotropically transverse materials with a supposed high anisotropy of properties.…”

Effective stiffness and thermal expansion coefficients of unidirectional composites with fibers surrounded by cylindrically orthotropic matrix layers

“…Experimental and analytical studies (Böhlke et al, 2010;Gebert et al, 2010;Papadakis & Bernstein, 1963) show that elastic symmetry of PyC in the CVI infiltrated carbon/carbon composites can be approximately characterized as transverse isotropy with the symmetry axis located in the transverse plane passing through the fiber axis perpendicular to the fiber surface, see Fig. 2.…”

The Elastic Moduli of Thick Composites

“…can be written as h+~+"""h""-pw (l) (2) where u, v, and ware respectively the displacement components in z-, y-, and x-direction. The quantity pis the density of the material.…”