Tension–compression anisotropy of in-plane elastic modulus for pyrolytic carbon

We used standard strain gage methods to measure the anisotropic elastic constants for a sample of pyrolytic carbon. The in-plane elastic modulus exhibits significant tension–compression anisotropy −30.2 GPa in tension and 18.8 GPa in compression. The out-of-plane compressive modulus is 5.2 GPa and the Poisson’s ratios are ν12 = 0.35 (compression), ν23 = 0.16 (tension), 0.22 (compression), and ν21 = 0.97 (tension). The tension–compression anisotropy is attributed to buckling, puckering, or bending of the graphene sheets in compression versus simple stretching in tension. The in-plane to out-of-plane anisotropy is expected from the microstructural anisotropy.