1. 36. Sheaffer P. M. , in Proceeding and Program of Carbon 1987, edited by Thrower P.A. , (American Carbon Society 1987). pp. 20–21.
2. 31. Reference 5 lists data for P-25,P-55,P-75,P-100 and p-120. The nonlinear elasticity of P-25 is not included in Table 1. The large observed NLE at 23 °C (97 GPa at a stress of 0.11 MPa) less the predicted NLE (44 GPa at the same stress) yields a residual NLE of 53 GPa. This suggests that a third mechanism might be operating in this sample. The increase of the NLE of P-55 and P-75 with temperature is consistent with this hypothesis. That for P-55 approaches that of P-25 at 210 0 C and that for P-75 has increased considerably at 450°C1,5,18,19. Thus, there might be another mechanism of NLE which is a function of temperature as well as some of the parameters which vary with fiber processing (crystal size, orientation, perfection, c dimension, etc). For example motion and pinning of basal dislocations have been considered11,32,33. The modulus given in the last two references is observed to increase in the same temperature range as that for the pitch-based fibers in the present work1,5,14,15. The results for P-120 are not included in Table 1 because all the experimental errors would make the uncertainty of the residual value to be used for column three too large.
3. Calculation of polymer elastic moduli using semiempirical methods