K. Honjo Carbon 41(2003)979-984 Mirror radius: rH / um 21.51 0.5 abraded etched 84730 T800H ◇ line is for A=22MPa·m12 A (rH1m)-12 Fig. 3. Tensile strength vs. mirror radius for T300 and T800H carbon fibers, which fractured from filament surface. Circle: mechanically abraded or as-obtained, square: chemically damaged during deposition of TiC or TiN, which were removed by dissolution before testing. A line for 4=2.2 MPam is shown in the figure close to the value for the T300 and T800H fibers in the MPam". Corresponding I values are close to the 2yce present stud value estimated from the y value for a graphite crystal The Kic values re-estimated for the old PAN-based fiber in Whitney and Kimmel's paper are also close to the 4. Conelusions observed values. These K values are similar to those of polycarbosilane based SiC fibers (I MPam")[4, 5 and The Kic values of the PAN-based high strength type silicate glasses(ca 0.7 MPam")[6], and also to that of T300 and T800H carbon fibers are found to be polycrystalline graphite (1 MPam)[7 Table 2 Re-estimated Kic for the fibers in Whitney and Kimmel's paper 3] Identity y value"(Ref. [3]) Kc value for y in Ref [3] Re-estimated Kc; rH/e=6 name with F=l(m)(MPam) and F=0.75(MPam") 2.7 HT-S D 43439 Ref. 20 1.8and3.2 The fibers are assumed to be isotropic in Ref. [ 3] Celanese Research Company Great Lakes Carbon Co The filaments on Johnson's micrographs(Fig. 5a and b in Ref. [20)). Acrilan"( Chemstrand Ltd basedK. Honjo / Carbon 41 (2003) 979–984 983 Fig. 3. Tensile strength vs. mirror radius for T300 and T800H carbon fibers, which fractured from filament surface. Circle: mechanically abraded or as-obtained, square: chemically damaged during deposition of TiC or TiN, which were removed by dissolution before testing. A 1/2 line for A52.2 MPam is shown in the figure. 1/2 close to the value for the T300 and T800H fibers in the MPam . Corresponding G values are close to the 2gCF present study. value estimated from the g value for a graphite crystal. G The K values re-estimated for the old PAN-based fibers IC in Whitney and Kimmel’s paper are also close to the 4. Conclusions observed values. These K values are similar to those of IC 1/2 polycarbosilane based SiC fibers (1 MPam ) [4,5] and 1/2 The K values of the PAN-based high strength type silicate glasses (ca. 0.7 MPam ) [6], and also to that of IC 1/2 T300 and T800H carbon fibers are found to be |1 polycrystalline graphite (1 MPam ) [7]. Table 2 Re-estimated K for the fibers in Whitney and Kimmel’s paper [3] IC a Fiber Identity E s g u IC IC H value (Ref. [3]) K value for g in Ref. [3] Re-estimated K ; r /c56 22 1/2 1/2 name (GPa) (GPa) with F51 (J m ) (MPam ) and F50.75 (MPam ) b A – 255 1.3 14 2.7 0.8 c B 4T 271 2.6 31 4.1 1.3 d C HT-S 272 2.5 41 4.7 1.4 b D – 262 2.3 35 4.3 1.3 e E Ref. [20] 138 1.8 and 3.2 39 3.3 1.0 a The fibers are assumed to be isotropic in Ref. [3]. b Celanese Research Company. c Great Lakes Carbon Co. d Hercules, Inc. e The filaments on Johnson’s micrographs (Fig. 5a and b in Ref. [20]). Acrilan
(Chemstrand Ltd.) based