Carbon fibers average moduli

Type of carbon fibers Average diameter (pm) Average length (mm) Specific gravity (20°C) Elastic modulus in tension (GPa) Tensile strength (MPa)... 

Mesophase pitch-based carbon fibers generally have the highest stiffness of all carbon fibers with modulus of elasticity up to 965 GPa (140 Msi), considerably higher than PAN-based fibers. The tensile strength however is much lower, averaging only half. As mentioned in the previous section, the compressive-failure strain is low. 

However, other factors, particularly the presence of flaws, may limit the observed strength. From selected PAN based carbon fibers, Diefendorf and Tokarsky determined an experimental average value of (2y /Jtc) = 4650N /m (=56 psi ). Hence, the relationship between modulus and tensile strength at break, for PAN... 

Zussman et al. [108] measured the mechanical properties of single carbon nanofibers introduced in subsection 10.4.1. The average bending modulus of nanofibers were 63 7 GPa and the failure stress was between 0.32 and 0.9 GPa, where failure occurring at the gauge region. Carbon fibers were prepared from PAN homopolymers, hence it is not easy to compare with carbon microfibers based on PAN copolymers. They also carried out Weibull-analysis which gave a failure stress of 640 MPa where 63% of nanofibers would break with a confidence interval of 95%. 

Figure 8.2. Specific strength and modulus of carbon and other fibers (average values from manufacturers data).

Carbon fibers based on isotropic pitch have low strength and modulus with tensile strength averaging 870 - 970 MPa and modulus of 40 - 55 GPa (Datafrom Carboflex, Ashland Oil Co., Ashland, KY, and Kureha Chemicals, Japan). 

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