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The tensile properties and the Weibull statistical distributions of the tensile strength of poly-(para-phenylene-2,6-benzobisoxazole) (PBO), poly-(para-phenylene terephthalamide) (PPTA), copoly-(para-phenylene-3,4′-oxydiphenylene terephthalamide (PPODTA), polyarylate (PAR), and polyethylene (PE) polymeric fiber epoxy-impregnated bundle composites have been investigated. The results show that the Weibull modulus decreases as the tensile modulus, strength, and inverse of the failure strain increase. The interfacial shear properties were also examined using the microdroplet composite. For the lower interfacial shear strength of polymeric fibers, the Weibull modulus decreases as interfacial shear strength increases. Conversely, for the higher interfacial shear strength of polymeric fibers, the Weibull modulus increases as interfacial shear strength increases. Interestingly, these inflection points were also observed for the 20–30 MPa interfacial shear strength. [ABSTRACT FROM AUTHOR]

The tensile properties of polyacrylonitrile (PAN)-based and pitch-based single carbon fibers were assessed using Raman scattering. Parameters and ratios related to Raman scattering and stress measurement for the G- and D-bands were analyzed. These include the peak values of Raman shifts (RG, RD), full width at half maximum (FWHMG, FWHMD), peak value slopes (|AG|, |AD|), peak value intercepts (BG, BD), the intensity ratio (ID/IG), the peak value ratio (RD/RG), the full width at half maximum ratio (FWHMD/FWHMG), the slope ratio (AD/AG), and the intercept ratio (BD/BG). These parameters and ratios were determined by analyzing the PAN-based and pitch-based carbon fibers and were correlated to the tensile modulus (E), interlayer spacing (d002), lattice spacing (d10), and crystalline size (Lc and La). In addition, a linear relationship was identified between the Raman scattering, stress measurement parameters, ratios and E, d002, d10, as well as between the Raman scattering, stress measurement parameters, ratios and La and LC on the log–log scale. [ABSTRACT FROM AUTHOR]

The mode-I and mode-II interlaminar fracture properties of high modulus pitch-based carbon fiber reinforced polymers (CFRPs) (fiber: K13C; resin: EX-1515 cyanate ester) modified with 20–30 nm β-SiC nanoparticles or multiwalled-carbon nanotubes (MWCNTs) were investigated. Different volume fractions of both the β-SiC nanoparticles (1, 2, 5, and 10 vol%) and MWCNTs (1, 3, 5, and 7 vol%) were tested. The values of the mode-I and mode-II interlaminar fracture toughness of the CFRPs containing the lowest volume fractions of these nanostructures were larger compared with the unfilled composite but decreased with increasing the volume fraction of the inclusions. No differences in mechanical properties were observed among the different nanostructure types. [ABSTRACT FROM AUTHOR]