A new method to install carbon nanotubes（CNTs）as a secondary reinforcement at the fiber-matrix interphase in carbon fiber reinforced plastics（CFRPs）has been developed. This new approach delivers CNTs by coating carbon fibers（CFs）with CNTs which are subsequently impregnated with an epoxy resin. In this method, a cationic polymer treatment of the CNTs was used to create a stable dispersion of the CNTs in water, achieving a uniform coating of CNTs to the fiber surface. Using the CNT-coated CF and untreated CF as a control, unidirectional CF/epoxy composites were fabricated using a prepregging method. Then, the CFRP’s mechanical and electrical properties were evaluated. The results show that the compressive, interlaminar shear strengths and Mode I interlaminar fracture toughness were improved from the control by 22％, 11％ and 48％ respectively with only 0.39 wt ％ CNTs. The electrical conductivities in both the 90° and through thickness directions were improved by two to three orders of magnitude. The SEM and TEM observations of the composites revealed that the CNT/epoxy resin layer of 100-200 nm thickness was formed at the fibermatrix interphase. These results indicate the importance of designing the fiber-matrix interphase to improve the mechanical and electrical properties of fiber reinforced polymer composites.

The main factor of strain-induced crystallization（SIC）in cross-linked natural rubber（NR）has been believed to be the entropy change due to the stretching of molecular chains. However, the experimental results were inconsistent with this idea. The author reexamined the equilibrium melting temperature of NR crystal and found it to be ca. 61 ℃ which is considerably higher than the believed value of 35 ℃. Energy barrier for the formation of chain-folded nuclei was calculated to be two orders of magnitude higher than kT（k: Boltzman’s constant, T: absolute temperature），indicating that spontaneous nucleation is quite slow. The melting behavior of strain-induced NR crystals was inconsistent with the chain-folded crystals. Considering these results, the author proposed that the main factor to induce crystallization is the formation of bundle nuclei due to chain orientation. Furthermore, considering the melting behavior of so-called shape memory NR, the melting temperature of strain-induced NR crystals was found to be suppressed by the contracting force of surrounding amorphous chains. In this way, the characteristic feature of SIC can be explained.