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For this paper, the impact behaviors and the damage state of plain-woven CFRP reinforced by spread tow due to falling weight were evaluated. Stress-Strain responses of the CFRP using spread tows were investigated under drop-weight impact loading at room temperature. Three leveled impact energy was applied to the surface of the specimen in the drop-weight test. The peak load and absorbed energy were then compared with those of a conventional one and the experimental results showed that the peak load and absorbed energy of the developed CFRP were higher. A large amount of energy was absorbed due to the propagation of macro cracks and delaminations near the counter surface in the developed CFRP. When reinforced by spread tow its structure absorbs a large amount of energy after the initial stage of impact damage. The SAI (static strength after impact) and the FAI (fatigue life after impact) were also examined and the tensile test results showed that the static strength retention of the developed CFRP was higher than those of a conventional one. The developed CFRP also has long fatigue life under the tension-tension cyclic load after the impact. It was found that it maintained superior mechanical properties compared to the original, even after the material was damaged due to impact, because critical propagation of the debonding was prevented around the warp of thin cloth. This paper concludes that reinforcing with spread tow is effective for improving the mechanical properties of plain-woven CFRP during and after impact loading.

A new class of bulk nanocrystalline nickel dispersed with nano-scale WO 3 particles has been synthesized by conventional electrodeposition to clarify the effect of the presence of nano-size dispersions on the strength and thermal stability of nanocrystalline structures. It was found that WO 3 particles of an initial size of 0.1 lm, when suspended in an electrolyte, fragmented into smaller nano-size particles, and were embedded into nanocrystalline nickel matrix of an average grain size of 45 nm during deposition. X-ray diffraction and transmission electron microscopy analyses revealed that phase transition of WO 3 particles occurred from an initial monoclinic to a tetragonal structure. The cause-and-effect relation between the fragmentation and the phase transition of WO 3 particles was discussed. Further hardening was confirmed in comparison with nanocrystalline pure nickel, but its increment was less than that predicted by the classical Orowan-type hardening of the particle-dislocation interaction. The discrepancy may be associated with a different dominant deformation mode which operates in a nanocrystalline regime.

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Nanocomposite materials consisting of a nanocrystalline Ni matrix with grain size ranging from 23 to 40 nm, and nano-size SiO2 particles with average particle size of 7 nm, have been produced by pulse electrodeposition. Grain size was controlled by peak current density. It was observed that SiO2 particles precipitated within grain interior by the transmission electron microscopy (TEM). Hardness and tensile strength of nanocomposites with a grain size larger than 35 nm was higher than that of nanocrystalline pure Ni possibly as a consequence of Orowan precipitation hardening. However, hardness of Ni-SiO2 nanocomposites with a grain size smaller than 30 nm was the same as that of nanocrystalline pure Ni. It was considered that the SiO2 particles do not contribute to hardening because deformation occurs by a grain-boundary-mediated mechanism such as grain-boundary sliding.