In this study, the influence of pantyhose (PS) color in beige-colored PS on the visually perceived PS surface roughness, as well as the resultant evaluation index, were examined. In addition, sensory evaluation and relevant statistical analyses of the visually perceived PS surface roughness were performed for a leg model with various beige-colored PS among Japanese females. However, the stitch density of the extended PS fabric on a leg model was the same across all PS samples. Moreover, the relationship between the visually perceived pantyhose surface roughness, the fabric color, and the visual features obtained via image analysis of the PS-covered leg model, were investigated. Although the physical surface roughnesses were the same, the obtained results confirmed the influence of the PS color on the visually perceived PS surface roughness. Additionally, the lightness (L* value) of PS color was proved to be useful as an evaluation index for the visually perceived PS surface roughness.

The purpose of this study is to design a hybrid CFRP structure using pitch-based carbon fiber and PAN-based carbon fiber, and to develop an optimal hybrid CFRP structure. Various cross-laminated hybrid CFRP structures were fabricated, and the composition and arrangement of pitch-based and PAN-based carbon fibers were changed. The developed CFRP structures were investigated by bending and impact measurements. As a result, the following findings were obtained.
The results of the mechanical properties of three-point bending showed that it was possible to obtain higher bending strength than the individual pitch-based or PAN-based CFRP structure by hybridizing. The hybrid CFRP structure with 20% pitch-based carbon fiber in the outermost layer and 80% PAN-based carbon fiber in the core layer shows higher flexural strength, flexure and fracture initiation energy than PAN-based 100% CFRP. It was confirmed that the reinforcement effect of the hybrid of pitch type and PAN type CFRP was remarkable with the synergistic effect of both carbon fibers.
From the dynamic mechanical properties by the impact test, a hybrid CFRP structural material with PAN-based carbon fiber 60% in the outermost layer and pitch-based carbon fiber 40% in the core layer, the residual strength after maximum load and the total absorbed energy are greatly improved. Ultrasonic testing shows that pitch-based carbon fibers are arranged in the outermost layer, which reduces delamination and improves internal damage resistance, and supports the hybrid reinforcing effect of pitch-based and PAN-based CFRP. All of these results indicated it is possible to improve the static and dynamic mechanical performance and optimize the material structure by designing the ratio of the pitch-based carbon fiber and the PAN-based carbon fiber and the arrangement in the thickness direction of CFRP structures, which may help in the future CFRP structural design.

Regenerated cellulose fibers were prepared by dry-jet wet spinning of cellulose solutions using three different solvents: the ionic liquids 1-butyl-3-methylimidazolium chloride (BMIMCl) and 1-ethyl-3- methylimidazolium diethyl phosphate (EMIMDEP), and the solvent used in the lyocell process, N-methylmorpholine N-oxide monohydrate (NMMO·H₂O). The mechanical properties and fibrillation tendencies of fibers prepared under the same spinning conditions were compared. The results showed that fibers generated using BMIMCl exhibited the highest tensile and knot strengths, and the highest fibrillation resistance, followed by fibers spun using EMIMDEP and NMMO·H₂O. Structural analyses by wide angle X-ray diffraction and polarizing microscopy revealed that the high total molecular orientation of fibers spun from BMIMCl solution contributed to their high tensile strength and Youngʼs modulus. We observed the coagulation behavior in water of each cellulose solution and found that the coagulated cellulose gels were transparent using BMIMCl, translucent using EMIMDEP, and opaque using NMMO·H₂O. These differences in appearance are due to different void structures formed in the regenerated cellulose depending on the solvent. For BMIMCl, the transparency of the cellulose gel indicated a dense inner structure, resulting in high knot strength and good fibrillation resistance of the fibers. In contrast, the opaque appearance of cellulose gel regenerated from NMMO·H₂O solution is due to the presence of coarse voids, in turn closely related to the lower knot strength and fibrillation resistance of the fibers. The results indicate that BMIMCl is the best of the three tested solvents for preparing high performance regenerated cellulose fiber.

In order to comprehensively investigate from the effects of the morphology (length and entanglement) of the molecular chain on the strength of polyethylene to its fracture mechanism, molecular dynamics simulation of uniaxial tension using low molecular weight amorphous polyethylene and firstprinciples calculation of uniaxial tension using methylene trimer were performed. As a result, it was found that when the molecular weight is twice the entanglement molecular weight, the molecular chains can not form a network structure. And the bond stretch had the greatest effect on stress, in contrast, the van der Waals force had negative effect on stress and the effect was larger at lower molecular weights. In addition, it is also found that the decrease in stress after reaching the maximum stress is due to slipping of the molecular chains because the molecular chains donʼt break due to tension. Furthermore, the maximum stress increased with the longer the molecular chain because the entanglement point acted as a resistive force against the tension and because the longer the molecular chain, the higher the number of entanglement points. From the above results,it was clarified that the entanglement works positively for stress, the van der Waals force works negatively,and the entanglement of the molecular chains has a large effect on the strength of polyethylene.