Strain energy density functions are used in CAE analysis of hyperelastic materials such as rubber and elastomers. This function can originally be obtained only by experiments using biaxial deformation, but the difficulty of such experiments has made it almost impossible to put the function to practical use. Furthermore, it has been unclear how to introduce the strain energy density function necessary for CAE analysis from the results of biaxial deformation experiments on rubber. In this study, parameters of the Ogden and Mooney–Rivlin approximations of the strain energy density function were derived from the results of biaxial deformation experiments on silicone rubber, and their validity was verified. These results showed that it is best to determine the coefficients of the approximate equations for the strain energy density function after 10 cycles of repeated elongation of rubber in an equal biaxial deformation state, followed by equal biaxial elongation, uniaxial constrained biaxial elongation, and uniaxial elongation to obtain these three stress–strain curves.

Commingled yarns consisting of thermoplastic nylon fibers and carbon fibers can be used to produce superior carbon fiber reinforced thermoplastics (CFRTP) by applying fiber spreading technology after commingling. In this study, we examined whether spread commingled carbon fiber/nylon fiber yarns could reduce the impregnation distance, as there are few reports on this. From this study, the following are revealed. The impregnation speed of the nylon resin on the carbon fiber was very fast, less than 1 min. As the molding time increased, the tensile strength and tensile fracture strain slightly decreased, and the nylon resin deteriorated. The effects of molding time on flexural strength, flexural modulus, and flexural fracture strain were negligible. From the cross-sectional observation conducted to confirm the impregnation state of the matrix resin, no voids were observed in the molded products, regardless of molding time or molding pressure, indicating that resin impregnation into the carbon fiber bundle of the spread commingled yarn fabric was completed at a molding pressure of 5 MPa and a molding time of 5 min.

An investigation into the acute toxicity of mechanically fibrillated cellulose nanofibers (fib-CNFs), with a fiber length ranging from 500 to 600 nm, was conducted in accordance with the OECD TG412 guidelines. In this study, rats were exposed to fib-CNFs via nasal inhalation for 6 h daily over a 28-day period. The highest exposure concentration was set at 35 mg/m³, with intermediate and low concentrations at 7.0 mg/m³ and 1.5 mg/m³, respectively. No significant differences were observed in body weight, hematological parameters, or biochemical profiles between the fib-CNF-exposed groups and the control group. However, the histopathological examination of lung tissue revealed elevated macrophage counts in both the alveolar spaces and lymph nodes, accompanied by a significant increase in lung weight. The most severe effects were observed in the high-concentration group, while the low-concentration group exhibited only mild inflammatory changes. Based on these findings, the no observable adverse effect level (NOAEL) for the acute toxicity of fib-CNFs is estimated to be below 1.5 mg/m³.

Mechanically fibrillated cellulose nanofibers, known as fib-CNF (fiber length: 500 nm; diameter: 45 nm), are used in composites and as a natural thickener in foods. To evaluate their safety, we conducted a 28-day study in mice with inhalation exposure at 0.2 mg/body and oral administration of 400 mg/kg/day. Inhalation exposure to fib-CNF caused transient weight loss, changes in blood cell counts, and increased lung weights. These changes were attributed to adaptive responses. The oral administration of fib-CNF for 28 days resulted in no apparent toxic effects except for a slight decrease in platelet counts. The fib-CNF administration using the protocols studied appears to be safe in mice.

The impact of oral administration of mechanically fibrillated cellulose nanofibers (fib-CNF), a commonly used nanofiber, on toxicity and health remains unclear, despite reports of the safety and beneficial effects of chitin-based nanofibers. Thus, evaluating the oral toxicity of fib-CNF in accordance with OECD Test Guideline 407 (TG407) is essential. This study aimed to assess the safety of orally administered fib-CNF through an acute toxicity study in rats, following the OECD TG407 guidelines for 4 weeks. CNF “BiNFi-s” FMa-10005, derived from mechanically fibrillated pulp cellulose, was administered via gavage to male and female Crl:CD(SD) rats at doses of 50, 150, 500, and 1000 mg/kg/day for 28 days, with a control group receiving water for injection. The study evaluated the toxic effects of repeated administration, and the rats were monitored for an additional 14 days post-administration to assess recovery from any toxic effects. The results showed no mortality in either sex during the administration period, and no toxicological effects related to the test substance were observed in various assessments, including general condition and behavioral function observations, urinalysis, hematological examination, blood biochemical examination, necropsy findings, organ weights, and histopathological examination. Notably, only female rats treated with 1000 mg/kg/day of CNF exhibited a consistent reduction in body weight during the 14-day recovery period after the end of treatment. They also showed a slight decrease in pituitary and liver weights. However, hematological and blood biochemical tests did not reveal significant differences, suggesting a potential weight-suppressive effect of CNF ingestion.

When nanofibers are used for filters, their water resistance is important. We tried to realize the water resistance of nanofibers with ethylene-vinylalcohol copolymer (EVOH) made from aqueous solvent. We also investigated the incorporation of polyurethane (PU) emulsion dispersed in water to improve the adhesion between the nanofibers and the nonwoven fabric of the substrate, and to improve rubber elasticity to the nanofibers themselves. There are few reports on research to produce nanofibers by electrospinning method by combining these two techniques to make the solvent as water as possible. It was possible to realize the nanofiber production of EVOH in a state close to the aqueous system which was difficult up to now by combining with PU. Since PU is excellent in adhesion and firmly adheres to the nonwoven fabric of the base material, peeling of the nanofibers from the base material does not occur, and excellent PM 2.5 particle removal is possible even with very small nanofiber basis weight. Furthermore, it was found that nanofibers can be produced even by using a coil type electrospinning apparatus for industrialization. In the future, to reduce the solution concentration of PU / EVOH to 10 wt%, it is necessary to devise measures such as increasing the hydrophilic component in the structure of PU.