Flexible Mechanoluminescent SrAl₂O₄:Eu Film with Tracking Performance of CFRP Fracture Phenomena

Non-destructive testing of carbon-fiber-reinforced plastic (CFRP) laminates with bidirectional fiber bundles (twill-weave) using a mechanoluminescence (ML) technique was proposed. The dynamic strain distributions and fracture phenomena of the CFRP laminates in the tensile testing were evaluated by the fabricated ML sensor consisting of SrAl2O4:Eu (SAOE) powder and epoxy resin. The ML images for the ML sensor attached to the CFRP laminates with bidirectional fiber bundles gave a net-like ML intensity distribution similar to the original twill weave pattern. Specifically, it was found that the ML intensity on the longitudinal fiber bundle, which is the same as the tensile direction, is higher than that on the transverse fiber bundle. This indicates that the ML sensor can visualize the load share between fiber bundles in different directions of the CFRP laminate with high spatial resolution. Meanwhile, the ML sensor could also visualize the ultrafast discontinuous fracture process of the CFRP laminates and its stress distribution. The amount of SAOE powder in the ML sensor affects the tracking performance of the crack propagation. A higher SAOE amount leads to a fracture of the ML sensor itself, and a lower SAOE amount leads to poor ML characteristics

Calculation of the moisture diffusion coefficient at the adhesive interface of double cantilever beam specimens by studying the fracture surfaces

Adhesives used in aircrafts degrade because of moisture. To understand the fractures at the adhesive interface, moisture diffusion coefficients must be estimated, which is challenging and has not yet been reported. In this study, we prepared double cantilever beam specimens using an aluminum adherend and epoxy adhesives, immersed them in a hot bath, and observed the resultant fracture surfaces. The distance of moisture penetration at the interface was estimated from the fracture morphology, and the diffusion coefficient for moisture penetration into the adhesive was measured using a bulk immersion test. Both these values were used to determine the moisture diffusion coefficient at the adhesive interface, which was ∼3 times higher than that of the bulk. The relationship between immersion temperature and moisture diffusion coefficient of the adhesive interface adhered to the Arrhenius equation, as same as that of bulk

Development of highly sensitive mechanoluminescent sensor aiming at small strain measurement

This paper was focused on the elasticoluminescence (ELS) characteristics, especially a response to small strain (below 1000 μst), of mechanoluminescence (ML) sensor using strontium aluminate doped with small amount of europium (SrAl2O4:Eu) synthesized by different methods. By using nitrate decomposition method as a synthetic method of SrAl2O4:Eu, the response to small strain of the ML sensor was enhanced in comparison with using a conventional solid-state reaction method. Based on SEM observation and thermoluminescence (ThL) measurement, we proposed a hypothesis that the sensing characteristic of small strain affect the plate-like shape of SrAl2O4:Eu grain and/or shallower carrier trap levels formed by nitrate decomposition method

The Bactericidal Efficacy of a Photocatalytic TiO2 Particle Mixture with Oxidizer against Staphylococcus aureus

By proving the bactericidal effects of a low-concentration titanium dioxide (TiO2) particle mixture against Staphylococcus aureus, we hope to ultimately apply a mixture of this type as part of a clinical treatment regimen. A bacterial suspension of S. aureus 1×105 CFU/ml was added dropwise to a TiO2 particle mixture (19 ppm TiO2) and irradiated by ultraviolet (UV) light. The colony-forming units were counted and the bacterial survival rate was calculated. In the control sample, the bacterial survival rate was 83.3% even after 120 min. In the TiO2 mixture + UV sample, the bacteria count dropped sharply, reaching 17.3% of the baseline value at 30 min and 0.4% at 60 min. TiO2 particles dispersed in water mixtures are known to elicit highly efficient UV absorption and greater bonding to bacteria. A reaction of the TiO2 with another oxidizer altered the aqueous pH and accelerated the photocatalytic chemical reaction. The TiO2 particle mixture showed high antibacterial action against S. aureus even at a low concentration

Photocatalytic bactericidal action of fluorescent light in a titanium dioxide particle mixture: an in vitro study.

Traditional titanium dioxide (TiO(2)) has photocatalytic bactericidal properties only under ultraviolet (UV) irradiation, which restricts its use in clinical treatment regimens. In this study, we evaluated the photocatalytic bactericidal effects of an aqueous system of TiO(2) particles irradiated by fluorescent light (FL) on Staphylococcus aureus. A TiO(2) particle mixture containing 19 ppm (0.019 mg/mL) of TiO(2) was prepared. A bacterial solution of 1 x 10(5) CFU/mL was added one drop at a time to the TiO(2) mixture. The resulting product was then irradiated with FL. The bacterial survival rate decreased steadily in the TiO(2) mixture group, reaching 76.7% after 30 min of FL irradiation and 10.9% after 60 min. After 60 to 180 min, the bacterial survival ratio of the TiO(2) mixture group was significantly lower than that of the control group (P < 0.05). The present study indicates that treating the surfaces of surgical devices and the surgical field with a TiO(2) particle mixture can create a nearly sterile environment that can be maintained throughout surgery, even at low luminous intensities

Photocatalytic TiO2 particles confer superior antibacterial effects in a nutrition-rich environment: an in vitro study

Titanium dioxide (TiO2) is known to confer photocatalytic bactericidal effects under ultraviolet (UV) irradiation. Few reports are available, however, on the clinical applications of TiO2 particle mixtures. Our objective in the present research was to evaluate the in vitro bactericidal effects of a TiO2 particle mixture in a nutrition-rich biological environment. A bacterial suspension of Staph-ylococcus aureus and epidermidis 3 × 103CFU/mL was added to a TiO2 particle mixture (0.038 mg/mL) containing mainly sodium percarbonate and citric acid. To simulate a biological environment, 40 μL of 10% bovine serum albumin was added and the culture temperature was maintained at 37°C. The resulting product was irradiated by UV light and the bacterial survival rate was calculated for each time of UV irradiation. In the control sample treated with distilled water + UV, the bacteria survived at a high rate even after 180 min. In the TiO2 mixture+ UV sample, meanwhile, the bacterial survival rate dropped to 43.8% and 6.0% of the baseline values in S. aureus and S. epidermidis, respectively, after 60 min of UV irradiation. The photocatalytic antibacterial action of the TiO2 particle mixture was high even in a protein-rich biological environment