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この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。

この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。

この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。

In order to predict the service life of plywood heating floors, dry-heat exposure test of lauan plywood made with each of six type of typical wood adhesives was carried out at 50°, 70°, 100° and 150℃ for 250 days. Internal bond strength and location of failure of the exposed specimens were measured at selected intervals. Data were plotted as a function of the exposed time. Confidence limit was applied on the regression and the service life was calculated by extraporating the lower confidence limit curve to the half-strength. The apparent mechanism of dry-heat degradation of plywood in 150° and 100℃ seemed to differ from the lower temperature exposures. On 70° and 50℃, more conservative estimation was made by the kinetic method on the Arrhenius relationship. The result showed the detrimental effect of the acid catalyst on polyvinyl-acetate cross-linked and urea resin adhesives. Plywood specimens produced with melamine, phenol, phenol-resorcinol, and resorcinol resin adhesives showed excellent durability in dry-heat exposure at temperature normally found in service of floor heating., この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。

In order to obtain basic design data of wood butt joints with metal plate connectors, static tensile tests were made on the joints connected with sixteen types of plate. Two types of failure mode of joints were observed. In the case when joints failed in withdrawal of the teeth, a linear relationship between ultimate load of joints and specific gravity of wood existed, and strength per tooth increased by about 12 kg with increasing specific gravity by 0.1. In the case when joints failed in tension at the middle of the plate, ultimate load of joints did not depend on the specific gravity of wood but on tensile strength of the plate connector, and strength per tooth decreased with increasing the number of row of the teeth. Transition of these two types of failure mode was found on six rows type of the plate; withdrawal of teeth was observed when the number of row was less than six., この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。

A simple shear creep test machine was proposed and creep test was made with ASTM standard shape specimens. Also comparative measuring method of shear deformation was discussed. The results obtained were as follows: 1) The test machine made as a prototype for tensile shear creep test was capable to transmit more than 1,300 kgf to the specimens so it would be suitable for test about 69% of shear strength (P_=1,896 kgf), 2) The measuring method of shear deformation, which had the measurement points mounted on brass tips placed on loading plates edge, can be considered practical. Although the glue-line deformation between specimen and loading plates tested have been neglected. Prototype with accuracy and lower costs was achieved. Therefore, it is possible to extend the creep test period or to make simultaneous tests on many specimens when constructing several test machine., この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。

Fracture Toughness G_c of Wood-Epoxy adhesive system under external shear force was evaluated by employing the experimental compliance method based on the Griffith-Irwin fracture theory. Invariability of G_c with the different glue line length was tolerably recognized and the representative value of G_c for the above system was about 0.25 (cm・kg/cm^2) throughout the series of glue line thickness tested. Fracture mode and stress distribution were discussed with some helps of Finite Element Method., この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。

The paper concerns with effect of the mechanical properties of glue-line on the cleavage fracture toughness of wood-epoxy resin bond systems. Tensile stress-strain relations of the resin films flexibilized with polysulfide in various grades were tested at a range of head speed 0.09 mm/min to 180 mm/min and temperature 20℃ to 60℃. Resins containing 20 to 40 parts per hundred of resin (phr) behaved like elasto-plastic material and that of 60 phr like rubber. Numerical analysis of stress distribution in cleavage fracture toughness test specimens of wood-flexibilized epoxy resin bond system was made by using the values of mechanical properties of resin films obtained above. Less stress concentration was found on the tip of a crack in thicker and more flexible glue-line. Higher stress concentration was found on thinner and more rigid glue-line arid on lower density adherend. Test results on cleavage fracture toughness G_ of wood-epoxy resin bond specimens showed clearly that increasing flexibility and thickness of glue-line could effectively improve cleavage fracture toughness of wood-glue bond system., この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。

Strain energy release rate G_I of DCB-FTAL (Double Cantilever Beam with Finite Thickness of Adhesive Layer) specimen was determined so as to include some variables as thickness and flexibility of adhesive layer and sizes and mechanical properties of adherend. For sharp crack case, the derived equation of GI was compared with previous results, on the other hand, in case of thick adhesive layer, the derived equation of compliance C was compared with experimental results. Fracture Toughness G_ of DCB-FTAL specimen (Buna-Epoxy, EP-60 system) was also determined, and obtained results were discussed together with previous results., この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。

Low-density particleboards bonded with an isocyanate compound adhesive were produced in a full-scale size and their physical properties were examined. The density of the raw materials (Shorea spp.) was 0.4 g/cm^3 and those of the boards 0.3-0.5 g/cm^3. Therefore, the compaction ratios of the boards were in the range of 0.75-1.25. The results obtained are as follows; 1) Bending strength in dry condition of boards with air-dry density 0.4 g/cm^3 was 100 kg/cm^2 which is higher than that of Type 100 particleboard denned by JIS A-5908. This can be much improved by overlaying veneers on the particleboard. 2) Internal bond strength of boards was relatively high, in spite of the low compaction ratios. 3) High dimensional stability both in the plane and in the thickness directions of board was obtained on account of the low compaction ratio and the high water resistivity of the adhesive., この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。

Flakeboards in the density range of 0.4-0.65 g/cm^3 were produced using Albizia falcata as raw material and a urea formaldehyde resin, a phenol-melamine formaldehyde resin, and an isocyanate compound as adhesives. Mechanical properties and dimen sional stability of boards were determined. Using long flakes from this low-density species, high MOE and MOR was obtained in relatively low-density board. Further improvements in internal bond strength and the dimensional stability in thickness direction may enable to produce boards sufficient for structural use. Isocyanate bonded board showed superior properties to those bonded with other adhesives., この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。

Stress analysis by finite element method of tensile shear test specimens of steel-balsa-steel sandwich panel for creep test was made statically. The stress distribution of five different shapes of sandwich panel specimens, two of them in accordance with ASTM-C-273, were analysed through the calculation of normal stress (σ_Y), maximum principal stress (σ_1), shear stress (τ_XY) and principal shear stress (τ_max). The presence of stress singularities at the reentrant corners made by specimen and loading plates suggests fracture occurance in balsa core near the corner. Stress intensity factors (KA) in balsa core near the corner were calculated under assumption of similarity with that in homogeneous body. The results obtained were as follows: 1) σ_Y, σ_1 and τ_max of balsa core concentrated near the reentrant corners, and τ_XY distribution was uniform throughout the balsa core, 2) Comparing K_A of various specimens it was suggested that the estimated fracture load on specimens shaped within the range specified by ASTM standard (length l/thickness t≧12) did not vary. Fracture load of specimens with l/t=8.2, 6.3 and 4.2 were lower than those of the standard specimens. Therefore, the standard shape will be utilized in the further investigation: tensile shear creep test of sandwich panel as floor deck (II)., この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。

Nine wood quality indicators are compared with three groups of growth rates and three types of load-deflection curves in bending on 36 cultivars of juvenile Japanese cedar (Cryptomeria japonica D. Don). The fast-grown trees have shorter tracheids. In the load-deflection type having the large plastic region, tracheid length is shorter and fibrils lie more flatly and bending modulus of elasticity is lower on the same specific gravity as in other two load-deflection types. The trees in this type, therefore, seem to be more juvenile. Moreover, much proportion of the trees in this type belongs to the fast-grown group. Then, by all meams, the precise information of wood quality is necessary for the utilization of fast-grown cultivars., この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。