Masahiro Yoshinobu

Effects of fiber length and orientation on elasticity of fiber-reinforced plywood

Short carbon fibers, a reinforced material in wood veneer composites, were used to investigate the effects of fiber length and orientation of fibers on the elasticity of plywood. The technical feasibility, elasticity, and strength of the reinforced plywood with short carbon fiber were evaluated. In a short fiber reinforcement system, the fiber length does not directly influence the reinforcement in Coxs theory when the fiber length exceeded a certain length. When the length of short carbon fiber is beyond 3 mm, the high reinforced result was obtained in the experiment. However, if fiber length was too long, the reinforced result was less owing to the bridge between fibers and the increase of holes. The optimum fiber length must be considered. The orientation of fibers has a strong influence on the reinforcement. Unidirectional, perpendicular, and random orientation displayed different influence on the elasticity. Experimental results were discussed with Coxs method. Reinforced plywood with short carbon fibers in random orientation has a higher shear modulus and bending strength than the controls, in addition to other mechanical properties.

Young’s modulus and shear modulus of solid wood measured by the flexural vibration test of specimens with large height/length ratios

Abstract The Young’s modulus (modulus of elasticity, MOE) in the longitudinal (L) and radial (R) directions and the shear modulus (SM) in the LR plane of Douglas fir were determined by the flexural vibration (FV) tests under the free-free condition based on Timoshenko’s vibration equation. In the tests, the height/length (H/L) ratio was varied from 0.05 to 0.3. In addition, the test data were analyzed numerically and the effectiveness of Timoshenko’s equation was examined. The MOE and SM were calculated based on the rigorous and approximated solutions of Timoshenko’s equation. The inaccuracy of the approximated solution was enhanced when the H/L ratio of the specimen was too large. In contrast, the rigorous solution enabled the accurate calculation of these moduli in a wider range of length/depth ratios than the approximated solution.

Effects of helical angle of router bit on acoustic emission

The purpose of this study was to investigate the effects of changes in the helical angle of the router bit on the acoustic emission (AE) signal for various workpiece grain angles. The helical angle varied from 0° to 50° at 10° increments. The workpiece grains were oriented from 0 degrees (cutting parallel to the grain), through 90° (cutting end of the grain), to 165° at 15° increments. The AE signals and machined surface roughness were measured in an attempt to clarify the relations between them. The results were summarized as follows: (1) The AE signals were lowest in the “with the grain” cutting zones and slightly increased in the “against the grain” cutting zones; they rapidly reached the highest values at the 135°–165° grain angles. The greater the helical angle of the router bit, the smaller were the AE count rates for each grain angle investigated. There was no significant change in AE generation for helical angles of 0° and 10°. Moreover, the greater the feed rate, the greater was the AE count rate for every cutting condition investigated. (2) The surface roughness, similar to the AE count rate, had the lowest values in the “with the grain” cutting zones, slightly increased until the 120° grain angle, and then rapidly become extremely rough, reaching a maximum at the grain angles of 135°–150°. There was no remarkable change in the machined surface roughness while routing “with the grain” using the router bit of greater helical angle. However, when routing “against the grain,” the greater the helical angle the smoother was the machined surface. (3) There were correlations between the AE count rate and the machined surface roughness for each helical angle investigated. Therefore, acoustic emission has shown promise for monitoring and controlling the routing operation, including various grain angles and helical angles of the router bit.

Damage of PVD-Coated Cutting Tools Due to Interrupted Cutting of Ni-Based Superalloys

Ni-based superalloys are typically difficult-to-cut materials. During machining, the cutting forces and temperatures of these superalloys are generally higher than those of other materials. Therefore, the tool life of the coated carbide cutting tools used for superalloy machining is shortened. This study evaluates the damage of the coated end mills during interrupted cutting of alloy 718 and finds the coating properties necessary for improved cutting of Ni-based superalloys. Damage of the PVD-TiN-coated cutting tools was observed by scanning electron microscopy and transmission electron microscopy of the surfaces and cross sections. In addition, friction forces were measured during turning for some coatings, and hardness of the coatings was measured after annealing. Plastic deformation of the coating and crack formation was shown to occur at the coating cross section. In addition, we determined that the major factor for the damage was high friction force between the coating surface and work material at high temperatures. In summary, coatings with stability at high temperatures and low friction forces during machining can reduce the damage of coated cutting tools, thus increasing the tool life.

Effects of specimen configuration and measurement method of strain on the characterization of tensile properties of paper

Uniaxial-tension tests of copy paper were conducted to measure the tensile properties, including Young’s modulus, proportional limit stress, and tensile strength in the machine direction (MD) and cross direction (CD) using straight and dog-bone-shaped specimens. In the tests using the straight specimen, the distance between the grips was varied. Additionally, the tensile strain was obtained from the crosshead movement and elongation between the lines photographed by a CCD camera. When using a straight specimen in the MD, the grip distance influenced the Young’s modulus value, and the tensile strength was markedly lower than that of the dog-bone-shaped specimen. In contrast, the tensile properties in the CD could be obtained even when using the straight specimen while reducing the influence of stress concentration at the grip.

In-plane shear strength of paper measured by asymmetric four-point bending test

Abstract The in-plane shear strengths (IPSS) of copy paper, filter paper, and sack paper were obtained from an asymmetric four-point bending (AFPB) test. Rectangular tabs of medium-density fibreboard (MDF) were bonded to the paper specimen. The length of the clearance between the tabs was varied, and the influence of the clearance on the IPSS value was investigated. The IPSS obtained from the AFPB test was compared with that obtained from a 35° off-axis tension (OAT) test, which was proposed in a previous study. The IPSS values obtained from the AFPB tests on the copy paper and sack paper were significantly lower than those obtained from the 35° OAT tests because of the localised buckling caused by the negative principal stress. In contrast, the IPSS values obtained from the AFPB and OAT tests on the filter paper were in agreement when the clearance length was >5 mm because the buckling effect was excluded.

Treatment of fast-growing poplar with monomers using in situ polymerization. Part I: Dimensional stability and resistance to biodegradation

Fast-growing poplar (Populus Xeuramericana NL-95) has been extensively cultivated in China. However, because of its poor quality, poplar wood is commonly used only in the manufacture of low-grade wood products. If the wood could be improved by postharvest treatment, it would be more useful and more saleable. Such modification is possible. Our team has developed a protocol to modify fast-growing poplar by impregnating poplar wood with styrene (ST) and glycidyl methacrylate (GMA); this treatment is followed by in situ polymerization by means of thermal treatment. Experimental results show that the treated wood absorbed only one-fifth of the water absorbed by untreated wood when both were submerged in water for 1 week. The treated wood was also two times as dimensionally stable. When treated and untreated wood specimens were exposed to termites and to the fungi that cause dry rot, the treated wood was 9.3 times as resistant to termites and 3.8 times as resistant to fungi. Specimens of treated wood were examined using Fourier transform infrared spectroscopy, which showed that a grafting reaction and copolymerization had occurred, bonding the hydroxyl groups of the wood cell walls to the GMA and ST. Scanning electron microscope observation of the treated wood showed that the cell lumens had been filled with polymers and that the interfaces between wood cell walls and polymer were hard to distinguish.

Evaluation of rolling shear strength of plywood by flexural vibration method

The rolling shear strength of plywood was evaluated using a flexural vibration test. Test specimens were lauan and Douglas fir three-ply plywoods made from thick veneers. The dynamic shear and Youngs moduli were determined using the flexural vibration method, which involved in-plane and out-of-plane flexural vibration. The rolling shear strength was determined using the static destructive method, which is dependent on the direction of the lathe check in the core veneer. Before and after accelerated aging treatments were conducted, there were relations between out-of-plane dynamic properties (out-of-plane shear and Youngs moduli) and its rolling shear strength. It was concluded that the rolling shear strength is related not only to the shear property of the core but the flexural stiffness of two faces when the deformation of out-of-plane plywood was not restrained.

Off-axis tensile strength and evaluation of the in-plane shear strength of paper

Abstract The off-axis tensile strength (OATS) of copy paper, filter paper, and sack paper was obtained from dog-bone specimens. The relationship between OATS and the off-axis angle (OAA) was predicted under several failure conditions. Additionally, the shear strengths (SS) of these papers were evaluated based on the results of OAT tests. The OATS could be accurately predicted under several Hill-type failure conditions. An equation for deriving the in-plane SS of these papers was proposed based on the tensile strength of the specimen with a 35° OAA, in which the contribution of the shear stress component was maximum.