Effect of surface acetylation and grafting of poly(lactic acid) (PLA) on mechanical properties of microfibrillated cellulose (MFC)/PLA all-biomass composite was investigated. As well as the preparation of surface-acetylated or PLA-grafted MFC, grafting of PLA on surface-acetylated MFC was attempted. The introduction of acetyl groups and PLA graft chains on MFC surface was confirmed by FTIR measurements. However, grafting of PLA chains to surface-acetylated MFC (AcMFC) was not successful, possibly because of the lowering of reaction sites on the MFC surface. Young’s modulus and maximum stress of PLA was enhanced by the addition of AcMFC. However, crystallization of PLA was prevented by AcMFC. In contrast, addition of PLA-grafted MFC promoted the crystallization of PLA.
This research focused on effects of lapped length of Kanawatsugi-joint (Japanese traditional timber joint for beam to beam) for compressive properties.E-graded Hinoki(E110 and E90) and Sugi(E90) were shaped Kanawatsugi-joints, and each joint had either lapped length of 240, 300 or 360mm.The followings were found from the result of compressive experiments of Kanawatsugi-joints.1)Splitting, embedment and crush of cells were occurred on Mechi (grooved point) and Komisen-dowel, 2)A lapped part was curved in a direction of perpendicular to the loading axis, 3) Compressive strength of H110(E-graded 110 Hinoki) was 80-100% of design strength and that of H90(E-graded 90 Hinoki) and S90(E-graded 90 Sugi) was 60-70% of design strength, 4)Initial stiffness was 40-60% as large as Young's modulous, 5)The longer lapped length Kanawatsugi-joint had, the smaller compressive strength was on the same grade, 6)The distinct properties was not found between initial stiffness and E-grade,7)Initial stiffness was positively correlated with compressive strength.
A sensory test on uncoated and coated kiri and oak wood was conducted over three seasons (summer, autumn and winter), using the paired comparison method. The subjects (children, young and elderly person) were asked to touch the specimens without seeing. The characteristics of the palms of the subjects, the heat flow from the heated metal disc to specimen, and the coefficient of kinetic friction between the palm and specimen were measured. The density of wood and coating influenced the sensory warmth throughout the above-mentioned seasons. Children and young person were able to determine the sensory sliding more clearly, compared to the elderly, throughout the seasons. The sensory sliding was related to differences in the coefficient of kinetic friction and criteria for determination (“slippery” or “dry”). The children and young person felt comfortable touching the surface of uncoated wood throughout the seasons, to be contributed by the sensory sliding. The comfortable surface in the elderly person was different depending on whether it was summer or winter, because the contributing sense was the sensory warmth.
This study was aimed at evaluating and estimating the shear strength properties of nailed wood (Sugi) connection damaged by decay. Steel and stainless steel nails were driven into specimens, and then the specimens were decayed by compulsion using cultured brown rot fungi (Fomitopsis palustris). The Pilodyn’s penetration depth and the bearing strength were measured to estimate the shear strength of nailed connection damaged by decay. The single shear tests of nailed connection were conducted to investigate relationship between Pilodyn’s penetration depth and shear strength. It was found that the stainless steel nails slightly decreased yield strength with increasing penetration depth. However, the steel nails showed an opposite tendency due to rust. The deeper the penetration depth caused the lower the bearing strength. The shear strength of decayed nailed joint was also compared with the estimated strength by the European Yield Theory (EYT) based on the bearing strength calculated from the penetration depth, and as results of both data showed good agreement. Thus, it was proposed 29 mm of Pilodyn’s penetration depth as the threshold value for nailed connection using Sugi.
The feasibility of porosity calculate by using X-ray computed tomography (X-ray CT) to evaluate the relationship between the cavities in wood attacked by drywood termite of Incisitermes minor and residual bending strength was investigated. Fifty three wood specimens of Japanese cedar Sugi (Cryptomeria japonica) with 1200mm-length attacked by I. minor were prepared for the measurements of density, dynamic longitudinal elastic modulus, ultrasonic velocity, porosity by using X-ray CT, and bending strength. It was related to high positive correlation between density or dynamic longitudinal elastic modulus, and bending strength. It was seemed that the higher negative correlation between the porosity of center part of 360mm of specimen and bending strength, than the porosity of specimen with 1200mm-length. It was possible to select the specimens more than the standard strength of Sugi with the highest accuracy in the relationship between the dynamic longitudinal elastic modulus and the bending strength, by using the ratio of section modulus calculated from the maximum porosity in center parts divided into six in the longitudinal direction as sifting all the cavities in the radial direction.
A practical method to detect wood annual ring structure has been limited to the ionizing radiation such as X-ray though the structure is important in determining the dimensional stability and strength of wood. A millimeter wave technique has attracted much attention as a new technique that can detect the annual ring structure. The relation of annual ring structure to the millimeter wave image, however, has been obscure because the wave is diffracted in wood. In this paper, the effect of diffraction on the millimeter wave image was investigated. The transmission images of the MMW transmitted through 2 mm thick quarter-sawn specimens of six wood species were obtained as the distributions of phase shift and attenuation, and they were compared with the density distributions obtained by the X-ray radiography. The phase shift and attenuation distributions did not always match the density distribution. The electromagnetic wave transmission model considering diffraction well explained this mismatch. This indicates that the diffraction affects the millimeter wave transmission image of wood.
Acoustic emission (AE) testing is one of the major nondestructive testing (NDT) techniques, and it can be used as the real-time monitoring method for the purpose of detecting fatigue damages. However, AE testing data for steels during the low-cycle fatigue test is rarely reported. In this study, AE monitoring was conducted during low-cycle fatigue test for austenitic stainless steel with the aim of detecting fatigue damages and identifying the source of AE. A large number of AE were generated through the fatigue test and the AE data were divided into the increscent phase and decrescent phase. When focusing on the centroid frequency of AE, low frequency data had been observed since the crack size became detectable by PT. Those AE occurred in the process of increscent phase which is loading under tensile and unloading under compression and the contact of the crack surfaces were observed at the increscent phase. This means that the low frequency AE were secondary AE which were induced by friction of the crack surfaces. The behavior of crack surfaces was analyzed by FEM. The results showed that contact condition of crack surfaces were different between crack opening and closure, and it was revealed that friction-induced AE was mainly generated at the crack opening process. Therefore, the potential for monitoring low-cycle fatigue crack was demonstrated by focusing on both the friction-induced AE (secondary AE) and primary AE.
Evaluation of the failure under creep deformation is essential in design and life management of high-temperature components constituting power generation plants. Deformation model as well as life evaluation rule plays an important role in such a evaluation and their accuracy needs to be qualified. In order to estimate variation of stress distribution with time due to creep deformation, creep strain equations are required to be used and their accuracy is important for the reliability of the assessment of creep damage. Creep strain equations for ka-SUS410J3 (ASME Grade 122) steel which is widely used in ultra-super critical thermal power plants were developed in this study. Expressions for the primary and the tertiary creep deformations were developed as well as those for the secondary creep deformation with special attentions to the difference between short-term and long-term behavior as well as dependency of the starting point of the tertiary creep phase on temperature and rupture time.