The main factors that contribute to the adhesive strength at the fiber/matrix interface of fiber reinforced thermoplastics (FRTP) are considered to be the chemical and physical bonding between the fibers and matrix resins. The chemical and physical bonds have not been evaluated separately, and the effect of each bond to the mechanical properties of FRTP has not been clarified. In this study, by using glass fibers with a sizing agent and glass fibers in which the sizing agent was removed and chemical bonding was deliberately not applied, we measured the fiber/matrix interfacial shear strength with several polyamide resins of different densities and terminal group concentrations by the microdroplet test. Thereby, the effects of physical and chemical bonding on the fiber/matrix interfacial shear strength were clarified. The mechanical properties of FRTP were also evaluated to clarify the effects of the chemical and physical bonding. The contribution of physical bonding was larger than that of chemical bonding in the fiber/matrix interfacial shear strength. The contribution of physical bonding was positively correlated with the density of resins, meanwhile the contribution of chemical bonding resulting from the application of the sizing agent was positively correlated with the terminal group concentration of resins. The interlaminar shear strength and bending strength of FRTP were positively correlated with the fiber/matrix interfacial shear strength regardless of the application of sizing agent to the glass cloth used to FRTP. These interlaminar shear strength and bending strength of FRTP using glass cloth with sizing agent were higher than that without sizing agent. This result indicates that the contribution of chemical bonding to the interlaminar shear strength and bending strength is different from the fiber/matrix interfacial shear strength and larger than that of physical bonding.

In order to evaluate residual creep life of ASME Grade 91 weldment, Phased Array Ultrasonic Testing (PAUT), High Temperature Superconductor - direct current - Superconducting Quantum Interference Device (ECT・HTS-dc-SQUID), observation of replica and hardness measurement were used to detect creep damages for creep interrupted specimens. It was clarified that the threshold of the creep damage that PAUT and ECT・HTS-dc-SQUID could detect appear in later stage of creep deformation. Creep voids were detected on the replica obtained from surface of creep specimens just before creep rupture. Capacitive strain sensor, laser displacement meter and SPICA strain measurement were tried to detect creep strain. Creep curves by the capacitive strain sensor and laser displacement meter were similar with that of conventional extensometer with a linear gauge. Strain measured by SPICA in heat affected zone monotonously increased during creep. Strain measured by capacitive strain sensor, laser displacement meter and SPICA and damage detected by PAUT and ECT・HTS-dc-SQUID were assumed to be useful for residual creep life assessment.

In the same materials, film and bulk materials show different mechanical properties. Slip and crack initiation is rare in steel thin films. The slip that does occur is also dependent on the influence of the pearlite volume ratio and the film thickness directional constraint. The slip is reported to have an in-plane shear component and an out-plane shear component. Therefore, in this study we conducted fatigue tests under in-plane pure shear loading on specimens with steel films pasted to acrylic bar. As a result, two types of slips were observed: wavy slip and single linear slip and more wavy slip occurred in pure iron and S10C, while more single linear slip occurred in S45C. Crack initiation ratio and single linear slip initiation ratio showed similar increasing behavior. In addition, wavy slips in the grain were found to be in the out-plane direction, and a single linear slip in the grain was in the in-plane direction. Wavy slip (out-plane slip) is considered to occur only in ferrite that deformation is restrained by grains existing in the thickness direction. Single linear slip (in-plane slip) is considered to be caused by concentrated slip deformation or separation of slip planes in ferrite where plastic deformation is inhibited by hard pearlite, resulting in cracks.

The effect of hybrid surface treatment composed of plasma nitriding and various DLC (diamond-like carbon) coatings on the tribological properties, the mechanical properties and the fatigue properties of austenitic stainless steel SUS316 was comprehensively investigated. In this hybrid surface treatment, plasma nitriding was made as a pre-treatment and then the following three kinds of DLC films were coated by UBMS (unbalanced magnetron spattering) method: a regular DLC film, a silicon-doped DLC (Si-DLC) film and a titanium-doped DLC (Ti-DLC) film, respectively. As the test temperature was increased, the change to the graphite structure with high solid-lubricity was promoted, so the friction coefficients of all DLC-coated materials were reduced. The friction coefficient of the Si-DLC material was the lowest at room temperature, but it became comparable to that of the regular DLC material when the test temperature was beyond 373 K. The Ti-DLC material had a higher friction coefficient than the other two DLC-coated materials without depending on the test temperature. Since the microstructure of the substrate was not influenced by plasma nitriding and each DLC coating, there was no marked change in the mechanical properties with them. The hardened layer formed by plasma nitriding effectively suppressed the initiation of fatigue cracks from the surface and markedly improved the fatigue strength. Also in all DLC-coated materials, since the hardened layers formed under the DLC films suppressed the initiation of fatigue cracks, their fatigue strengths reached the same level as that of the plasma-nitrided material.

There is a method using a strain gauge as a dynamic measurement of micro-fatigue cracks. However, it is not always effective in term of measuring micro-fatigue cracks due to direct adhesion with the object and durability issues. Therefore, we focused on the inverse magnetostrictive effect, which is a magnetic effect of ferromagnetic materials, and measured the change of the magnetic field by a simple instrument without adhesion with glue. It is possible to measure micro fatigue crack information.In this study, the change of magnetic field around specimens caused by the inverse magnetostrictive effect was obtained and analyzed using a coil and a hall sensor. Based on a certain coil output, the coil output was estimated from the relationship between the strain rate and the coil output.

High-strength joints used in timber structures are increasing to utilize the shear properties of wood. Thus, it is important to understand the long-term shear performance. Therefore, we proposed the tensile shear testing method to investigate the long-term shear performance of wood. This testing method is to apply stabilized axial load for a long-term and to be able to measure the shear deformation. In order to evaluate the method, the results were compared with results of JIS block shear test. As a result, the mean value of shear strength in the proposed method was 30% lower than the block shear test. The reason for the small results of the proposed method is that the specimen has two shear face and breaks at the weak side, and the shear face is affected by rotation due to the tensile deformation of the perpendicular to grain direction. Therefore, the coefficient of variation of 6.8% in the proposed method shows smaller than 11.1% in the block shear test. And the shear strength value of the proposed method was little bit higher than one of the four-point-bending type shear test methods, and all specimens were shown the shear failure. Based on these results, the proposed method was judged to be useful as a shear test method.

In order to realize transparent and hygroscopic films, it was shown that transparent hygroscopic films could be realized by surface modification of 4A zeolite with a median diameter of 50 nm to bring the refractive indices of the EVA resin and zeolite closer together. In order to make this technology applicable to general purpose, LDPE or LLDPE is suited as the base resin, and thin films should be produced by the inflation method. In this study, we attempted to realize a transparent moisture-absorbing film with LLDPE as the resin material and 50% nano-sized zeolite addition. However, the higher the zeolite content, the more difficult kneading and film-forming processes become. In fact, by using the blown film extrusion and cast film extrusion processes, it was impossible to form a film by tearing after extrusion when film processing was attempted by adding nano-sized zeolite with a surface modification treatment that produces high transparency. The results of our attempts to improve the problems from these results, it was found that a combination of a surface modifier that is highly effective in increasing the refractive index of the particles to increase their transparency and a modifier with excellent processability can be useful to facilitate kneading and molding. As a result, it was confirmed that resins containing 50 wt% surface-modified zeolite with such two surface modifiers could form 30 micrometer-thick films without dilution.