Composite of tricalcium phosphate (TCP) and poly(lactic acid) (PLA) was attracted attention as a material of bone fixation device which was used fracture treatment, because of bioabsorbable and osteoconductivity. However, the mechanical properties of this TCP/PLA composite are degraded due to stress concentration at the interface between TCP and PLA. In this study, hybrid reinforcement combining the interfacial treatment on TCP surfaces with stearic acid and tensile drawing of TCP/PLA composites was proposed. TCP/PLA composite without internal treatment was drawn and tensile tested. This result showed that molecular chains were oriented with extrusion ratio (ER), and tensile strength and elastic modulus increased. On the other hand, the tensile strength of TCP/PLA treated with at the interface with static acid increased without drawing. This may be due to improve of interfacial adhesion by the interfacial treatment. And, the tensile strength and elastic modulus of drawn TCP/PLA increased with interfacial treatment with stearic acid. The orientation function of the interfacial treated TCP/PLA was higher than that of the untreated one, although both ER were same. This might be that due to stearic acid acting as a plasticizer and improving the mobility of PLA molecular chains.

A database was created to centrally manage a total of 8,600 files of documents, photos, videos, and web information related to molding of CFRP/CFRTP. Since then, the rate of automation has increased. Forged carbon and automated tape using robots have become the mainstays, and hot press molding of CFRTP plates is rare. Robotization, IoT, and AI are important.

In this study, the bonding strength of epoxy adhesives was evaluated using small columnar specimens to improve the reliability of epoxy adhesive joint. The effects of adherend and anodic oxidation of A5052 adherent on the bonding strength were investigated. The experimental results showed that the bonding strength and fracture morphologies of the epoxy adhesive depended on the adherend. The anodic oxidation of A5052 improved the bonding strength. However, due to the high temperature and humidity environmental loading, the bonding strength of the anodized A5052 adherend decreased nevertheless the bonding strength of the non-anodized A5052 adherend increased. The bonding strength of the grass epoxy adherend increased by the high humidity environmental loading.

Thermal barrier coatings (TBCs) are used in hot sections of aero-engines and land-based gas turbines for increased efficiency and extended life of superalloy components. Recently, the suspension plasma spray (SPS) technique has attracted attention as a new method of using submicron spray powder as the suspension. Because of using submicron fine powders, the SPS technique can fabricate coatings with unique microstructures, such as columnar and cauliflower-like structures. In this study, the double-layered TBCs consisting of YSZ and YbTa3O9 were prepared using the SPS technique. Based on the thermal cycle fatigue test results, the effect of microstructure on the thermal fatigue property of the SPS-TBCs was discussed.

To clarify the effect of alloying elements (Si, Cu, Cr, Ni) on fatigue properties, fatigue tests of low-carbon steels were carried out with smooth plate specimens. The test results revealed that addition of Si and Cu was effective for enhance fatigue limit ratio. New fatigue-resistant steel has been developed by means of optimization of these alloying elements for commercial applications. Results of fatigue test using the full-thickness specimens indicated that the developed steel had excellent fatigue properties compared to conventional 490 MPa class steel. The fatigue strength at 107 cycles was improved by 36% compared to conventional steel. The observation of fatigue cracking showed that the crack initiation was delayed in the developed steel, thereby resulting in remarkable improvement of the fatigue life.

The electrode materials for lithium-ion batteries are microscopically connected by a polymeric binder that does not affect the electrolytic reaction of the active material in powder form. In this study, tensile fatigue test and plane bending fatigue test were conducted on electrode materials fabricated with various binder concentrations to investigate the mechanical fatigue properties of the binders that support the structure of the electrode materials. A mechanical model approximating the microscopic structure of the electrode material proposed in this study was used to estimate the fatigue properties of the binder. From the results of the tensile fatigue test, it was found that the binder causes energy dissipation and superposition, which leads to macroscopic fracture of the electrode material. The S–N curves of the specimens with low binder concentration predicted based on the results of the tensile fatigue test were safe evaluation against the results of the plane bending fatigue test.

Plastic materials have some environmental problems such as marine pollution caused by microplastics. Therefore, composites of poly(lactic acid) (PLA) and cellulose nanofiber (CNF) have been attracted attention because the CNF/PLA composite has degradability in the natural environment. However, the mechanical properties of the CNF/PLA composites are low. This is due to the low compatibility between CNF and PLA, and to obtain interfacial delamination. In this study, shrinkage of matrix due to crystallization in CNF/PLA composite was focused on as a method of physical interface treatment. The CNF/PLA composite was annealed, and the mechanical properties of this annealed CNF/PLA composites were investigated by tensile test and Vickers hardness test. Tensile test results showed that the elastic modulus of the annealed CNF/PLA composite increased slightly due to crystallization, but the strength decreased significantly. This decrease in strength may be due to crystal coarsening, interface delamination, and residual stress. On the other hands, Vickers hardness of CNF/PLA composite increased with annealing. And, matrix crystallinity of CNF/PLA composite also increased. However, this increase of hardness was small considering the shrinkage of the matrix due to crystallization. This might be due to the relaxation of residual stress during annealing.

This paper reports on the process of manufacturing thin A6061 sheets by vertical twin roll casting. Currently, aluminum sheet is generally manufactured through processes such as face milling, cold rolling, hot rolling, and annealing after steelmaking. This leads to multiple processes and high manufacturing costs. The twin-roll casting method can solve the above problems because it can produce thin sheets close to the product thickness directly from molten metal. In addition, thin sheets produced by the twin-roll casting method solidify rapidly in the gap between the two rolls, resulting in finer grains and improved mechanical properties. The equipment used in this study is a vertical twin-roll casting machine of the twin-roll method, in which the rolls are arranged horizontally and molten metal is fed from the top of the equipment. In this study, experiments were conducted to improve the productivity of thin aluminum sheets. Thin sheets of aluminum alloy A6061 were produced by vertical twin roll casting, and the conditions under which they could be produced were investigated. The effects of roll speed on surface properties and rolling load were also investigated. Furthermore, the characteristics of twin-roll casting were evaluated by observing the microstructure of the produced thin sheets.

This paper reports on the vertical twin roll casting of aluminum alloy A7075. Aluminum alloy A7075 belongs to the highest strength alloys and its sheets are produced by rolling and extrusion. It is used in the aerospace industry and for special applications, but it has a high susceptibility to solidification cracking and is difficult to obtain sheets easily. Twin-roll casting can produce thin sheets directly from molten metal, making it possible to produce plates from alloys other than conventional sheet alloys. In this study, a new apparatus was designed and fabricated to conduct research under low speed and high pressure, which is more suitable for continuous casting of A7075 sheets than previous studies. The new apparatus is compact and has narrower roll widths, so that the load per unit width can be increased. The effects of roll speed on sheet continuity, surface properties, thickness, and microstructure were investigated.

Semi-solid forging is a forging method in which slurry in a semi-solid state is forged using a die to obtain a near-net-shape that is close to the finished product. Compared to casting and cold forging, semi-solid forging has the advantages of better dimensional accuracy and lower forming load. The objective of this study was to increase the strength of magnesium alloys, which are lightweight among practical metals and have excellent mechanical properties such as high specific strength and electromagnetic shielding properties. The molten metal was stirred during slow cooling to refine and spheronize the crystals, followed by semi-solid forging using a servo press. This resulted in an evaluation by a compression test in addition to verification of formability. The load-stroke diagram indicated that semi-solid forging was feasible for four materials under the experimental conditions. However, cracking and burring occurred under some conditions. Stress-strain diagrams from the compression tests showed that the ductility of AZX912 was improved by the semi-solid forging, while no difference was observed in AZX1312, AZX1712, and AZX2112 depending on the solid phase ratio．

We report on the fabrication of high-performance components of aluminum alloy A7075 by the semi-solid forging method. Semi-solid forging has the advantages of better dimensional accuracy and lower forming load compared to casting and cold forging, and semi-solid materials are expected to have improved mechanical properties compared to normal materials. Products with complex shapes are manufactured by die casting. However, there are few reports on die casting of A7075, which has high tensile strength, because it has high deformation resistance and is prone to solidification cracking and hot cracking. In this study, two differently shaped parts fabricated by an optical 3D printer were embedded in a semi-solid slurry during semi-solid forging of aluminum alloy A7075 to fabricate a test piece with an internal cavity. The feasibility of forming the specimens was investigated by measuring the die cushion load during forming, measuring the extent of the internal cavity, and observing the surface properties of the specimens.

VaRTM (Vacuum Assisted Resin Transfer Molding) is one of FRP molding methods, in which resin is impregnated into dry fiber preform by making the resin flow in a vacuum bag using a pressure differential. The authors have previously shown that in RTM molding using a molding die, the impregnation and curing of resin into fiber bundles can be monitored by ultrasonic measurement from outside the mold. In this study, the applicability of this method to VaRTM molding is investigated. It was found that both the resin impregnation and curing processes can be monitored by ultrasonic waves, although it is necessary to pay attention to changes in plate thickness.

In the 3D printing with FDM printer, thermoplastic resin filaments are heated and melted by the printer head and then laminated layer by layer, so the specific gravity of the printed products is almost the same as that of the material. Therefore, a reduction in the filling density is necessary to reduce the weight of the printed products. However, printed products with low filling density have weaker mechanical strength due to the mesh structure. In this study, original filaments were prepared by mixing inorganic hollow particles during filament regeneration, and 3D printing of lightweight composites without reduction of the stiffness is attempted. The effects of the base resin on 3D printing with original filaments was also investigated. It was found that both the stiffness improvement and weight reduction of the filament is possible by including hollow particles. However, due to molding defects during specimen fabrication, the stiffness of the printed specimen could not be improved. It is expected that further improvement in stiffness is possible if the molding accuracy is improved.

Honeycomb panels are widely used in industry because of their light weight and high rigidity. Generally, straight cells are arranged perpendicular to the panel surface, but we have reported that helical twisting of the cells can improve the bending stiffness without increasing the weight. In this study, compression properties of helical honeycomb panels were investigated by FEM analysis. Since it is expected to occur large deformation in helical honeycomb panels, large deformation analysis was conducted in addition to linear analysis. Moreover, compression test of 3D printed honeycomb panels were also carried out. It was found that the difference of compression stiffness between the large deformation analysis and the linear analysis becomes larger for panels consisting of helical cells. Experimental results indicates that both the compressive strength and compressive stiffness decrease as the helical diameter increases, while the load drop after yielding becomes smaller in the honeycomb panel with large helical diameter.

For a carbon neutral society, lightweight and high-strength CFRP hydrogen storage tanks have been developed. In order to operate CFRP hydrogen tanks, it is necessary to establish their maintenance method. Conventional inspection method such as visual inspection and thickness inspection are not sufficient for the degradation of CFRP layers due to matrix cracks and fiber fractures. Therefore, it is desirable to establish a non-destructive testing method suitable for CFRP hydrogen tanks. In this study, the ultrasonic propagation characteristics of CFRP/aluminum laminate was evaluated for ultrasonic inspection of a TYPE 3 hydrogen tank, in which carbon fiber wrapped around the entire circumference of an aluminum liner. Multipoint measurements were performed using a laser Doppler vibrometer, and wavefront images were constructed from waveform amplitudes at each time. Especially, the effect of CFRP laminate configuration on ultrasonic propagation characteristics was investigated. The results showed that ultrasonic wavefront of the CFRP layer is affected by the underlying aluminum plate, and the effect is more pronounced when the difference in propagation velocity between the CFRP layer and the aluminum plate is large.