Ceramic is an important material in industry, but it is said that the firing process accounts for about 60% of the energy consumption in the entire manufacturing process. For this reason, exhaust gas during firing has become an environmental problem, and non-firing ceramics that are solidified by a chemical reaction without firing are attracting attention. In this study, we analyse the reaction process of non-firing ceramic using the molecular dynamics method, which is a simulation method. In the activation calculation using the indenter, an original model with one indenter and an increase model using indenters with multiple diameters changed were used. As a result, it was confirmed that the internal structure of the ceramic material particles was activated in the increase model using multiple indenters. In addition, in the calculation of arranging water molecules on the activated surface, new bonds via water molecules were found. However, there was no difference in intensity between the two models.
In this study, distribution of impulse load caused by shockwave associated with lightning strike was analytically estimated to clarify the effects of mechanical load on lightning strike damage of CFRP laminates. Finite element analyses (FEA) were conducted to simulate displacement response on rear surface of specimen Pressure distribution was parametrically examined to simulate the dynamic load distribution caused by lightning strike by compared with the experimentally measured specimen deflection which was obtained by simulated lightning current test. As results, by applying estimated impulse load distribution, maximum displacement response obtained by FEA at the center of specimen roughly agreed with the experimental result. However, displacement history at center of specimen and deformation shape showed significant difference between experimental and numerical analysis result. For a precise estimation of pressure distribution caused by lightning strike, more detailed parameter fitting is required
A method of performing ultrasonic fatigue tests on L-shaped carbon fiber reinforced plastic (CFRP) laminates was suggested in this study. Ultrasonic fatigue tests are generally conducted by resonating a specimen. In order to perform the ultrasonic fatigue tests, the specimens need to be resonant at a frequency of 20 kHz. The specimen geometry was determined based on the results of finite element analysis (FEA). The specimens were evaluated in terms of displacement and temperature experimentally whether the ultrasonic fatigue tests could be performed. It was confirmed that the specimens resonated and the curved section of CFRP laminates were subjected to higher stress. In the ultrasonic fatigue tests, delamination was observed in the curved section of CFRP laminates. Considering these results, the ultrasonic fatigue tests could be performed on L-shaped CFRP laminates. Although the bending and torsional deformation occurred analytically in the specimens, it was concerned that the influence of torsional deformation was small in terms of measuring displacement amplitude of the specimen end.
To evaluate the fatigue damage behavior of a unidirectional carbon fiber reinforced plastic (CFRP) laminates, interim stopping tensile fatigue tests with acoustic emission (AE) measurements were performed on specimen with a notch. The relationships between damage behavior and AE behavior were characterized. From the results, splitting occurred from a notch and rapidly progressed for all specimens. Also, the relationship between the obtained damage behavior and AE behavior suggests that damage can be identified by comprehensively evaluating the frequency band of the AE wave and each AE parameter. We also compared the results of each CFRP laminate and investigated the effects of carbon fiber types on splitting growth behavior and AE behavior. The length of splitting at the cycle limit value and the splitting growth rate tended to be different for each CFRP laminates. We considered that splitting growth behavior was affected by the stiffness of CFRP laminates, stress condition and interfacial strength between fiber and matrix.
In order to investigate the effect of ply thickness and stacking order on the mechanical properties of CFRP laminates, five different laminates were prepared using two different types of prepregs with different layer thicknesses. All the laminates were cross-ply and only the stacking order was changed. Static tensile tests, tensile fatigue tests, and DMA tests were conducted for evaluation of their mechanical properties. In the tensile tests, it was found that the tensile strength was higher for the thin-ply laminates than that of conventional laminates. There was no difference in tensile strength due to the stacking configuration. Fatigue tests also showed that the thin-ply laminates had low fatigue strength at high cycle fatigue. In particular, the thinnest configuration laminate showed a significant reduction in fatigue strength, and the fracture morphology of the thinnest configuration laminate was different from that of the other laminate as observed by the microscope. In the DMA test, no difference due to ply thickness or stacking order was observed.
The aim of the present study is to elucidate the possibility of improvement of filler dispersibility of polymer composite by using hybridized hydrophilic silica nanofillers with carbon black (CB) particles. The experimental techniques of the fabrication method of polypropylene (PP) composites were investigated on the basis of the strategy for the preparation of hybridized fillers of silica and CB, silica@CB fillers, having packing structure controlled as loosely as possible to enable easy peeling silica primary particle from CB to an isolated dispersed state at a blending stage with the polymer matrix, PP, melt. In addition to these PP composites fabricated by adding 2.5 vol% of the prepared silica@CB fillers directly, the tensile tests of the PP composites co-added with individual hydrophilic silica nanofillers and CB particles at the same volume fraction were also performed in this study. It was found that the hybridization of the nano-silica and CB particles used as fillers might improve the filler dispersibility and the tensile properties such as the stiffness, strength, and toughness of the PP composite system with these nano-silica and CB fillers.
In recent years, Vacuum assisted Resin Transfer Molding (VaRTM) process is attracting attention so that FRP products can be obtained at low cost than the autoclave. VaRTM process is a method which thermosetting resin is impregnated to fiber base material by vacuum pressure. Many types of equipment have been used for VaRTM process. It has been reported that arrangement of subsidiary material affects the impregnation rate. Therefore, permeability which indicated to resin impregnation properties is the key parameter in VaRTM process. In this study, effect of measurement conditions on permeability of Non crimp fabric (NCF) was investigated. Permeability was calculated by measuring the impregnation behavior of epoxy resin into NCF and using Darcy's law. This study suggested that the resin supply position and the inner diameter of the hose are influential factors of permeability.
In this paper, to investigate the mechanical properties of V-shaped carbon fiber reinforced thermoplastics (CFRTP), four-point bending tests and step-by-step interrupted four-point bending tests were conducted. The test was carried out using similar testing tool to ASTM D 6415. Also, in order to evaluate the validity of CFRTP, it was compared with V-shaped carbon fiber reinforced thermosetting plastics (CFRTS) molded vacuum-assisted resin transferred molding (VaRTM).V-shaped CFRTP were molded with a bending-type V-shaped mold which has an angle of 90°. CFRTP studied was plain woven carbon fabric reinforced polyamide 6 (PA6). Pre-consolidated laminates were preheated above the melting temperature of PA6 and then pressed after transferred to the V-shaped mold. CFRTS studied was compounded of plain woven carbon fabric as the same used CFRTP and epoxy polymer. As a result, in the case of CFRTP, it was suggested that the difference in the damage process occur with changes in molding temperature. Also, the difference of interlaminar tensile strength and the damage modes between CFRTP and CFRTS was observed.
A carbon fiber reinforced thermoplastic (CFRTP) sheet was made by a plain-woven carbon fiber fabric and thermoplastic polyimide. Two types of the L-shaped CFRTP specimen were fabricated by hot-pressing of laminated sheet or hot-pressing of pre-consolidated laminated sheet. Wrinkle of fiber was not observed in the L-shaped CFRTP specimen by laminated sheet but observed in the specimen by pre-consolidated laminated sheet. Four-point bending tests on the L-shaped CFRTP specimens were performed and the interlaminar tensile strengths were calculated. The L-shaped CFRTP specimen by laminated sheet showed higher interlaminar tensile strength than the specimen by pre-consolidated laminated sheet. Small delamination parallel to the wrinkle was developed at the relatively low stress condition for the L-shaped CFRTP by pre-consolidated laminated sheet which degraded the interlaminar tensile strength.
The internal strains of the carbon fiber-reinforced plastic (CFRP) laminates were monitored in real time during machining (drilling), and the relationship between the monitored strain and the machining damages was investigated. The internal strain and temperature around a drilled hole with a nominal diameter dnom were respectively measured using a fiber Bragg grating (FBG) sensor and a thermocouple. Machining damage (delamination) with various sizes was introduced using drill bits for steels and CFRPs. The maximum delamination size dmax and the distance of the FBG sensor from the delamination edge were measured using soft X-ray radiography. The absolute strain, consisting of the process-induced internal strain and the machining-induced internal strain, was then plotted against the delamination factor dmax/dnom. It was revealed that the absolute strain was correlated with the delamination factor and the relative distance of the FBG sensor, and that the absolute strain with the true value and sign (tensile or compressive) is more helpful than the strain change before and after the drilling.
This study creates a blood vessel model for a catheter surgery simulator. In previous study was succeeded in producing a blood vessel model applicable to a surgical simulator using PVA hydrogel. On the other hand, the problem with the blood vessel model is that the reproducibility of the mechanical properties of blood vessels, which is important for the actual catheter operation sensation, is low. Therefore, in this study, creates a blood vessel model with a two-layer structure that reproduces the mechanical properties of the blood vessel wall and adipose tissue. In the proposed blood vessel model, it is shown that the mechanical properties can be reproduced by changing the compounding ratio of powdered PVA and the mass ratio of water and DMSO as a solvent. Furthermore, this study proposes a method for producing a two-layer structure and show that it is possible to produce a blood vessel model with a two-layer structure.
In internal combustion engines, the number of repetitions of start and stop is increasing due to the introduction of idling stop system, and reduction of the friction and improvement of seizure resistance are strongly demanded. Overlay technology is one of the effective means for these problems in journal bearings. This study describes tribological properties of curved plain bearings with polymer overlay containing solid lubricant, such as molybdenum disulfide powder and graphite powder. Polymer overlays were coated on bearing metals by roll coating method. Interval friction tests were carried out by repeating start and stop, and the friction characteristics were evaluated by the maximum value of the friction coefficient at the start of each cycle. As a result, in the case of the overlays containing 40 vol% of graphite, friction coefficient at the start of each cycle showed low from the beginning and gradually decreased.
The purpose of this study is to clarify the effect of additional elements on the superplasticity in the Sn-Bi alloys. Tensile tests of Sn-Bi-X alloys were performed at various temperature (298, 313, 333, and 353 K) and strain rates (from 5.25×10-5 to 5.25×10-2 s-1). It was found the superplastic behavior at high temperature (more than 333 K) and low strain rates (under 5.25×10-4 s-1). Strain rate sensitivity “m” for Sn-Bi-X alloys were less than 0.3. From the results of the microstructure observation after superplasticity, it was found that the additional elements act as the formation of intermetallic compounds or dissolves in the primary crystal Sn grains had an effect on the superplastic deformation of Sn-Bi-X alloy.
It is important to improve fatigue characteristic of metallic materials to prolongate fatigue life. In this study, high current density electropulsing was applied to polycrystalline copper, and its effect on the formation and growth of Persistent Slip Band (PSB) was evaluated. Specimen was subjected fatigue loading conducted by displacement control. Using replica method, extrusion formed on specimen surface was observed. High current density electropulsing was conducted when arbitrary fatigue test had accomplished. After each cycle, the differences in growth of extrusion with and without the application of electropulsing were observed using Atomic Force Microscopy (AFM). As a result, it was turned out to be that electropulsing has following effect; (1) extrusion growth delays (2) extrusion height decreases. Polák’s vacancy model was applied to these experimental results. Electropulsing causes acceleration of vacancy diffusion existing channel of PSB towards PSB wall or matrix vein. Reduction of vacancy concentration induces suppression of atomic flux from PSB channel to matrix vein until vacancy concentration leads to its saturation again. It is thought that in this duration, extrusion growth keeps suppressing.
A6061 and SPC270 plates with a thickness of 1mm were successfully welded by lap friction stir welding at tool probe. The effect of the tool probe plunge depth on the mechanical strength and the microstructure of the weld was investigated by tensile shear strength test and microstructure observation. The maximum tensile shear strength of 1749 N was obtained at tool probe plunge depth of 0.05 mm. The cross-section microstructure of the weld showed smooth weld interface without hook structure at outer periphery of the probe trace and intermetallic compound layer at the retreating side of the weld.
Film boiling is a heat transfer phenomenon at a solid/liquid interface in which the liquid phase is boiled to cover the solid with generated vapor and maintain steady heat transfer when the heat flux from the solid surface to the liquid phase is large enough. Using a carbon fiber preform as a solid phase and an appropriate organic solvent as a liquid phase, when the solid/liquid interface is heated to a high enough temperature by induction heating, a vapor film of organic solvent vapor is formed on the carbon fiber surface, and the pyrolytic carbon generated from the vapor can be rapidly deposited on the carbon fiber. This phenomenon has been investigated as a way to form matrix carbon in C/C composites by a film boiling method. Characteristics of the film boiling method have been found that C/C composites formed have high density of the matrix carbon, a significant degree of graphitization by post-heat treatment, and a substantial reduction in the process time required for densification. In this study, an application for the bonding of graphite rods was investigated by using carbon deposition reaction with the film boiling phenomenon.
An open-cell nickel foam was joined with a polymethyl methacrylate (PMMA) sheet with a thickness of 1.0 mm by friction stir incremental forming (FSIF) process under rotation rate of the tool faster than 2000 rpm and feed rate of the tool slower than 60 mm/min. The joining strength between the foam and the sheet was obtained over the fracture strength of the foam in uniaxial tensile test. On the other hand, the compressive specific strength of the foam–sheet composite was obtained approximately 33 times higher than that of the foam in uniaxial compression test. This was due to not only high specific strength of the sheet but also sandwich structure of the foam–sheet composite.
For evaluation of stress at the interface of the bonded part in previous studies, the singular stress field has been evaluated by the stress intensity factor and the singular stress index by finite element analysis. However the evaluation method of the actual stress distribution has not been established. It is necessary to estimate the stress generated in the bonded part without invasiveness. In this study, we propose a method to estimate the actual stress distribution generated at the interface of the bonded part by using the deformed shape data of the structure by finite element analysis based on the strain increment theory for the bonded body. A peeling test was conducted on a test piece in which a 0.3 mm thick aluminum plate (A1050) and a 5 mm thick aluminum plate (A2017), was adhesively bonded using a thermosetting epoxy adhesive sheet. The effectiveness of the proposed method was investigated.