Superplasticity of polycrystalline metallic materials is the phenomenon that shows hundreds to thousands of percents of large plastic deformation without necking in a steady state of low stress, under some specific thermo-mechanical conditions (some limited ranges of high temperature and low strain rate). In this research, the superplastic deformation of the magnesium alloy (AZ31Mg alloy) which is super lightweight but hard to process was investigated by the microscopic observation of microstructure after several kinds of loading. In this paper, the obtained results are shown and discussed.

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The ductile fracture of materials is caused by the void growth and linking. So, it is important to evaluate the damaged condition of ductile materials which contain many voids. In this study, the new way to evaluate the damaged condition of porous material with elliptic holes, using equivalent net stress is proposed. The validity of equivalent net stress in biaxial deformation was examined experimentally. As a result, correlations between equivalent net stress and experimental results were varified only when volume fraction of holes are approximately 1.7%, and to improve the validity of evaluation of damaged condition on the other volume fraction, it is needed to adopt new facters affecting to the ductile deformation of materials.

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The point defect dependence of the longitudinal wave velocity indicates the elastic stiffness degradation due to plastic deformation damage which is closely related to the deformation instability mechanism. Therefore, in this paper FEM numerical simulations regarding to the contour line of amount of point defects estimated by the calculation of the intersected cross slip among dislocations under several proportional loading paths are performed and compared with the experimental results of necking onset strains in aluminum specimens measured by laser speckle method. The good agreement between the simulated and experimental results regarding the onset of the deformation instability suggests that the proposed algorithm to calculate the amount of point defects caused by intersected cross slip among dislocations has ability to be unified criterion for both localized and diffused neckings.

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This study investigates the effects of prediction method of Stress Redistribution Locus (SRL) method in creep relaxation process by comparing to the previous method using elastic follow up approach. The SRL method can predict the experimental results better than the previous method for the perforated platemodel.

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The evolution equation of self-repairing is proposed based on the constrained growth model of the cavity by Dyson and continuum damage mechanics. The constitutive equation of creep by Suzuki and Hamanaka based on kinematic/isotropic hardening theory is extended to take into account the effect of damage. The constitutive modeling is identified, based on tensile creep test and sintering test by compressive loading after tensile creep for two steels, SBV2 and SUS316HTB. Consequently, the validity of the proposed modeling is illustrated through the simulations for the self-repair process of two kinds of steels damaged by creep.

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In this study, the inelastic analysis of an ultra fine plate-fin is performed based on a homogenization theory. To this end, the homogenization theory of non-linear time-dependent materials, which was developed by the present authors, is applied to the analysis. Moreover, utilizing the point-symmetric structure of plate-fin, the domain of analysis is reduced by half. Then, the elastic-creep deformation of ultra fine plate-fin made of Hastelloy X under uniaxial tension or simple shear at 950℃ is analyzed by using the homogenization theory. It is thus shown that the macroscopic elastic-creep behavior of plate-fin exhibits significant anisotropy. It is also shown that the marked variation of macroscopic bulk strain of plate-fin is caused by the loading in the staking direction.

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Now, almost of screws are produced by the Thread-Rolling technique. But, its accuracy of forming is bad, compared with cutting because the thread-rolling gives priority to high productivity. In recent years, CNC rolling machine was developed which is high accuracy in screw forming. So, use of the thread-rolling is increasing. Consequently, the simulation of the thread-roling is required in order to predict transformation locus and processing conditions. In this reserch, it is the object to recreate and analysis transformation locus in the threadrolling and to predicte processing conditions by Three-Dimensional Rigid-Plastic FEM.

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Railway vehicle has required the safety of passengers and crews in collision. The development and study of crushworthy structures which are able to absorb the energy of collision are widely carried out in Europe and the United States. This paper deals with the FEA and experimental study on the mechanism of progressive buckling about Aluminum Hollow Extrusions, using moire topography and cutting-method of the test piece as well as explicit FEA.

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In this paper a research problem for investigating the elasto-plastic behavior when a laser beam was irradiated to the surface of a thin metal plate with cooling its backside is described. When the plate is cooled down until the room temperature after the first irradiation, the plastic deformation spreads at the neighborhood of the first irradiated position and the residual stress distributes over the plate. Hence, the distributions of internal forces at the second irradiation become very complicated, and the conditions for re-yielding will closely depend on the position of re-irradiation. In this study, we investigate the relation between the generalized internal force arriving at re-yielding and the position of the second irradiation. Especially, we reveal the feature of the inside area and the outside area of the plastic region which occurred at the first irradiation.

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In the automobile body structure, thin walled box section beam performed in irregular pitch spot welding is used. Shearing force is transmitted through the spot welding, when the body structure is distorted, and torsion and bending affect the member. In case of the spot-welded beam in irregular pitch, the shearing force at each spot welding is different, and it is a statically indeterminate problem to solve the shearing force. In this paper, the theory, which analyzed stress distribution of spot-welded box section beam in irregular pitch under torsion, was proposed. By comparing the analytical result with finite element method result and experimental result, the effectiveness of this theory was shown.

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This paper describes a new foil welding technique and its experimental results. When an impulse current from a capacitor bank passes through a flat one-turn coil, a magnetic flux is suddenly generated in the coil. Eddy currents are induced in two insulated metal plates and overlapped vaious foils for example aluminum, copper, stainless steel, Fe-Ni alloy between the plates placed in the coil. The foils can be welded both by the magnetic pressure applied onto them and by Joule heat generated in them. The bank energy required for welding of 20mm in length is less than 2kJ.

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In this paper, steady-state Eulerian thermal analysis of welds using moving coordinates is shown. This analysis has been reported as much more computationally efficient method than conventional transient Lagrangian method in which moving heat source actually moves in a computational domain. To show convenience and availability of the Eulerian method, we adopt a computational fluid dynamics code, applied the double ellipsoidal power density distribution model proposed by Goldak et al.(1984), considered temperature dependency of thermal properties, and analyzed a groove weld of a core shroud in a boiling water reactor (BWR). Comparison of the analyzed temperature histories to the measured results shows that the numerical results reproduce the measured results well.

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The authors have been doing the research work of forming spur gears through cold extrusion method. Even for the carburized material, the complete spur gear (module m=1.25, number of tooth Z-=18) can be formed by this method. So the bending strength and hardness distribution of the cold extruded spur gear tooth formed from carburized workpiece were examined. It is found that the bending strength of this gear tooth after induction hardening heat treatment is greatly increased compared to that of cut gear tooth after the same induction hardening heat treatment.

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Performance tests of easy coating-type lubricants of cold forging were conducted under realistic tribological conditions of real forging using a localized rod drawing method. Effects of surface expansion and interface temperature on tribological characteristics were clarified. The surface expansions were varied using various wavy dies which can induce various arbitrary surface expansions. The interface temperatures were varied by temperature regulator. The test method presented here was demonstrated to be very effective for the evaluation of easy coating-type lubricants of cold forging.

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We studied the relation between flow instable phenomenon and molecular structure of polymer chain with some commercial HDPE (High Density Polyethylene) melts. In this study we analyzed molecular strucuture through using Gel Permeation Chromatography equipping with flow cell type FT-IR (GPC-FTIR). We showed that one of the origins of the flow instable phenomenon could be ploymer chains' structure. (Polymer Chain Branching)

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Effect of fiber fraction and water absorption on fracture toughness for glass reinforced polyethersulfone was studied. Fracture toughness of G20 specimen (W_f=20%) is higher than G30 specimen (W_f=30%). The relationship between fracture toughness and fiber weight fraction is not linear. By observing fracture surface and inquiring Acoustic Emission (AE) characteristics of micro-failure process, it is found that primary micro-failure is fiber pulling-out. And it is also found that pull-out of G20 specimen is larger scale than that of G30 specimen. Then, fracture energy of G20 specimen is higher than that of G30 specimen. And this means same tendency in fracture toughness. But fracture toughness is increases by water absorption. It is because of PES resin becoming more ductile by water absorption. Increasing ductility increases fracture energy and fracture toughness.

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Most of shape memory alloys (SMA) are functional intermetallics with the shape memory effect and superelasticity, and are expected to be the smart materials. In future, these materials will be applied to various fields, for example science and technology, energy and medical field. In the present paper, the microstructure and chemical composition in TiNi alloy was observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. Especially, precipitation phase occurred into TiNi alloy was discussed with the focus on the microscopic properties. As the results of EDX method, the nominal TiNi alloy was mainly composed of 49.56 at% Ti and the others. But the precipitate region was occupied by about 95.45 at% Ti, and approximately become single phase. The Ni-rich phase was not confirmed around of the precipitation of Ti. The precipitates crystallized, and the crystal structure was cubic. The lattice spaces were d_<121>=1.300 A and d_<200>=1.531 A, determined by the electron beam diffraction image. Then the lattice constant was α=3.062 A.

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The cavitation is foaming phenomenon by the phase change from the liquid to the gas. It is well known that the very high shock wave the cavitation foam collapses is generated, and the shock wave is intentionally generated, and it seems to obtain the high peening effect, if it is treated on the material surface. Then, considering the application to chemical plant, the cavitation was generated using representative austenite stainless steels SUS304 using the ultrasonic vibrator, and the peening processing was conducted to the sample surface, and the effect was examined.

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The ultrasonic welding technique can be carried out in many different ways, such as in direct welding metal/metals. This paper gives a description of an experimental study of the ultrasonic welding of aluminum and cupper at room temperature, both quickly and easily when compared to other welding methods. For example, the ultrasonic welding of Al/Cu can be accomplished when the conditions of amplitude:20μm, welding pressure: 30MPa, at a required duration of 0.5s under the water bath. Ultrasonic welding in water bath was required high welding energy compared with room temperature.

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This paper deals with the fabrication and the characteristic evaluation of "green" composites in which polyvinyl alcohol (PVA) was used as matrix resin. Bamboo fibers were used as reinforcement of these "green" composites. These composites were made by hot-pressing method. Firstly, it describes the comparison of water resistance of new water-soluble polymer and general PVA. The new water-soluble polymer has good water resistance. Next, the tensile properties of "green" composites molded at various temperature, pressure and fiber content. The molding temperature was changed every 10℃ from 140℃ to 170℃. The molding pressure was 30MPa and 60MPa. Fiber content was 25wt.%, 50wt.% and 75wt.%. The composites molded at 150℃, 30MPa showed the maximum tensile strength. Tensile strength and tensile modulus increased with increasing fiber content.

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In this paper, we tried to fabricate new "green" composites without using artificial polymers. Their fiber orientation is unidirectional. It was shown the composites can be made by hot-pressing over 60℃. The influence of molding conditions on their tensile behavior and flexural behavior was investigated by changing the molding temperature and pressure. The molding temperature was changed every 20℃ from room temperature to 180℃. The molding pressure used was 10MPa and 50MPa. Average tensile strength and Young's modulus of the composites molded at 120℃ and 50MPa were 322MPa and 37GPa, respectively. Their Young's modulus tends to increase with increasing molding temperature. Their fractured elongation tends to decrease with increasing molding temperature over 80℃. Average flexural strength and flexural modulus of the composites molded at 140℃ and 50MPa were 386MPa and 37GPa, respectively. The relationship between fractured elongation obtained by flexural tests and molding temperature is different from that obtained by tensile tests.

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The purpose of this study is to create an excellent toughness property, which cannot be exhibited by GFRP, for natural fiber green composites. By improving fracture strain of ramie fibers by means of mercerization, a unidirectional green composite reinforced by the fibers was dramatically improved in toughness. In tensile properties of the composite, additionally, deformation resistance increases with an increase in strain rate. This stress increase was quite useful for improvement of impact resistance. From the falling weight impact test, it was proved that the laminate composite (0°/90°/0°) using mercerized ramie pre-form sheets absorbed larger impact energy than the composite using untreated ramie pre-form sheets.

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To obtain composites with high strength in tension using bamboo microfibrillated cellulose (MFC) without any synthetic polymers as binder, the process to extract bamboo MFC and fabricating conditions were proposed. Bamboo MFC were extracted from the following five types of bamboo fiber bundles and monofilaments (pulps); (a) untreated fiber bundles (mechanically extracted from raw bamboo), (b) alkali-treated fiber bundles after mechanically extracted, (c) monofilaments obtained from steam exploded fiber bundles, (d) mono filaments from alkali-treated fiber bundles which were extracted by the steam explosion method, and (e) cellulose monofilaments chemically extracted from the monofilaments (d). These fiber bundles and monofilaments were ground at a high speed condition using stone disks to obtain the bamboo MFC. The composite was fabricated by hot pressing. The maximum bending strength of the composites was obtained at 160℃ under 120MPa when we used MFC obtained from (d) monofilaments. The maximum bending strength was 188MPa, which was about 2 times in bending strength of the composite with mono filaments (c).

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Lightweight composite made from kenaf and polypropylene fiber was fabricated with a press forming. The effects of number of layer, holding time and weight fraction on flexural modulus were investigated. The flexural modulus increased with increasing the number of layer and holding temperature. The increase of the number of layer contributed homogeneous PP dispersion because kenaf fibers were appressed each other and prevented PP from shrinking during heating. The increase of holding temperature contributed well wetting between kenaf and PP. These observations were revealed with SEM microphotographs. Moreover, the flexural modulus of composites showed at 43-50 percent kenaf weight fraction. This result indicated porous composites lower the optimized weight fraction than solid composites.

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Bagasse and polypropylene was mixed with a double arm kneading mixer, and palletized. The pellet was molded with an injection molding machine. The effects of weight fraction, injection temperature and pith on flexural modulus of composites and impact strength were investigated. The flexural modulus increased with increasing the bagasse fiber weight fraction under the rule of mixture, while the impact strength decreased. The flexural modulus and impact strength decreased with increasing injection temperature from 185℃ to 225℃. The optical photographs revealed that the fiber length of composites at 185℃ was obviously shorter than that at 225℃ despite the fiber length of pellets was equal. Furthermore, the flexural modulus and impact strength with pith 50% decreased by 7-10%. This seems due to the decrease of average fiber length.

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For the purpose of applying biomass sources to various industrial products, a bamboo powder composite was developed by injection molding. The matrices used for the composite were a cornstarch-based biodegradable resin (CP) and polypropylene (PP). To improve compatibility between the powder and matrices, alkali-treatment using NaOH solution was carried out for the powder. The results showed that tensile strength of the PP matrix composite increases largely if the alkali-treated powder is used as reinforcement, as compared to the composite reinforced by the untreated powder. The CP matrix composite was also improved in strength, though the degree of increase was not so effective. There may be an optimal NaOH concentration to increase mechanical properties.

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A poor bonding e resin and natural fiver is a problem in green composites. In order to make better composites, which have good bonding between resin and fiver, surface treatment methods by using such as NaOH solution have been proposed. In this study, unidirectional composite laminate which consists of PLA and kenaf string treated by NaOH solution was molded, and the effects of surface treatment on mechanical properties such as bending strength and transverse tensile strength were evaluated.

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In this study, the effects of two types of surface treatment for jute fiber reinforced polypropylene to the tensile properties are examined. One method is the treatment using Kakishibu juice, and the other one is heat treatment. Four kinds of persimmon density (25%, 50%, 75%, 100%) were used for Kakishibu treatment. The young's modulus of the composites increased by using treatment in the case of persimmon densities are (25%, 50%, 75%). When the density is 25% the young's modulus is highest. Four kinds of heating temperature (100℃, 110℃, 120℃, 130℃) were used. The young's modulus of the composites increased by treatment using heating temperature (110℃, 120℃).

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Biodegradable composites made from bagasse fibre before and after alkali treatments were prepared by a press forming, and the effects of alkali treatments on the fibres and composites were investigated. The composites reinforced with 1% alkali solution treated fibre showed maximum improvement in mechanical properties. After alkali treatment, the fibrillation occurred and the surface of the fibres got finer contribute to the improvement in fibre-matrix adhesion, and result in enhancing the mechanical properties of composites. Furthermore, the increase of strength and aspect ratio in the treated fibres also improve those properties. In comparison with the untreated composites, approximately 13% improvement in tensile strength, 14% in flexural strength and 30% in impact strength had been found, respectively. SEM observations on the fracture surface of composites showed that the fibre-matrix adhesion had been improved after alkali treatment.

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The strain rate sensitivity and gage length dependency of Bamboo fiber are investigated using Instron type tensile testing machine at room temperature. Ultimate tensile strength decreases with increasing gage length. In-situ observation of specimen surface during tensile test has been made to characterize the microscopic deformation and the fracture behavior of Bamboo fiber extracted using steam explosion method. Some kinds of such interfacial debonding are observed into fiber bundle. Simultaneous extension of delamination crackings and the fiber breakage, and subsequent incorporation of their microcracks into the main crack are observed.

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Fe_3Al was fabricated from Fe grinding swarf and aluminium can tip by powder metallurgical process. Mechanical alloying and pulsed electric current sintering were effective to form intermetallic compound. Fe grinding swarf and Al can tip were milling by mechanical alloying, and were subsequently sintered at 1073-1373K under 20-40MPa for 0-1200s by PECS. Relation between the microstructure and mechanical property was investigated.

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We have developed a fabrication method of a high aspect ratio nanoscale pit by a scanning tunneling microscope using a carbon nanotube (CNT) as the probe. The CNT probe used in this study is homebuilt CNT probe using CNT of 20-30nm in the diameter. The nanoscale pits were produced in Au thin film in an ambient pressure and room temperature. The results of our experiment show that the depth of the fabricated pit increased with the increase in the fabrication time, with little change in the diameter of the fabricated pit. We realized the fabricated pit of the diameter of 60nm with the aspect ratio of 4.5. Moreover, it was found that the fabrication method is applicable to not only Au thin film but also silicon single crystal. This demonstrates that CNT probes can be useful for fabricating nanoscale structures.

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We designed and fabricated a micro-inductor that may be used for hybrid electric circuits such as those in a mobile phone. The component was fabricated by superplastic die-forging of Pt-based metallic glass. This material exhibits Newtonian viscous flow in the supercooled liquid temperature range between the glass transition and the crystallization point. The working temperature was 543K, so a polyimide film was selected as a die material due to its good mechanical properties at elevated temperatures and its precision machinability. The die was fabricated with an excimer laser micro-machining system using the image-projection method. Laser ablation machining was carried out using a photomask in the shape of the micro-inductor. The photomask was fabricated using a lithography system. Superplastic die-forging of the metallic glass was carried out using this die, and micro-structures of the micro-inductor were easily fabricated. These fabrication processes demonstrate the advantages of metallic glasses and superplastic microforming techniques for mass producing micro/nano machine parts or devices.

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Superplastic forming of metallic glasses is useful for fabricating micro- and nano-devices. In the present paper, we studied glass transition and crystallization phenomena in Zr_<55>Al_<10>Cu_<30>Ni_5 metallic glass under rapid heating, at a rate of up to 10^6 K・s^<-1>. This material exhibits Newtonian viscous flow between the glass transition temperature T_g and the crystallization temperature T_x. During the heating, T_g and T_x increase and the normal viscosity λ decreases with increasing heating rate. As an application of this phenomenon, characteristic micro forming should be performed during rapid heating, at very high strain rates and under very low stresses, we developed a new micro forming system based on the characteristic behavior of Zr-based metallic glass under rapid heating. Using this apparatus, micro forging was carried out within a few seconds. Thus, the system would be most effective in the mass production of micro parts for MEMS.

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Metallic glasses are useful for fabricating nanodevices due to their low viscosity and homogeneity on nanometer scales. In this study, we developed optical components of metallic glass by superplastic nanoforming. Metallic glasses exhibit Newtonian viscous flow in a supercooled temperature range between the glass transition temperature and the crystallization temperature. This study used Pt-based metallic glass with a glass transition temperature of 502K. This material was applied to reflective interference optical components, and a diffraction grating (1μm interval) and a hologram were fabricated by superplastic nanoforming. Dies were made by Ni-electroforming, with master models fabricated by photolithography of the interference pattern. The working temperature of Pt-based metallic glass was 540K under a compressive stress of 10MPa. The results demonstrated the advantages of the superplastic nanoforming technique on metallic glass and for mass production of optical components.

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A fabrication method of patterns having different depths and an optional inclination of side-wall on a micro-flow device is developed using synchrotron radiation with the use of double masking process and the moving masks process. Preparing a micro-flow device with ribs along both sides of the micro-flow path was successfully done and this process is considered to be useful for the patterning technique when an adhesion step with a cover plate must be followed. Utilizing the device has made the adhesion process with a cover plate quite satisfactory, eliminating the need of surface-to-surface adhesion that often involves bubble inclusion between the plates. Also, it is a feature that the height of channel can be controlled within the limit of the ribs in the case of this process.

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In this study we developed a new molding process called "Melt Replication Process" to fabricate thermoplastic products with 3-dimensional geometry, thin wall, large area, precise microstructures, high optical-transparency, low residual stress and low birefringence under very low pressure less than 10MPa. Furthermore, we demonstrated its applicability to display parts and μ-TAS (Micro-Total Analysis Systems) chips. From our experiments using COP (Cyclo-Olefin Polymer), the products with microstructures ranging from tens of nm to hundreds of μm could be fabricated with transcript ratio over 95% and with very low pressure within short cycle time. Particularly, in the case of μ-TAS chip which has pillars with 20μm in diameter and 50μm in height, high replication ratios larger than 95% could be attained. Furthermore, the homogeneous transcription of microstructures over the large surface area of the molded product was confirmed.

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Diamond has become very important material for industry because the mechanical, thermal, optical and electrical characteristics. However, the machining of diamond is difficult for its high hardness. By the way, when cutting process is performed to ferrous material by a diamond tool, it is well known that the diamond tool will be worn severely. By utilizing of the tool wear, authors machined a diamond during cutting process of carbon steel. The purpose of this paper is to investigate micro machining of a diamond by this method.

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A conical punch with proper tip angle is used in the conventional forming of flaring or nosing on a tube end. The incremental forming is more effective for such a production, because the forming can be applied to various shapes with only one tool. In this research, miniature stainless-steel tubes ware deformed to flare and nose shape with bar tool, and characteristics of flaring and nosing were examined. The deformation behaviors in circumferential direction of two forming process were contrary to each other by direction of deformation and relative velocity of the bar tool transfer to the circumferential rotation at the outside of the tube. When the geometric ratio of diameter to thickness of tube was equated, the tendency of forming limit became almost the same. In case of large tool angle, the angle affected compressive force toward axial direction of the tube, and the forming limit declined.

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Flaring process is studied as one of thermoforming techniques for FRTP braided composite tubes in this study. The composite tubes are fabricated from cowoven braid by internal pressure bonding method, which consists of carbon braid and polyamide resin. The experimental results show that the flaring process is available as one of the thermoforming for braided composite tubes.

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[in Japanese]

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Effects of stress ratio on the fatigue behavior of CFRP laminates at room temperature have been studied. First, constant-amplitude fatigue tests are performed on quasi-isotropic and cross-ply CFRP laminate for six kinds of stress ratios. The experimental results demonstrate a marked stress-ratio dependence of fatigue behavior. The constant fatigue life diagram is linear in the range of a short life and it turns quadratic in the range of a longer life. To construct such a non-similar constant fatigue life diagram, a phenomenological procedure is developed on the basis of the static strengths in tension and compression and the reference fatigue strengths at the compression-tension strength ratio. The fatigue lives predicted using the proposed method agree well with the experimental results over the range of fatigue life up to 10^6 cycles for all the stress ratios tested. It is also demonstrated that the proposed fatigue life prediction method promisingly works for the off-axis fatigue behavior of cross-ply CFRP laminates.

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This study investigates an effect of time-dependent debonding propagation of fiber/matrix interface and that of stress concentrations to adjacent fibers from broken fibers on creep rupture lifetime in unidirectional composites. Above two phenomena are concerned to reduce materials strength and effect on creep rupture lifetime in unidirectional composites. A creep rupture model that takes into account the decrease of rupture strain due to time-dependent inter facial debonding propagation, based on the GLS rule is proposed and the rupture lifetime is predicted. It was found that the rupture lifetime is strongly dominated by the interfacial debonding propagation rate, and rupture lifetime is shortened considerably in case that time-dependent debonding propagation is remarkable. Subsequently, the change in the rupture strain due to the stress concentration without interfacial debonding propagation is estimated using a 3D shear-lag model and the rupture lifetime taking into account stress concentration is predicted using the McLean's creep model. Prediction result is compared with the result of Curtin-McLean model in which the stress concentration is not taken into account and the effect of stress concentration is investigated.

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Off-axis creep rupture behavior of unidirectional fiber-reinforced composites (T800H/Epoxy) under constant stress conditions at different temperatures (60 and 100℃) is examined. Tensile creep tests are performed at three different stress levels on plain coupon specimens with various fiber orientations θ=0, 10, 30, 45 and 90°. The transient creep behavior is dominant regardless of the fiber orientations. The ultimate creep rupture takes place along reinforcing fibers. Similar creep rupture behaviors are observed at 60 and 100℃. A damage mechanics model is then developed to describe the anisotropic creep rupture behavior observed. The proposed model can adequately describe the off-axis creep rupture behavior of the unidirectional CFRP. It is also demonstrated that the Larson-Miller parameter can be successfully applied to the creep rupture behaviors at 60 and 100℃.

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In this study, the purposes were to discuss about bending creep behavior on polyamide resin and glass fiber reinforced polyamide. First, to search the thermal characteristic, DSC test was performed. Next, to control GFRPA's crystallinity, it proposed a new heat-treatment method. Adjusting the crystallinity by the heat-treatment at 250℃ and different time became possible. Third, to search the effect of their crystallinity on bending creep behavior by 3 point bending creep test. As a result, the longer heating treatment time was, the more crystallinity was increased. Increasing crystallinity, creep deformation of these materials was reduced. Last, the effect of their fiber reinforcement on bending creep behavior was examined. As a result, the creep deformation and the progress of the transformation were controlled by fiber reinforcement.

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Moisture absorption increases the electrical resistance of CFRP in the fiber and transverse direction. In order to investigate the influence of deformation constraint on the electrical resistance increase, the electrical resistance changes of constrained and unconstrained CFRP specimens are measured in a furnace at constant humidity condition. The results show that the electrical change of the constrained specimen is smaller than that of the unconstrained specimen, and that implies swelling by moisture absorption affects the electrical resistant not only in the transverse direction but also in the fiber direction.

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In recent years, application of FRP (Fiber Reinforced Plastics) to the structure part material of a large-sized product is progressing quickly. To FRP, it is asked not only for tensile strength but also for compression strength and fatigue strength, and application for many large-sized structure products is considered. Under such a situation, the stitch fabric attracts attention as textiles for high performance composite materials instead of the fiber textiles used from the former (roving-crossing, chopped-mat). This paper presents the strength property of the fiber reinforced plastics using stitch fabric manufactured by VaRTM (Vacuum assisted Resin Transfer Molding) method.

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The effect of water on crack propagation resistance by fiber bridging of glass fiber reinforced plastic (GFRP) has been investigated. Specimens were immersed and weighed just before conducting the crack propagation test. Decrease of critical energy release rate by the water was measured as a function. The critical energy release rate of the matrix decreased with increase of the water absorption. The crack resistance of a bridged crack varied with the water absorption. To investigate the variation in the bridging mechanism under the water environment, we calculated the moisture concentration distribution on the cracked plane. As a result, the moisture concentration affected the crack propagation resistance. The increase of the moisture concentration caused the decrease of crack propagation resistance.

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