The present study deals with the compressive strengths of low density woods (balsa, redwood) and rubber at two levels of strain rates including impact range. Within impact range of strain rate of the order of 10 ^2(s<-1>), we used a weight drop tester, where the strains and the stresses of specimen were measured by acceleration sensor in order toknow the stress and deformation behaviour, and to recognize the strain rate dependency of the stress-strain relations. These data will be available when the present materials are used as a shock-absober.

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A single-fiber pull-out model composite for an aramid/epoxy system was specially designed to measure the stress distribution of an aramid fiber embedded in the matrix using micro-Raman spectroscopy. The stress transfer length of the fiber was about 300μm. Stress distribution of the fiber changed after the fiber/matrix interfacial debonding and the fiber axial stress showed the maximum at a certain point in the debonded region, which was larger than the applied pull-out stress. As the applied stress was decreased gradually after the debonding, this larger stress peak was considered to be caused by the holding of the previous stress by the fiber/matrix interfacial friction.

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In this paper, the shear deformation behavior in the interface between the plastic and the fiber is described. we tried two load type test by using the boron fiber embedded in a plastic resin which had diameter 14mm. One is the pull out test method and another is the push out one. The main conclusion obtained by the present study is shown as follows. The relationship between the shearing force and the shearing deformation has the velocity dependence. The separate fracture of the interface begins by the maximum shearing load. The difference of the test method doesn't influence the maximum shearing force. It was found that the main bond strength between the fiber and the plastic resin was the dynamic friction force.

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In order to develop metal composites reinforced by vapor grown carbon fibers (VGCF) with an average diameter of 150nm and aspect ratio of 10-500,porous VGCF-carbon (C) preforms were fabricated by carbonizing VGCF-phenol resin (PF) compacts. If the VGCF/PF compacts were carbonized at 3000℃ for 3600s in argon gas atmosphere, two or three dimensional VGCF networks highly connected by carbon were formed in VGCF/C performs with 19.3-38.2vol% VGCF and 44.9-76.5vol% void. The VGCF/C preforms achieved an excellent balance of high thermal conductivity of 0.407W/cm・K and low electrical resistivity of 0.003Ω・・cm at room temperature which are higher than thermal conductivity of titanium (0.20W/cm・K) and lower than volume resistivity of carbon black (about 0.01Ω・cm). VGCF content dependence of thermal conductivity and volume resistivity of the VGCF/C preforms were discussed through perfection of network structure.

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Effect of thermal and hydrothermal environment on residual stress in carbon/epoxy composites was studied. Raman spectroscopy was used to monitor the fiber residual stress in single fiber composites specimens, which were exposed to air at 80℃ and immersed in water at 25℃ and 80℃ for 24hours. As a result of immersion in water at 80℃ and drying, the residual compressive stress build-up was observed. This increase in the fiber compressive stress can be explained by the change of viscoelastic properties of matrix during in heated water above the glass transition temperature of matrix and it was also observed that no stress region existed form the fiber end to 1mm length in heated air at 80℃.

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In order to clarify S-N properties of carbon fiber, fatigue tests were investigated over a range of stress ratio, R, from 0.1 to 0.7Hz. The carbon fibers used were standard T300 fibers produced from polyacrylonitrile precursors by Toray Industries, Japan. It was found that the S-N properties of the carbon fibers clearly show the fatigue behavior, depending on the stress ratio R. It was also found that fatigue strength of carbon fiber is governed by two parameters such as the maximum stress σ_<max> and the stress amplitude σ_a, and that the combined stress parameter σ_<max>^<1-α>×σ_a^α is useful to describe the fatigue strength behaviors of the different stress ratios. Mirror-mist-hackle features were clearly observed on the fracture surface of specimens. It was confirmed that the relation σ_<max>・A^<1/4>=const. holds between the mirror or mist area, A, and the maximum stress, σ_<max>.

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A tangent delta of a polymeric material, which influences the vibration damping capacity strongly, is high in value nearby the glass transition temperature of the material. Therefore, when the constituents of a polymer-based composite material are various in their glass transition temperatures, the magnitude of the macroscopic tangent delta of such a composite is expected to be high in wider range in temperature. In the present study, a shape memory polymer (SMP) particle/SMP matrix is used as a sample material and its macroscopic complex modulus and tangent delta are derived explicitly by using the equivalent inclusion method and the Mori-Tanaka's theorem. For the case of a four mode type of distribution of the glass transition temperatures of particles, the value of the macroscopic tangent delta becomes higher than that of the monolithic SMP at any temperature and it becomes constant in the temperature range from 20℃ to 60℃.

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Fatigue life prediction of a symmetric cross-ply carbon/epoxy laminate subjected to cyclic loading in the 0° fiber direction is attempted on a ply-by-ply basis. First, tension-tension fatigue tests on the cross-ply laminate under constant amplitude cycling at room and high temperatures are performed. The normalized S-N relationship for the cross-ply laminate using the fatigue strength ratio agrees with that for the unidirectional laminate made of the same prepreg tape. This indicates that the fatigue behavior of the cross-ply laminate in the fiber direction is substantially governed by that of the constituent 0° plies in the laminate. Second, under the assumption that the damage and failure of the 90° plies in the laminate occur at an early stage of life and the final failure of the laminate is determined by the failure of the 0° plies, a simple fatigue failure model for the cross-ply laminate is developed on the basis of the classical lamination theory and the ply fatigue model considering the in-situ static strengths. The proposed fatigue model with a consideration of the in-situ strength of ply succeeds in adequately predicting the fatigue strength of the symmetric cross-ply laminate for the fiber direction, in spite of ignoring effects of the stress redistribution in the laminate due to the local damage and failure of the 90° plies during constant amplitude fatigue loading.

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Braided fabric is one of the textiles which have long history, and in present it has been applied to the reinforcement for composite materials. The most interesting characteristic of braided fabric is variable braiding angle, which is a design parameter of composite materials. In this study, the influence of the braiding angle on bending property of CFRP braided composite pipe was evaluated. In the bending tests, although bending modulus was almost same irrespective of the braiding angle, CFRP pipe with the braiding angle of 30 degrees showed longer fracture deflection than ones with the braiding angle, CFRP pipe with the braiding angle of 30 degrees showed longer fracture deflection than ones with the braiding angle of 45 and 60 degrees.

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Actual FRP structural components used on ships, aircrafts and so on have large thickness in order to increase rigidity and strength. Although normally such thick composite materials are made of stacked thin lamina like cloth, they need a number of stacking process in order to achieve certain thickness. On the other hand, knitted fabrics have lower rigidity and strength than woven fabrics, but have larger thickness due to them specific loop structure. Then in this study, knitted fabrics were integrated with woven fabrics, and the thick composite material which has both high mechanical properties and large thickness was manufactured, and evaluated the bending property.

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The more structure becomes large, the more the thickness of the material which constitutes structure also increases. The increment of the thickness of material means the increment of the laminate, and the stress states become more complicated. Therefore it is hard to compare thick and multilayered composite materials and thin ones simply. In this study, the bending property of thick composite material was clarified from the view point of the fracture mechanism based on the microscopic observation. Especially the resin having high fracture toughness was applied to the thick composite, in order to consider the effect on the interlaminar delamination.

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The ultrasonic shot peening is being popularized among aeronautic industries for production parts and maintenance application because of its compact equipment that allows processing partially and that can be integrated into production line. However, the ultrasonic shot peening has a big difference in processing method compared to that of conventional shot peening. Therefore, the peening management, which influences the peening effect, needs to be renewed. In this report, processing conditions as shot amount and injecting distance, are set as management items. Then the most suitable condition is experimented by intensity and full coverage time obtained from the management above. The applications are also studied using parts, such as gears and springs, and confirmed its quality after processing. As a result of study and experiment, the ultrasonic shot peening has an outstanding peening effect.

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The authors investigated the surface refined characteristics and fatigue strength of NH materials treated by Double Shot Peening (DSP) and Stress Double Shot Peening (SDSP). The results oblation : (1) High hardness of 383HV by DSP (2) Large maximum compressive residual stress with -733MPa of the NH+DSP material (3) Increased fatigue limit of the NH+DSP material. 33%(stress ratio R=0) and 28% (R=-1) higher fatigue limit than the NH materials, respectively. And considerably increased fatigue limit of the NH+SDSP material. 58% (stress ratio R=0) and 39% (R=-1) higher fatigue limit than the NH materials, respectively. (4) There is proportionality relation between mean stress and amplitude stress is R=0. However, there is no it in R=-1.

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