Semisolid metal exists when strip was solidified from molten at the high speed roll casting. Some of the defects of roll cast strip were formed at semisolid condition. Surface crack and alligator crack at inside are typical defects which occur at semisolid condition. In this paper, elimination of the surface crack on 5182 aluminum alloy strip was investigated by a single roll caster equipped with a scraper which was originally proposed.

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This paper deals with modeling of granule collapse in a spherical powder compact during cold isostatic pressing (CIP). To obtain the radial stress distribution in the compact under an isostatic pressure, we newly formulate an ordinary differential equation for radial displacement when Young's modulus is given as a function of radial coordinate. The equation is solved numerically, and we actually obtain the radial stress distribution during CIP. By substituting the stress distribution into fracture location theory, we derive the joint probability density of granule collapse as a function of the radial coordinate and the applied CIP pressure. For a given parameters, we estimate the collapse probability of granules in the powder compact during CIP.

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The in-situ formation mechanism of nano-scale AlN particles on the surface of pure Al powder by direct nitridation and mechanical properties of resultant P/M Al-AlN composite were investigated. Nano-scale AlN particles were formed on the powder surface by heat treatment at 873 K in N_2-H_2 mixed gas. The mean particle size of AlN was estimated as about 40-80 nm by TEM observation. Yield strength (YS) and ultimate tensile strength (UTS) of P/M extruded Al-AlN composites powder increased with increasing AlN content. On the other hand, the elongation of Al-AlN composites slightly decreased. Increment of UTS of P/M extruded Al-AlN materials was larger compared to that of YS, suggesting that the work hardening of Al-AlN composite was improved by AlN dispersion strengthening.

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Dependence of the mechanical properties of P/M extruded material of titanium with the silicon nitride (Si_3N_4) on solid phase decomposition of Si_3N_4 was investigated. Si_3N_4 particles within Ti composite powder were decomposed during the spark plasma sintering at 1223 K with 30 MPa pressure for 3.6 ks, and then, nitrogen and silicon atoms originated in Si_3N_4 were defused into titanium matrix. The extruded of Ti-1.0 mass% Si_3N_4 powder material had ultimate tensile strength (UTS): 1139 MPa, and yield stress (0.2% YS): 1065MPa. UTS and 0.2%YS of P/M extruded material of Ti with 1.0 mass% Si_3N_4 were 2 and 2.5 times compared to extruded pure Ti powder material, respectively. It was considered that the solid solution strengthening of both nitrogen and silicon originated in Si_3N_4 caused high strength of P/M extruded material of Ti with 1.0 mass% Si_3N_4.

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Recently, with the aim of low cost and high cycle "out-of-autoclave method" is proposed. However, since out-of-autoclave method of forming a vacuum pressure, imperfect moldings such as voids are likely to occur. Therefore, compared to the autoclave method, it is quite inferior in terms of the molding quality. In the past, the smart manufacturing technique has been studies to perform efficient molding by forecasting the molding state using the numerical simulation based on the information obtained by monitoring the molding process. But there is a problem that the modeling quality is degraded by the sensors embedded in the interlaminar of CFRP. In this study, by using data assimilation technique to integrate the forecast value by numerical simulation with the observed value by measurement, we constructed the model state estimation technique with high accuracy and we proposed that the technique of estimating the internal state of CFRP without embedding a sensor. In this technique, we estimate the whole internal temperature distribution of CFRP from observed values of the surface of CFRP by using an ensemble kalman filter, which is one of data assimilation techniques. In addition, we confirmed that the thermal conductivity distribution could be estimated simultaneously.

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VaRTM process impregnates resin to fiber preform using difference in pressure between atmosphere and vacuum, and attracts attention as a method to mold FRP at relatively low cost. However, resin impregnation behavior in the fiber preform is not understood exactly, and the formation of voids during the process is a problem to be avoided. It is said that a distribution medium which is incorporated on the fiber preform as a surface layer has a significant effect on resin impregnation behavior. In this study, multipoint measurements for resin flow during VaRTM process are carried out by using embedded fibre optic sensors. By simultaneously infusing epoxy resin into two glass fibre preforms with or without a distribution medium that are separated by a plastic film, resin amount impregnated through in-plane flow and out-of-plane flow via the distribution medium are compared. It has been found that resin amount impregnated through the out-of-plane flow via the distribution medium is found to be dominant, especially for thinner fiber preform. In addition, numerical calculation for resin impregnation during the VaRTM process was also carried out. The simulated resin amount impregnated via the distribution medium agreed well with the experimental results.

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During VaRTM (Vacuum assisted Resin Transfer Molding) a distribution medium which is incorporated on fiber preform as a surface layer is used to shorten impregnation time of resin by increasing the flow rate of resin and is removed after molding. In this study, the distribution medium is replaced by a thermoplastic polyamide mesh, and the mesh is still remained in the fiber preform after VaRTM process. The mesh is expected not only to improve the resin flow but also to suppress impact damage in the composite laminates after molding. Multipoint measurements for resin flow during VaRTM process are carried out by using embedded fibre optic sensors. It is confirmed that the polyamide mesh inserted in the fiber preform increased the flow rate during the impregnation of resin. Drop weight impact tests have been found that impact responses are improved and interlaminar delamination in GFRP laminates is suppressed by inserting the polyamide mesh. From these results it is shown that improvements in both resin flow and impact damage suppression can be achieved by the single action of inserting the polyamide mesh.

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In general, it was considered that mechanical properties of FRP should be same if reinforcing fiber and matrix, reinforcements and surface treatment were same whatever molding method was, however it was revealed that mechanical properties were influenced by molding method. In this study, four kinds of GFRP with different surface treatment and molding pressure were molded by resin transfer molding and static tensile property and crack propagation behavior were investigated. It was found that the decrease in the tensile modulus had relation to the interface properties due to the surface treatment, but didn't have relation to the molding pressure. Whereas, the crack propagation was restrained by higher molding pressure when the interface properties were low.

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Purpose of this study is to investigate the fracture mechanisms of shoulder part of composite pressure vessels subjected to impact loading. CFRP laminates simulating shoulder part of composite pressure vessels were fabricated by filament winding (FW) followed by vacuum assisted rein transfer molding (VaRTM) process, and an impact test were conducted on the specimen. A tensile test was also conducted on the specimen impacted to evaluate damage tolerance. The result suggests that the major impact damage for composite laminates occurred mainly in the matrix region, such as splittings. In some specimens fiber fracture were also observed. The tensile strength was obviously reduced by the application of impact.

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In the present study, long term durability of the candidate material for the next radio astronomy satellite under space environment were investigated. The materials were high modulus PAN based carbon fiber reinforced polycyanate ester and epoxy. In order to simulate the space environment, thermal cycle tests between -197 and 120 ℃ were conducted. Surface observations and bending modulus measurements were also conducted. Transverse cracks in 90 ° plies were observed at 1 cycle and the number of crack increased with cycles. Bending modulus, however remain constant during thermal cycles. Microscopic damage in carbon fiber reinforced polycyanate ester was suppressed at the late stage of the thermal cycle. This result indicated the long term durability for carbon fiber reinforced polycyanate ester was superior.

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Degradation rate of bioabsorbable polymer is affected by molecular weight and crystallinity. In this study, effect of thermal treatment on biodegradation of poly (lactic acid) (PLA) was investigated. Annealing was conducted on PLA specimen. Annealing temperature was selected as 70 ℃ and 130 ℃. Three types of specimens is used ; non-annealing, 70℃-annealing, 130℃-annealing. Crystallinity was also measured. Immersion tests were conducted to measure weight change of the specimen. Crystallinity increased with annealing temperature. Water absorption of the specimen annealed was smaller than that of non-annealing specimen, because the specimen with higher crystallinity has less space which water molecular invade. Young's moduli for the non-annealing and 70℃-annealing specimens were close, whereas the 130℃-annealing specimen was larger because of increasing deformation resistance due to increasing crystallinity. Fracture strength for the non-annealing and 70℃-annealing specimens were also close, however strength for the 130℃-annealing specimen was much smaller because of embrittlement due to successive crystallization.

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Micro-Braiding technique is an effective method to impregnate resin to carbon fiber yarn. In this study, we investigated the resin impregnation of textile composite using micro-braiding technique experimentally and analytically. The consolidation experiments are conducted on the plain woven fabrics made of micro-braided yarn composed of carbon fiber yarns (3K and 6K) and thermoplastics fiber yarns (polyamide) under some molding conditions in order to reveal the impregnation behavior. Good correlation was obtained between the experiments and analytical predictions. This result indicated that the analysis proposed are effective to predict resin impregnation behavior.

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Porous aluminum (Al) was fabricated by a tool-traversing friction powder sintering process. In this process, a mixture of Al powder and sodium chloride (NaCl) powder as spacer particles was used as a starting material. The powder mixture was placed in a mold, compaction and sintering of the mixture was conducted only by the traversing of a rotating tool as in friction stir welding. In this study, functionally graded porous aluminum was fabricated by a tool-traversing friction powder sintering process which had different range of porosity of 60%, 70% and 80%. By X-ray computing tomography observation, it was found that the fabricated functionally graded porous Al had uniform pore distribution in each porosity range. By compression tests, it was shown that the plateau stress was decreased with the increased in porosity. Consequently, it was shown that compression properties of functionally graded porous Al can be controlled by volume fraction of NaCl.

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SLIM (Smart Lander for Investigating Moon) is a midget lunar explorer that is designed to substantiate several new techniques for pinpoint landing. The traditional large-scale and complex landing gears using crash-honeycomb are unsuitable in the SLIM explorer due to it is required to reduce the size and weight. Previous studies have shown that the new type of landing gears using porous aluminum have sufficient energy absorption. However, the energy absorption for uniaxial compression is not always most appropriate design of landing gears, thus it is necessary to evaluate mechanical properties to similar load to the practical application other than compressive force due to appropriate design. In this study, relationship between the mechanical property and the strain rate were investigated, thorough compressive, indentation and punching test with closed-cell porous aluminum ALPORAS.

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Porous aluminum has lightweight and high energy absorption properties. Therefore, it is expected to be used as structural materials. In this study, sandwich panel consisting of A6061-ADC12 functionally graded porous Al and A1050 Al plate was fabricated by friction stir processing (FSP) route. It was shown that obtained sandwich panel has different pore structures by a difference of holding time during foaming process.

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Fatigue test of Inconel 718 was conducted at high temperature (923K) using compact tension specimens. Microstructures of the longitudinal cross section of the fractured specimens were observed together with the fracture surfaces. Fatigue test at room temperature and creep test at high temperature were also conducted for the comparison. It has been verified that the intergranular fracture mode was predominant at high temperature whether the fracture was due to creep or creep-fatigue. However, at room temperature, the fatigue fracture mode was transgranular. Furthermore, microcracks which is almost perpendicular to the main crack were observed in the specimens fractured by creep or creep-fatigue. Oxidation at the grain boundaries at creep-fatigue condition was not verified by the EPMA analysis.

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To measure the deformation of the structural material, an irradiated grid or grating fabrication method has been developed. Using a laser projector, squire grid or parallel grating was irradiated to the specimen that has luminous or photochromic paint on the surface. After ten minutes irradiation, a grid or grating can be observed of bright and dark parts. Bright parts were irradiated by laser beam and can be observed in 1 minute. 3-point bending test was performed after ten minutes irradiation of laser, and grid could be observed during 3-point bending test.

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The full-field principle strains are the most important parameters for instability evaluation. In this study, the microscale principle strain distributions of a carbon fiber reinforced plastic (CFRP) specimen under a three-point bending load were studied using the scanning electron microscope (SEM) moire fringes. The normal strain distributions in the horizontal and the vertical directions, and the shear strain distribution were first measured with the SEM moire method. The maximum as well as the minimum principle strain distributions and their orientation distributions were then determined from the theoritical strain status analysis. The principle strains are not affected by the specimen grating, even if the specimen grating direction is not parallel to the specimen axial direction.

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