In this paper, conventional analysis and control methods on open- and closed-loop system of disturbance attenuation control in water-wave tank, is extended to consider variation in bottom surface geometry by additionally locating a submerged block. Frequency responses obtained by experiment and analyzed by the boundary element method (BEM) show good agreement in low frequency range, for various changes in block height, width, and position. Specifically, resonant frequencies are almost identical only with 2%error. The resonant frequency is decreased when the block height and width becomes larger. It is shown that the desired performance to attenuate standing-wave oscillation is provided by H_∞ control system design considering bottom shapes. Control experiment shows that sinusoidal disturbance with 1st to 3rd resonant frequencies are attenuated up to 40%, and random disturbance is attenuated up to 30% at 1st to 3rd resonant frequencies.

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Piezoelectricity and shape-memory are the two smart properties which have been widely and separately used in many fields. In this research, a new kind of nano composite is prepared to combine these two smart properties in one kind of material. Most composites of piezoelectric materials and shape-memory materials are made by bonding multiple layers in different materials, however, the interface between layers usually become the weak point because of the poor combination of different kinds of materials. In view of this problem, the new composite is made of lead zirconate titanate (PZT) nano particles and shape-memory polyurethane (PU). It is a great challenge to disperse high weight density particles (PZT) homogeneously in low weight density solvent (PU dissolved in tetrahydrofuran) without chemically surface modification on particles. Another challenge is how to keep the two smart properties well after compounding the new composite. This new composite is produced by mixing PZT particles and PU in tetrahydrofuran, casting and hot-press. The Field Emission Scanning Electron Microscope (FE-SEM) images of this new composite containing 60% (weight percent) PZT show the well dispersion of the PZT nano particles in PU. The experiment results show that this new composite has very strong shape-memory property and piezoelectricity. Taking advantages of two smart properties in one material, this new composite has the promising potential to be developed into self-sensing material. With the advantage of PZT particles, this new composite can be utilized as actuators and sensors in nanofabrication. It also can be made into devices in different shapes to be applied in different conditions according to PU's flexibility.

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Nanocomposites of polyphenylene sulfide (PPS) were prepared with a benzimidazolium surfactant used as organic modification for the montmorillonite (MMT) by melt blending. The benzimidazolium-modifided MMT( Bz-MMT) exhibited a large interlayer spacing of 3.26 nm and showed a high thermal stability compared to the commonly used clay modified by alkyl ammonium salts(DK-1N). The morphology of the polyphenylene sulfide (PPS)/Bz-MMT nanocomposites were evaluated by X-ray diffraction (XRD) and transmission electron microscope (TEM). The results showed good overall dispersion of the MMT in PPS matrix. Thermogravimetric analysis (TGA) were used to evaluate the thermal properties of polymer/clay nanocomposites. The results of TGA showed the thermal stability of the polymer/clay nanocomposits was enhanced.

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Carbon fiber reinforced plastics (CFRP) having both high strength and lightness has been widely used in various fields, however, the delamination failure is the major problem. Since the 3D textile CFRP has a unique mechanical properties such as good peeling resistance and high toughness, it has aroused a number of advantages. For the easy weaving and cost performance 2.5D textile will be also worth in applications. Meanwhile, the feature of the carbon fiber with excellent electrical conductivity and electromagnetic shielding performance was considered to be used as an electromagnetic shield material. Thus, the electromagnetic shielding performance of 3D fabric structure CFRP is investigated for improving electromagnetic shielding effect. The carbon fiber woven fabric was designed for this new multi-layer structure in an efficient vacuum assisted resin transfer molding (VARTM) process to produce a carbon fiber woven composites. The mechanical properties and electromagnetic shielding performance were discussed.

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This study examines the interlaminar shear strength and the self-healing of spread carbon fiber/epoxy laminates containing graphene oxide. Healing is accomplished by incorporating a microencapsulated healing agent and a catalyst within an epoxy matrix. Self-healing is demonstrated on short beam shear specimens and healing efficiency was evaluated by the strain energies of virgin and healed specimens. The damaged area of the specimens was also examined by an optical microscope.

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The objective of the present study was to analyze the stress distribution of ceramics die for a deep drawing by varying the die radius parameter. In this study, using VHX-2000 microscope to observe the crack line of the ceramics die and using FEM software to simulate the stress distribution on the die surface. Accordingly, the optimum die fillet radius parameter can be performed to optimal process design.

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In this work, the influence of processing condition on relative density and mechanical properties of specimens prepared by Selective Laser Melting (SLM) technique using 18-Ni maraging steel powder was investigated. The results show that it is necessary to control laser energy density of about 65-80 J/mm^3 to obtain SLM specimens with relative density higher than 99.9%. In addition, it was confirmed that mechanical properties of dense SLM specimens were less influenced by building direction on the base plate.

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Criteria for macroscopic failure in glassy polymers are discussed. The modified Tresca and modified von Mises laws for shear flow are examined in relation with the morphology of shear band based on the experimental results shown in literatures. Several problems remaining to be solved are noted on some parameters included in these laws. The current criteria for craze formation are examined with particular respect to dilatational stress component. They are clearly denied by our criterion, which asserts the craze formation as a cooperative process of shear flow and fibril elongation in localized region. The experiments under different conditions are required to examine the validity of our criterion.

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The crazing behavior of polystyrene (PS) was investigated in ethanol for examining failure criteria. The pure shear and uniaxial tension were applied to PS plate specimen in ethanol at room temperature. Only crazing was identified on the specimen surface under both stress states. Crazes were formed at lower stress in ethanol than in air. This was supposed to be caused by plasticization effect of ethanol. For confirming the plasticization effect, differential scanning calorimetry (DSC) was conducted. The glass transition temperature of the ethanol-absorbed PS specimen was greatly lowered to about 40℃. The newly proposed criterion gave the theoretical critical stress ratio being almost consistent with experiment.

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Failure behavior of polycarbonate(PC) under pure shear and uniaxial tension was investigated in air and ethanol at room temperature. Shear flow with shear bands was observed in air, and craze formation was confirmed in ethanol. The critical stress for craze formation in ethanol was lower than the shear flow in air. The shear flow was revealed to occur obeying the modified Tresca criterion. The craze formation in ethanol was shown to obey our criterion, in which simultaneous elongation and shear flow were supposed to occur in craze formation process.

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In this study, bending and transverse shear properties of plain weave fabric composite laminates are investigated through the finite element analysis considering the intra-lamina inhomogeneity due to the weave architecture of constituent yarns. Using the homogenization method, the effective Reissner-Mindlin plate stiffness of the composite laminate is calculated. Then, the effect of the number of plies on the laminate bending elastic modulus and the transverse shear modulus is evaluated. For the bending property, the experimental evaluation is also conducted to validate the numerical analysis. Through the numerical and experimental investigations, it is found that in case the number of plies is large (eight-plies or more), these moduli are constant independent of the number of plies, however in case the number of plies is very small (three-plies or less), these moduli significantly decrease.

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In this paper, effect of kinking damage on tensile fracture behavior of poly-p-phenylene benzobisoxazole (PBO) fiber was investigated in monofilament tests. Kinking damages was created on surface of virgin fiber by winding bundle fibers to steel rod. Diameter of steel rod was set to 5, 2.5, 1.25 and 0.65 mm. Kinking damage density was defined to evaluate occurrence of kinking damage owing to bundle fiber was wound onto the steel rod. The fracture surface was observed using Scanning Electron Microscope (SEM). It was found that the tensile strength of fiber with kinking damage was well fitted the Weibull distribution function with 2 parameters. The tensile strength of PBO fiber with kinking damage was explained in the concept of the effective volume. It was shown that the crack growth of PBO fiber with kinking damage developed along the kinking damage.

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Sandwich structure has high damping properties when viscoelastic materials are used as a core layer. Damping properties and bending stiffness were able to be improved by changing the structures of core layer or surface layers. A hybrid pattern with series and/or parallel model was designed, and their role in bending stiffness was clarified. Combining with the orientation of carbon fiber at the surface layers, we can effectively design damping property. Thus, these new design concepts for improving both damping and stiffness are expected to be used in the design of CFRP sandwich structures.

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For the characterization and defect detection of carbon fiber reinforced composite materials, Ultrasonic Testing is one of several commonly used nondestructive examination techniques for its sensitivity and accuracy. However, owing to the complicated interactions among fibers, delamination, randomly distributed voids, and the ultrasonic wave propagation, the detailed effect mechanisms of the above internal damage on wave propagation and material properties haven't been clarified. Thus, our work is dedicated to the detailed effect mechanism of void and delamination on ultrasonic wave propagation and the dynamic mechanical properties, for giving guidance on the development of high-precision ultrasonic testing technology.

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