Key Engineering Materials Vols. 345-346

Abstract: Carbon nanofiller reinforced PLA was fabricated, and the mechanical properties and heat resistivity were measured. Vapor grown carbon fiber (VGCF) produced by Showa Denko K.K. was used for reinforcement, which has 150 nm in diameter and 10 μm in length. No surface treatment of VGCF was conducted. VGCF and PLA were compounded by using a twin screw extrusion machine and then pelletized. The weight fraction of VGCF ranged from 1wt% to 10wt%. Three point bending specimens were fabricated by using injection molding. At first, three point bending tests were carried out at room temperature. The bending stiffness increased from 3GPa to as high as 5GPa, but the bending strength slightly decreased. SEM observation of the fracture surfaces indicated pull-out of VGCFs over the fracture surfaces. These results imply that adhesion between VGCF and matrix was imperfect. Then, the heat deflection temperatures and glass transition temperatures of the specimens were measured. The addition of VGCF did not increase the glass transition temperature but slightly increased the heat deflection temperature.

Abstract: Silicon carbide fiber-reinforced silicon carbide matrix composites (SiCf/SiC composites) are attractive materials for use in the blankets and divertors of fusion reactors due to their excellent thermo-mechanical properties and inherently low induced radioactivation. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture impose a severe limitation on the practical applications of SiC materials. SiCf/SiC composites can be considered as a promising candidate in various structural materials, because of their good fracture toughness. In this composite system, the direction of SiC fiber will give an effect to the mechanical properties such as fracture toughness and tensile strength. Therefore, it is important to control a proper direction of SiC fiber for the fabrication of high performance SiCf/SiC composites. .

Abstract: The transparent ITO multi-layers films were fabricated on quartz glass substrate by colloid dip-coating technique from indium metal ingots and stannic chloride. It was systematically studied that the effect of the electrical properties of the ITO on doped Sn in quantitative change, different dip-coating technological conditions such as thermal treatment process, coating number plies by four-probe instrument. From the 5 wt. % Sn to 20 wt. % Sn, with the amount of doped Sn increasing, the sheet resistance of ITO was up to minimum and then increased. Sintering temperature and holding time were the reasons for the electrical properties of the ITO films, when other parameters are unaltered. It is also concluded that coating number plies was play an important role on electrical properties of ITO films by sheet resistance. From the results of research, it can be seen that the multi-layer films has optimum characteristics, whose sheet resistance is 117'/□, when the use level of Sn is 10%wt,heated in 800°C 15min with repeated dip-coating seven times..

Abstract: The wings of a dragonfly have many complicated structures. The configuration of the costal vein of the wings of a dragonfly is different from them of other insects. So, we paid attention to the configuration of the costal vein of the wings in this study. In order to know the functions and structures of the wings of a dragonfly, several 3-D models of the wing of Anotogaster Sieboldii were created, and calculated with the 3-D finite element method. In addition, we created a 3-D model of the wing of Hybris Subjacens which has the configuration of original wing, and compared the models of Anotogaster Sieboldii and Hybris Subjacens. As a result, it was clarified that the arch configuration of the costal vein controls the bending and the torsion of the wings.

Abstract: Biological soft tissues like muscles and cartilages are anisotropic, inhomogeneous, and nearly incompressible. The incompressible material behavior may lead to some difficulties in numerical simulation, such as volumetric locking and solution divergence. Mixed u-P formulations can be used to overcome incompressible material problems. The hyperelastic materials can be used to describe the biological skeletal muscle behavior. In this study, experiments are conducted to obtain the stress-strain behavior of a solid silicone rubber tube. It is used to emulate the skeletal muscle tensile behavior. The stress-strain behavior of silicone is compared with that of muscles. A commercial finite element analysis package ABAQUS is used to simulate the stress-strain behavior of silicone rubber. Results show that mixed u-P formulations with hyperelastic material model can be used to successfully simulate the muscle material behavior. Such an analysis can be used to simulate and analyze other soft tissues that show similar behavior.

Abstract: The innovative method based on prefabricated fiber laminate composites bonded to lightweight precast panel was applied for quality control of RC strengthening members. The experimental investigations for this method were presented for flexural member. Three different groups such as control group without strengthening, conventional fiber bonding group and innovated PFLC group bonded to precast panel. Tested results showed good or better capacities comparing to conventional strengthening method for flexural members. This investigation indicate that good enhancement with respect to quality control and reliability can be possible by the installation and epoxy injection with prefabricated panel using fiber laminate composites.

Abstract: In recent years, as the robot technology is developed, the researches on the artificial muscle actuator that enables robot to move dexterously like biological organ become active. Actuators are one of the key technologies underpinning robotics. Particularly breakthroughs of power-to-weight ratio or energy-density in actuator technology have significant impacts upon the design and the control of robotic systems. The widely used materials for artificial muscle are the shape memory alloy and electro-active polymer. These actuators have the higher energy density than the electromechanical actuators such as the electric motor. However, there are some drawbacks because these actuators have the hysteretic dynamic characteristics. In this paper, the segment control for reducing the hysteresis of SMA is proposed and the simulation of an anthropomorphic robotic hand is performed using ADAMS. A new approach to design and control of SMA actuators is presented. SMA wire is divided into many segments and their thermal states are controlled individually in a binary manner(ON/OFF). The basic experiment for evaluating the dynamic characteristics of SMA wire actuator is performed.

Abstract: The present study was undertaken to examine the effects of metal coatings at the surfaces of diamonds impregnated in metal bond matrices. Diamonds with or without coatings were incorporated into same bond matrix to form two metal-diamond composites in order to reveal the effects of coatings. Diamonds with same coatings were applied to three bond matrices to check the influences of matrix properties on the effects of coatings. The transverse rupture strength (TRS) of the composites was measured to ssess their mechanical behavior. Circular sawing was also conducted to reveal the contribution of coatings to diamond retention. SEM was used to analyze the fractured surfaces of the composites. For same bond matrix, the coatings at diamonds were found to increase the TRS of the composites. However, it is difficult to compare the effects of coatings in different bond systems.

Abstract: Carbon nanotubes (CNTs) have been the subject of intensive studies for applications in the fields of nanotechnologies in recent years due to their superior mechanical, electric, optical and electronic properties. Because of their high Young’s modulus (≈ 1 TPa), tensile strength (≈ 200 GPa) and high elongation (10-30%) as well as high chemical stability, CNTs are considered to be attractive reinforcement materials for light weight and high strength metal matrix composites. In this paper, we described a scheme for multi-scale modeling for the elastic and plastic properties of CNT/metal nanocomposites using the numerical analyses of the three-dimensional finite element method based on the continuum mechanics of a unit cell. In particular, the quantitative effects of the distribution and the array of the CNT reinforcement (viz. cross-over, vertical and horizontal distributions) on the elasticity and plasticity of the nanocomposites were investigated and the anisotropic characteristics of elasticity and plasticity of the nanocomposites were linked with the extremely high aspect ratio of CNTs.