This review discusses the use of electrical resistance and potential change in various methods for monitoring Carbon Fiber Reinforced Plastic (CFRP) composites. CFRP composites have electrical conductivity as they contain carbon fibers. When fibers and fiber networks break within the structure its electrical resistance changes; the electrical resistance of carbon fiber changes with the applied strain just as physical resistance varies in a conventional strain gage. Using these changes in electrical resistance damage to CFRP composites can be monitored and applied strain measured without implementation of additional sensors. This makes CFRP a self-sensing material. The electrical resistance change method has been applied for decades to detect carbon fiber breakages. As regards the measurement of applied strain, there is divergence of opinion amongst researchers about the piezoresistance of CFRP. This discrepancy is discussed in detail in this review. For monitoring damage such as delamination cracks, the electrical resistance change method can accurately estimate the location and dimension of the damage. This review also discusses electrical potential change and eddy current methods for monitoring CFRP composites.

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An electromechanical model is proposed for predicting the resistance change in CFRP cross-ply laminates with transverse cracking loaded in tension. A one-dimensional equivalent circuit model was established for describing the relation between the resistance change and mechanical strain at a given transverse crack density. A shear lag model was employed for obtaining the mechanical strain distribution. The relative resistance change-strain curve was measured for various transverse crack density and the slope and secant of the curve were defined as the gage factor and residual resistance change, respectively. Unknown functions in the model were determined using the measured residual resistance changes. The model can predict the bilinear behavior in the relative resistance change-strain curves during loading/unloading. It is found that the second residual resistance change can be the parameter for predicting transverse crack density because it increases monotonically with transverse crack density compared with the gage factors.

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A thermally tempered glass has strong resistance for the surface crack, because the residual compressive stress exists near the surface of the glass. On the other hand, it also has the residual tensile stress in the center of the glass. Fracture behavior of the thermally tempered glass depends on the distribution of the residual stress. However, it is very difficult to clarify those relationships by an experiment. In this paper, the thermally tempered glass model using the Extended Distinct Element Method (EDEM) is proposed. Using our proposed model, the impact fracture behavior and the crack velocity are evaluated. From results for the normal glass and tempered glass, it is confirmed that the distribution of residual stresses can be evaluated by the thermally tempered glass model and the thermally tempered glass model is broken to many pieces by the residual tensile stress as well as experimental results. Furthermore, it is found that residual stresses of the tempered glass greatly influence the crack velocity.

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Deformation behavior in three-point bending test of Mo-Si-B alloy was investigated by recourse to finite element analysis (FEA) with microstructure incorporated. This Mo-Si-B alloy consists of hard, brittle T2 (Mo₅SiB₂) phase embedded in soft matrix of Mo solid solution. The sample contains pre-crack configuration at the middle in order to study the effect of the second phase (T2 particles) onto a crack tip during the bending test. Various optical micrographs were scanned, digitized and meshed for FEA. It was found that strain localization from the second phase at the crack tip was interfered with that from the loading pin in three-point bending test. Such interference could be reduced by replacement with end moment loading, in order to identify sole strain localization effect from the second phase at the crack tip.

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In thermal barrier coating (TBC) sprayed on the surface of high-temperature components in a land-based gas turbine (GT), stress is induced thermally or mechanically in the coating with the start-steady-stop operation of the GT. The coating stress leads to a crack initiation at the coating interface, and consequentially to TBC spallation. Thus, it is necessary to ascertain TBC interfacial strength, in order to assess precisely TBC spallation life. The aim of this study is to present the interfacial fracture toughness of TBC by using a TBC specimen exposed under a high-temperature environment. For accomplishing this, the fracture test is conducted using a mixed-mode interfacial fracture test device that has been proposed by our group. Thermal grown oxide (TGO) formation at the interface and residual stress of TBC, which are known as the origins of a reduction of the interfacial strength of TBC, also are examined. The intrinsic interfacial fracture toughness of TBC, which was estimated with the residual stress energy stored in TBC by thermal spray process, is related with cohesion of splat boundary and pore characterizing microstructure of TBC, in order to make clear why the TBC interfacial fracture toughness varied with exposure condition.

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To develop high strength glass ceramics, coal fly ashes produced by a power plant have been melted with addition of CaCO₃ and Na₂CO₃ to obtain glasses. Glass ceramics were produced by reheating selected glass mixtures in the region of 900-1200°C for 1 hour. The properties of the obtained glass ceramics were examined by XRD analysis, SEM observation, and material tests for strength, toughness, hardness, and chemical resistance. It was found that the glass ceramics produced by mixing CaCO₃ 20% and Na₂CO₃ 20% to the raw material have the best potentiality to serve as structural materials.

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An analytical method is derived for obtaining the in-plane static closed-form general solutions of thick curved beams with variable curvatures. The strain considering thickness-curvature effect is adopted to develop static governing equations. The governing equations are formulated as functions of the angle of tangent slope by introducing the coordinate system defined by the radius of centroidal axis and the angle of tangent slope. To solve the governing equations, one can define the fundamental geometric properties, such as the first and second moments of the arc length with respect to horizontal and vertical axes. As the radius is given, the fundamental geometric quantities can be calculated to obtain the static closed-form solutions of the axial force, shear force, bending moment, rotation angle, and displacement fields at any cross-section of curved beams. The closed-form solutions of the ellipse, parabola, and exponential spiral beams under various loading cases are presented. The results show the consistency in comparison with existed results.

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Al₂O₃-30%TiC composites doped with 0.5%MgO and 0.3-1.0% Y₂O₃ additives are pressureless-sintered at different conditions such as temperatures, soaking times, and heating rates under an argon atmosphere. The physical, mechanical properties, and cutting performance of sintered composites were compared with commercial one. In this work, the Al₂O₃-30%TiC composites doped with 0.5%MgO and 0.3%Y₂O₃ sintered at 1800°C obtained highest density of 97% of theoretical and flexural strength of 343 MPa. In addition, the cutting performance of the Al₂O₃-30%TiC-0.5%MgO-0.3%Y₂O₃ sintered at 1800°C was comparable with the commercial cutting tool.

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This study attempts to develop asymmetric ceramic membrane filter from nanosilica particles for ultrafiltration (UF) membrane. The alumina tube was used as a support and was coated with SiC which acted as an intermediate layer or microfiltration (MF) layer. The UF membrane was developed using the filtration technique through chemical suspension of the particles. Nanosilica was suspended in HCl acid, iso-propanol and acetone before it was deposited on the alumina tube using a special coating assembly. The membranes were characterised for pore size, thickness and microstructure. This study found that the use of nanoparticles for membrane development could easily control the pore size as well as the thickness of the membrane. The uniformity of the membrane thickness could also be achieved through this filtration technique.

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A method for estimating the fatigue life of wire ropes for elevators was developed. It is based on the assumption that the fatigue life of a wire rope is determined by the fretting-fatigue life of the wires from which the rope was made. Estimates done on a sample wire rope with this method are consistent with experimental measurements. The method of estimation involves four steps. First, a finite-element analysis is conducted to estimate the pressure between the wires. To take into account the behavior of the whole wire rope and each wire in the stress analysis, a zooming analysis is conducted. Second, a fretting-fatigue test on the wires is conducted to construct a fretting-fatigue database for them. Third, the fatigue life of each wire is estimated from the pressures between the wires and data from the fretting fatigue database. Finally, the fatigue life of the wire rope is estimated from the fretting-fatigue life of the individual wires. The rope's fatigue life estimated with this new method revealed some important findings: (1) the inner wires break earlier than the outer wires, and (2) the residual strength of the wire rope decreases rapidly after decreasing to 80% of the initial residual strength.

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An analytical solution to the flexural vibration problem during a nanomachining process using an atomic force microscope (AFM) cantilever is proposed in this paper. The modal superposition method was employed to analyze the response of an AFM subjected to a cutting force with an exciting force of an arbitrarily chosen frequency. The cutting forces were transformed into normal forces, distributed transversal-forces, and bending loading and acting on the end region of the AFM by means of the tip holder. Then, the effects of the axial force were used to solve the dynamic model. The analytical solution can be employed to evaluate vibration shape, model frequencies, and response histories of the cantilever with respect to different axial force effects and excitation frequencies. The results of this study reveal that the cutting force with a low axial effect and a moderately high excitation frequency are the best machining parameters for nanoscale processing using atomic force microscopy.

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