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Stitching is an effective method for improving interlaminar strength. Another advantage of stitching is the ease of stacking fabrics for large-scale structures. Stitching leads to the ease of quality control. Although there are many studies on through-thickness stitching, the characteristics of composites consisting of stitched unit layers have not been sufficiently studied. In this paper, the fatigue process for composites consisting of stitched unit layers was discussed. UD (unidirectional) and DBM (double-bias mat) laminates were used as specimens. Fatigue damage was continuously observed by the replica method at two stress ratios, namely, tension–tension and tension–compression loadings. The fatigue damage of the UD laminate was initiated from stitches, 90° strands and resin-rich regions. The propagation of the damage was affected by the stress ratio, and we considered that compressive load tends to cause delamination. In the case of the DBM laminate, the first sign of damage was that delamination almost occurred and was observed near stitches and resin-rich regions. Transverse cracks were formed by delamination. The damage process for the DBM laminate is almost independent of stress ratio.

Glass Fiber Reinforced Plastics (GFRP) have been applied to products such as building components and various structural materials in industrial plants due to their excellent lightness and corrosion resistance, as well as weather resistance since the 1980's. Use of GFRP for large-scaled components and/or components with repetitive load has increasingly widespread in recent years, and both tensile and compressive properties have thus become important. Reinforcing laminate for GFRP has been mainly woven fabric such as glass woven roving due to its easy handling. However, its fiber winding and gap occurrence have been problems to be solved. In the recent years, new fiber fabrics for reinforcement have come on the market owing to rapid development of weaving machine, and one of the new fabrics is the stitched fabric. This glass fiber stitched fabric has been increasingly developed in Europe and all over the world for over ten years, and in Japan, has extended its application for ship for about ten years. This study investigates and examines GFRP reinforced with unidirectional glass fiber stitched fabric, in respects of the effect of fiber laminated constitution, fiber content and fiber diameter on tensile and compressive properties. Additionally, this study also examines relevance between weaving patter of fiber and strength property by comparing 0 degree/ 90 degree stitched fabric with GFRP with general woven roving.

Tension–tension and tension–compression fatigue tests were carried out for a DBM (double-bias mat) laminated composite. The composite is composed of stitched unit layers. The effect of stitching is considered to be complicated. Thus, the fatigue process was observed by a replica method at certain periods, and the fatigue mechanism of different stress ratios was discussed. It is found that the fatigue damage of DBM is mainly delamination induced by stitching. The fatigue damage is observed independently of stress ratio. In the meantime, stitching has a favorable effect. It is considered that stitching increases the momentum of inertia of the layer and compressive strength. Therefore, the effect of stitching is discussed considering the trade-off mechanism of the adverse and favorable effects mentioned above.

The application of ceramic components in gas turbine engines enables the improvement of the power output and the efficiency of gas turbines by increasing the turbine inlet temperature. The high temperature properties of the ceramic materials offer the potential of higher turbine operating temperatures with no cooling techniques and therefore the ceramic components with higher temperature limits are becoming more attractive. In this study, the ceramic turbine wheel is applied in the aircraft gas turbine engine and the engine testing is demonstrated under full load operating conditions. The successful testing of the ceramic turbine components in the aircraft gas turbine engine has been accomplished. The test results indicate that the ceramic turbine wheel is capable of operating under the high thermal shock condition of fast starting to full speed. Furthermore, the adoption of some new ceramic turbine design concepts is proposed in actual use for aircraft ceramic turbine engines.

In Japan, all large capacity fossil-fuel power plants are supercritical units and a steam condition of 24.1 MPag, 538/566°C has been adopted. Through extensive development work, the design and material technologies for steam turbines with a 593°C steam temperature have been established, and the steam condition of 24.1 MPag, 538/593°C was applied to the 700 MW steam turbine of Hekinan No. 3 Unit, Chubu Electric Power Co., Inc. for the first time in Japan. This unit has been operating successfully since it started commercial operation in April, 1993. Mitsubishi Heavy Industries, Ltd. (MHI) designed 1000 MW class turbines with more advanced steam conditions of 600°C class main steam and reheat steam temperatures for the first time in Japan, applying the latest technologies developed for 600°C class application.

In actual components, almost all creep failures occur at a stress concentrated parts. Therefore, the cavitation during creep in a notched bar was examined both by using FEM and actual testing on notched CrMoV-steel bar specimens, which were heat-treated in advance so as to get the creep-embrittlement in a rather short time. The change of creep voids in their number, distribution, orientation and coarescing direction in the notch root region was made clear by using SEM and an image processor. It was found that the cavitation behavior corresponded well with the creep damage based on the maximum principal stress.

In recent years, the turbine inlet temperature becomes higher and higher to grow up the power of gas turbine engines in recent years. So hot section parts, such as combustor and turbine, are generally designed as cooling structures made of heat resistant metals. On the other hand, the high temperature properties of the ceramic materials offer the potential of higher turbine operating temperatures with no cooling techniques and therefore the ceramic components with higher temperature limits are becoming more attractive. In this study, the ceramic turbine is applied in the aircraft gas turbine engine. For gas turbine engines, tight fit configuration is generally taken for the joint structure between a ceramic turbine and a metal shaft, and its constrain force transmits the drive torque and withstands the thrust force acted on the turbine. Since the constrain force is decreased due to the difference of the thermal expansion rate between ceramic and metal at the high temperature condition, the initial constrain force should be taken large enough considering the decrease of the constrain force. But if the fit is too tight, the ceramic turbine will be cracked at the jointing process. So an optimization is necessary to balance these

Microstructural degradation in two kinds of sintered silicon nitride due to high temperature exposure was examined on specimens after flexure static fatigue tests and room-temperature flexure tests of heated specimens. Surface oxidation layer was formed due to the reaction of silica formed by the oxidation of β-Si3N4 and sintering additives segregating from the interior grain boundary phase. Corresponding to the oxidation layer, a degraded layer containing numerous micro-pores resulting from the segregation of the sintering additives was formed just beneath the surface oxidation layer. The thickness of the surface oxidation layer, which was measured nondestructively by means of X-ray diffraction method, had increased along with the heating. Consequently, the room temperature strength of specimens after heating was considered to be related to the thicknesses of surface oxidation layer and surface degraded layer.