Papers by Author: Toshio Ogasawara

Abstract: Reusable spacecraft/supersonic aircraft is research and development towards the realization of a new aerospace transportation system.Because these transport aircraft is to flight at a speed of more than Mach 5,are considering the use of scramjet engine.Because this engine uses air as an oxidant and liquid hydrogen as a fuel,the combustion gas temperature is more than 2500°C.So the combustor is required lightweight material and super-heat-resistant material.In the field of aerospace,SiC-based ceramics that is heat-resistant materials are well known as to maintain the mechanical properties at high temperatures and have a high oxidation resistance.However, this material limit as heat-resistant material is about 1600 °C .Therefore, it can not be used in an environment of scramjet engine combustor.There are the measures by metal structure to be force-cooled by refrigerant fuel,but apply is difficult because the system is complexity and very heavy. In this study use the hafnium-based super heat-resistant ceramics that is having a melting point more than 2000°C. Purpose is to develop a new technique for forming the ceramics mainly composed from Hafnium Carbide (Melting point:3950°C) that is very high melting point and have oxidation resistance by melt impregnation to inside C/C composite.In addition, implement the evaluation of changes in the organization after each process by the cross-sectional observation and strength assessment by three-point bending test.

Abstract: C-and BN-interphases on SiC fibers for unidirectional SiC_f/SiC composites were formed by EPD process, and their microstructure and mechanical properties were investigated. Whereas the C-SiC_f/SiC composites showed a pseudo-ductile fracture behavior with large amount of fiber pullout, the BN-SiC_f/SiC composites fractured in a brittle manner without fiber pullout in spite of sufficient thickness of BN interphase. It is inferred from the results of EDS that sintering additives would react with h-BN-interphase, and the interphase did not act effectively for toughening the SiC_f/SiC composites.

Abstract: In this study, poly (ether ether ketone) /carbon nanotubes (CNTs) nano composites were fabricated by using multi-walled carbon nanotubes (MWNTs) as the filler. Tensile properties of nano composites at before and after glass transmission temperature were studied. At room temperature, the addition of 15 wt% MWNTs increased the tensile modulus (0.1
0.3% strain) by 89% and the yield stress by 19%. At after glass transmission temperature (200) , they increased by 163% and 42%, respectively. The experimental results showed that the reinforcement of CNTs are more effective for high temperature than room temperature. DMA results showed an increase in storage modulus with increasing MWNTs loading fraction at both below and above the glass transition temperature Tg (around 145oC). Scanning electron microscope and transmission electron microscope images showed that the MWNTs were well dispersed in the matrix and orientated one direction.

Abstract: TriA-PI is a newly developed phenylethnyl terminated polyimide. It exhibits excellent mechanical properties and processability with high glass transition temperature (Tg>300°C). Nano-size particles of fullerene were dispersed throughout a thermosetting polyimide Triple API (TriA-PI) to elevate the glass transition temperature. The increase of the glass transition temperature of the composites with the fullerene was confirmed by dynamic mechanical analysis (DMA).