2000 Fiscal Year Final Research Report Summary
Dimensional stability and Residual Stresses on Fiber-Reinforced Aluminum Composites
| Project/Area Number |
10650107
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Materials/Mechanics of materials
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| Research Institution | Niihama National College of Technology |
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Principal Investigator |
IKEUCHI Yasukazu Niihama National College of Technology, Materials Science and Engineering, Professor, 材料工学科, 教授 (20044092)
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| Project Period (FY) |
1998 – 2000
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| Keywords | Composite / Fiber-reinforeed metals / Residual stress / Thermal expansion / X-ray diffraction / Aluminum alloy / Alumina fiber / SiC fiber |
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| Research Abstract |
Residual stresses arise in fiber-reinforced metal matrix composites after cooling down from elevated temperatures due to the thermal expansion mismatch between the matrix and fibers. The thermally induced residual stresses were measured by the X-ray method for two types of composites with small fibers (α-Al_2O_3/Al-1%Li γ-Al_2O_3/Al. γ-Al_2O_3/Al-5%Cu) and with large fibers (SiC_<CVD>/6061Al). Results of the X-ray triaxial stress analysis showed that the stress state in the matrix sampled by the X-ray beam was biaxial on the composite with large fibers. whereas triaxial on the composites with small fibers. The thermal residual stress was dependent on the matrix materials as well as a thermal history of the composites, and was found to satisfy a condition of stress equilibrium between the matrix and the fibers in the composites. The residual stress parallel to the fibers was the maximum principal stress for all of the tested composites. The thermal expansion behavior along the fiber dir
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ection of γ-Al_2O_3/Al and γAl_2O_3/Al-5%Cu composites was studied in a temperature range of 300-800K.A strain hysteresis loop attributable to the presence of thermally induced residual stresses in the composites was observed on both composites. During cooling the composites from 800K to 300K.the matrix was plastically deformed in tension. With subsequent heating of the composites. the tensile matrix stress elastically decreased to zero stress level and then the matrix ws plastically deformed in compression. During thermal cycling of the composites. the lastic manner of the Al-5%Cu matrix was observed to be somewhat complex as compared to that of the pure Al matrix. Time-dependent strain during isothermal holding of the γ-Al_2O_3/Al composite at elevated temperatures was revealed. The Change in strain of the composite under isothermal conditions was influenced by the sign of residual stresses. The relaxation behavior of the matrix residual stress during isothermal holding of the composite could be well described in a form of the power law for steady-state creep of pure aluminum. Less
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