Research Abstract |
The research on reliability of Frm was carried out as described below, and it led to the useful results. 1) Tensile tests on several kinds of reinforcing ceramic fibers and its statistical analysis. 2) Tensile tests and their statistical analysis on boron fiber reinforced aluminum composites which are prepared in the study. 3) Computer simulation for tensile fracture of the composites. The results obtained are as follows; 1) The strength distribution of fibers can be expressed by multi-modal Weibull distribution. This distribution function gives appropriately the transition of the average strength and the coefficient of variation with the contact time of the fiber with liquid aluminium. Three kinds of defects, namely, inner, surface and reaction product, which are the initiation point of fracture, were observed by SEM. Finally, the defect due to the reaction product controlls the strength distribution when the reaction between fiber and matrix becomes very intenes. 2) Reliability of Frm
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is largely dependent of the statistical characteristics of the fiber strength and the fracture process of the composites. In the case of the non-cumulative fracture the strength distribution obeys the minimum value distribution of fiber strength, but the cumulative fracture process enhances the reliability of strength. 3) The results mentioned above were supported by monte-calro simulation technique using shear-lag theory. However, this theory cannot treat the normal stress of matrix along the axial direction, so that a problem remains for analyzing strictly the stress destribution. On the other hand, the cumulative distribution curve of strength was predicted by recursion analysis technique, which is a method of evaluating probabilistically the strength of unidirectional composites using the Weibull parameters of fiber obtained from tensile-testing. The results showed that the curve matched well with the Weibull plots of experimental data. 4) Furthermore, the present work suggests a new testing method to estimate the Weibull parameters on the condition that the fibers are embedded in matrix. Less
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