| Summary: | 碩士 === 國立清華大學 === 動力機械工程學系 === 100 === The purpose of this thesis is to research a carbon fiber epoxy composite material plate which contains crack, in the condition of different temperature on two sides, the phenomenon of crack stress concentration cause by the thermal diffusion in opening mode; we used the stress rounding factor to derive the stress intensity factor, and understand the behavior of the area around the crack tip. The thesis can be applied to the shell machine such as the aircrafts and the ships, when the outside temperature of the shell is smaller than the inside temperature of the shell, and there is a crack form on the outside shell, we analyzed three kinds of the crack length and two kinds of fibers direction, so there are total six different situations. In these six situations, we analyze the difference of the distributions of temperature by thermal diffusion, the distributions of y direction thermal stress and the stress intensity factors. We assume that the direction of the fibers in the plate is perpendicular or parallel to the crack and analyze it. In order to be close to the real geometry situation of crack tip and use the equation of stress rounding factor, we use a curve which has a 0.5mm radius on the crack tip to simulate. It takes time for thermal diffusion, so the time become an important parameter; therefore this thesis use transient analysis, to research the situation of different temperature fields at the different time, the variation of stress intensity factor according to the condition of fibers direction which are parallel or perpendicular to the crack and the condition of the different crack length. Finally, we found that in the condition of the three kinds of crack length and two kinds of fibers direction, the stress intensity factors will all become greater as the time increases. At the situation of same fibers direction and the same time, the longer the crack is, the greater the stress intensity factor is. When the direction of crack is x axis, the fibers direction are y axis, the y direction stress on the blunt crack tip will be greater than the y direction stress on the blunt crack tip at the situation of same time and same crack length and the fibers direction are z axis. But, for the corresponding crack, the stress intensity factor showed the opposite tendency.
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