- 學位論文
微裂縫滲水結冰對複合材料負載能力之影響
The effect of freezing ice on the loading capacity of fiber composite plates containing a microcrack
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摘要
本文將探討一含邊緣裂縫之碳纖維環氧樹脂複合材料平板，當水氣沿著裂縫滲透入平板後，結冰體積膨脹而導致裂縫前端附近應力集中的現象，另外會探討裂縫周圍各角度的應力，還有溫度低於攝氏零度下後，因熱膨脹係數不同造成的應力，以及結冰體積膨脹受到限制的情況，透過有限元素套裝軟體ANSYS來進行本文的模擬和分析，並利用滑順因子推導不同裂縫尺寸時的應力強度因子。 結果顯示，裂縫長度越長，應力場越大，在y走向纖維複材中裂縫長度對應力場的影響較明顯。在裂縫前端，纖維y走向所得之應力強度因子比纖維z走向所得之應力強度因子大。纖維方向為y走向之模型,裂縫尖端的應力場下降的斜率較纖維z走向大。而當溫度降至攝氏零度以下所產生之應力遠小於結冰時所產生之應力，可忽略其影響。若結冰膨脹位移受限，在裂縫接近複材邊緣的情況下，應力值將大幅提升。若裂縫位置靠近複材中央，應力值雖有上升但不明顯。
並列摘要
This thesis is on the carbon/epoxy composite plates containing a microcrack, which traps in water. When temperature is at freezing point, the volume of water will expand and cause stress concentration at the tip of the crack. The stresses at the different angle around the tip of crack are analyzed, and the condition that the temperature is below 0° Celsius is also considered. The simulation and analysis of this study have been done with ANSYS, and the stress intensity factors have been calculated by using the stress rounding factor. The results show that the longer crack causes the greater the stress. It is also found that the crack length affect more to stress field when fiber orientation in y direction. For the same crack size, the stress intensity factors are greater for the y-direction fiber than for z-direction fiber. The stress gradient near the tip of the crack descends more for y-direction fiber composites than for z-direction-fiber composites. When the temperature is below 0° Celsius, the stresses are far smaller than those at 0° Celsius. In the situation that the freezing ice is well contained in the composite plate, for the crack being near the edge of the plate, the stress increases dramatically. While the crack is near the center of the plate, the stress is slightly larger than that a edge-crack plate.
參考文獻
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