碳纖維強化鋁基複材界面與機械性質之研究

Abstract

本實驗係以擠壓鑄造及纖維展開技術，製造碳纖維強化鋁基複材，並對複材進行熱處理，以研究複材界面反應物碳化鋁(Al4C3)成長機制和熱處理與碳纖維在基材中分散性對複材拉伸性質的影響。 實驗結果顯示，複材界面反應物 Al4C3的生成，並非均勻分布於碳纖維表面，而是在少數幾點不斷地成長。複材熱處理後，Al4C3的成長是具有特定方向，即在基面的a，b軸生長較快， 而在c軸方向則較慢。複材經熱處理後，因為界面反應物 Al4C3的數量增加且逐漸成長，導致複材在抗拉強度及延伸率均下降。本實驗採用纖維展開技術可讓碳纖維在基材內有較佳的分散性，使得碳纖與碳纖維之平均間距增大，此可減低已破裂碳纖維之應力集中，所以複材中裂縫成長發生的機率降低，故複材的最大抗拉強度，由未展開碳纖維複材的147.6MPa增為172.8MPa，纖維強度轉移率由未展開碳纖維複材的26.4%增為32.5%。

In this study the carbon fiber reinforced aluminium metal matrix composites were prepared by the squeeze casting and the technology of spreading fibers. The growth mechanism of the interfacial reaction products, aluminium carbide, and the effect of heat treatment and spread of carbon fibers in the matrix on the mechanical properties of carbon fiber reinforced aluminium matrix composites were investigated. The results showed that the interfacial reaction products, aluminium carbide, nucleated heterogeneously on the carbon fiber surface. After heat treatment, the growth of aluminium carbide was also anisotropic. It was faster in the a ,b axis of the basal plane than in the c axis. The degradation of the mechanical properties in composites was induced by the growth of aluminium carbide, after heat treatment. Because of using the spreading technology, the carbon fibers had a better distribution in the matrix. Since the average distance between the fibers is larger, the stress concentration caused by a failed fiber on other fibers decreases. The U.T.S of spread carbon fiber reinforced aluminium matrix composites was increased from 147.6MPa to 178.2MPa. By the same reason, the transformed coefficient of fiber strength (δ) of spread carbon fiber reinforced aluminium matrix composites was increased from 26.4% to 32.5% .