Abstract
近年來由於產品性能的需求, 複合材料大量使用於航空太空, 機械及民生工業. 但由於其材料結構特殊(剛性,強度及耐磨耗懸殊之強化材與基材), 故加工時要求不同的加工技術條件. 由於材料本身的異質性與非等向性, 使得複合材料在切削上所面臨的問題與傳統金屬切削截然不同,截至目前複合材料的切削理論並未完整建立. 本論文將從正交切的觀點依序討論複合材料之切削機構, 切削力學及切削力預測.纖維排列方向為影響切削機構之最主要因素, 三種主要切削機構說明切削過程所經歷的破.挫曲破壞及脫層破壞說明沿纖維方向切削時切屑形成的模式. 垂直纖維方向則以彎曲破壞予以解釋. 任意角度之切削機構均可由以上三種機構加以綜合說明.針對切削機構所提出之三種主要切削模式, 吾人以樑理論, 複合材料力學及線彈性破裂力學為基礎, 針對不同切削模式進一步探討切削力與所產生切屑長度間之關係. 挫曲破壞的預測考慮積層樑之穩定, 脫層破壞的分析是基於線彈性破裂力學及能量平衡的考量, 彎曲破壞則是描述在破壞處之應力狀態. 理論預測值與實驗值相當吻合.切削力的預測以金屬切削理論為基礎, 擴展於非等向性之複合材料. 吾人以切屑負載(chipload) 為基礎, 並考慮複合材料沿不同纖維方向切時切削力特性不同. 比切削力是吾人首先獲得的重要結果, 比切削力可表示成切削參數及纖維方向的函數. 考慮瞬間位置之切屑負載, 利用比切削力的結果, 計算瞬間位置之主切削力與側切削力, 最後經簡單數學運算便可有效預測切削力, 實用性相當高.In recent years, customer requirements for increasingperformance have expedited the application of fiber-reinforecdcomposite materials, which posing new challenges tomanufacturing technology. Though the parts made of FRP majorlygain their forms in curing cycle, machining is necessary inprepreg shaping and product assembly. Besides, with the on-going development of three-dimensional FRP, the potential ofmachining as primary manufacturing process will increase. Theknowledge of cutting mechanism is indispensable in view ofcutting mechanics and machinability assessment in machining.The current study finds that fiber arrangement determines thethree principle cutting mechanisms:buckling,delamination andbending. Ananalytical model using beam theory,linear elasticfracture mechanics and composite mechanics to construct thecorrelation between cutting force and the produced chip lengthis presented. The author further proposes an orthotropic forceprediction model in milling of composite materials based onforce components from two fiber orientation considering thedirectional properties. Experimental results agree with theproposed model for unidirectionally reinforced carbon/PEEK. Amodified model considering general anisotropic force responseis developed for carbon/epoxy owing to fiber direction-dependent cut-damage affecting the accuracy of milling forceprediction. This investigation is expected to contribute towiden the application of high-performance fiber-reinforcedcomposite materials.