- 學位論文
外加磁場應用於導磁纖維射出成型產品穿透導電性影響之研究
Study of Through-Plane Conductivity of Injection Molded Parts by Applying Magnetic Field on Injection Molded Process Added with Magnetic Fiber
摘要
在各產業的快速變遷下，複合材料的應用日趨漸廣，其相關製程與技術儼然成為科技研發的重點項目，其中在纖維複合材料方面，由於纖維的配向和分佈會影響產品性能，因此如何控制其配向與分佈便成為關鍵之一。 本論文採用外加磁場應用於射出成型製程，借此控制鍍鎳碳纖維於熔膠充填時的配向行為。整體研究分為兩大部分，一為採用ANSYS®建立一對相吸的永久磁鐵，以不同間隔塊的材料和厚度，探討永久磁鐵在模具上磁場之分佈和衰減的情形，借此找出最適開模的配置。分析顯示模穴中的磁場，若用鐵作為間隔塊時會大幅下降，鋁則與無間隔塊時相當僅稍弱些。爾後根據實際開模建立與其相同配置之分析，並將實際量測的磁場分佈與分析值比對，發現兩者趨勢相同，因此其分析具有一定的可信度。最後再用與實際模具配置相同的分析，透過理論公式推演纖維在模穴內各角度和位置所受之磁矩，計算結果表示，纖維若在同一位置不同角度時，角度越靠近90˚磁矩越小;若為同一角度不同位置時，則需考慮該位置的磁通量密度，其絕對值越大者磁矩越強。 第二部分以LDPE混鍍鎳碳纖維搭配外加式磁場進行射出成型，利用不同料溫、模溫和射速探討成型參數於有無磁力下對纖維配向行為和穿透導電度的影響。實驗結果顯示，纖維配向張量於核心層時佔整體最低，最為靠近磁場方向，其次是剪切層和表皮層，且外加磁場者大多低於無外加磁場者。在料溫變化部分，其穿透導電度以高料溫220℃時為最佳比無外加者高出4.66倍。使用不同模溫時，以高模溫70℃外加磁場的纖維配向張量效果為最佳，其穿透導電度相較於30℃者改善了2.28倍。比較射速5%、15%和25%於外加磁場之結果，以最低射速5%之纖維配向張量最接近磁場方向，其穿透導電度相對於射速25%者，提高了3.01倍。
並列摘要
In the transition era of industries, the application of composite material becomes wider and wider. The related manufacturing process and technology have become focus of technology research and development. In fiber composite material, since contribution here sounds weird of fiber will affect product properties, how to control them is a key point to improve the properties. This paper uses an external magnetic field applied to injection molding process; this magnetic field controls the behavior of melt with nickel-coated carbon fiber during the filling. Overall study was divided into two parts. The first part was establishing a pair of permanent magnets which was modelled by ANSYS®. In order to find suitable mold layout, the simulation used different materials and thicknesses of spacing block to compare the magnetic field distribution and magnetic force reduction of permanent magnets on mold. The simulation showed that using iron spacing block substantially declined the magnetic force inside the cavity region. The result of using aluminum material was similar to the one without spacing block which yielded a little drop. After that, a real mold mode, referring to the simulation results, was established. Comparing simulation results and actual values, the trend were same.Therefore, the simulation has been confirmed to have a reliable credibility. Finally, using the mold layout simulation calculated magnetic moment at different positions and angles by theoretical formulas. The results indicated that when fibers were at the same position but different angles, it exhibited closer-to-90° fiber orientation and less magnetic moment. When fibers were at the same angle but different positions, it was necessary to check the magnetic flux density of that positions. The larger the absolute value of the magnetic moment, the stronger magnetic moment. The other part was experiment. It utilized LDPE mixed with nickel –coated carbon for injection molding assisted with external magnetic field. The study investigates behavior of fiber orientation and through-plane conductivity by different melt temperature, mold temperature, and injection speed with or without external magnetic field. The experimental results show that Fiber Orientation Tensor (FOT) at core is the lowest because it is close to the magnetic field and less influenced by the shear effect on the skin layer. Most FOT of the part with external magnetic field are lower than without one. Under various temperatures, the through-plane conductivity at high melt temperature of 200℃ is the best, it is higher than the one without external magnetic field 4.66 times. Using different mold temperature, the FOT at high mold temperature of 70℃ with external magnetic field is the best, and the through-plane conductivity is improved 2.28 times compared to the one at 30℃. Comparison of the results on 5%, 15% and 25% injection speeds with external magnetic field shows that the FOT at the lowest injection speed is the closest one to the magnetic direction, and the through-plane conductivity at 25% injection speed is enhanced 3.01 times.