Study of Through-Plane Conductivity of Injection Molded Parts by Applying Magnetic Field on Injection Molded Process Added with Magnetic Fiber

• Main Authors: Ya-Lin Tseng, 曾雅麟
• Other Authors: Shia-Chung Chen
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/77nk26

碩士 === 中原大學 === 機械工程研究所 === 103 === 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.