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Micro-injection molding of glass fiber reinforced parts
유리 섬유가 강화된 부품의 미세 사출 성형

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Authors
황순형
Advisor
윤재륜
Major
공과대학 재료공학부
Issue Date
2014-02
Publisher
서울대학교 대학원
Keywords
microinjection moldingfiber length distribution3D internal structurecompositesnumerical analysis
Description
학위논문 (석사)-- 서울대학교 대학원 : 재료공학부, 2014. 2. 윤재륜.
Abstract
Micro injection molding has recently gained tremendous attention owing to an increased demand for microelectromechanical systems (MEMS) and microsystems which encompass a wide range of industrial and engineering applications. Since the sizes of microinjection molded parts and devices are typically on the order of hundreds of micrometers, its flowability of molten polymer in a mold cavity becomes important to inject the molten polymers successively during the filling and packing stages during the injection molding. Particularly, the rheological properties of the injection molding materials play an important role in the flowability during an injection process due to the fact that the rheological properties are mainly affected by shear rate and temperature which are pragmatic approach to change injection molding conditions. The rheological properties affecting the flowability of molten polymers are extensively characterized by investigating fiber length distribution, volume fraction, and heat transfer of inclusions so as to determine the crucial parameters for the flowability inside micro-sized pitches and channels. Therefore, we firstly fabricated a thin tensile specimen and investigated the internal structures of the specimen by using Micro-CT to analyze the fiber length distribution of the samples. The data acquired by the Micro-CT was then processed by an image processing to analyze quantitative probability density functions, cumulative functions and probability functions. Also we compared it with several statistical fiber breakage models. From the fiber length distribution results, 3D internal structures of microinjection molded parts were obtained. The results of fiber orientation and flowability were compared with a numerical analysis by using a commercial software tool (MOLDFLOW). Both the experimental and numerical results indicated that long glass fibers, low volume fraction, and low thermal conductivity of inclusions show better flowability. Effective elastic modulus was measured and predicted by combining the theoretical modes.
Language
English
URI
https://hdl.handle.net/10371/123299
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College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of Materials Science and Engineering (재료공학부)Theses (Master's Degree_재료공학부)
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