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평판형 die내를 흐르는 단섬유 현탁계의 섬유배향과 압출팽창에 관한 수치해석
A Numerical Analysis on the Fiber Orientation and Die Swell of the Fiber Suspensions in Slit Dies
HWAHAK KONGHAK, August 1993, 31(4), 430-438(9), NONE
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Abstract
섬유현탁액이 평판형 압출성형 die내를 흐를 때, die의 기하학적인 형태와 초기유입배향상태가 섬유배향상태와 압출팽창비에 미치는 영향에 관해서 유한요소법을 사용하여 수치해석하였다. 섬유입자의 배향상태는 배향텐서의 개념을 사용하여 해석하였고, 섬유입자간의 상호영향을 고려하였다. 백면근처의 섬유입자는 초기유입배향상태에 관계없이 축방향으로 정렬이 되어가는 경향을 보였고, 중심선상에 놓인 섬유입자는 초기유입배향상태를 그대로 유지하였다. 팽창 및 수축형 도입부를 가진 die를 사용하면 초기유입배향상태의 조절이 가능하다는 것을 수치해석 결과 확인할 수 있었다. 섬유입자간의 상호영향을 나타내는 인자인 CI값이 증가함에 따라 섬유입자의 정렬상태는 흐트러지며 압출팽창비는 증가한다. 압출팽창비는 die의 L/D가 증가할수록 팽창평판 die의 경우 감소하였고, 수축평판 die의 경우 증가하였다. 또 정렬된 초기유입배향상태일 때의 압출팽창비가 임의배향의 초기유입배향 상태일 때의 그것보다 작았다.
The effects of the geometrical shape of extrusion dies and the fiber orientation at the entrance on fiber orientation and die swell were analyzed numerically by finite element method. The fiber orientation and the interaction among the fibers were analyzed by way of the orientation tensors. The fibers near the die wall aligned along the flow direction regardless of its initial orientation. But the fibers near the center line retained its initial orientation. It was verified that the use of extrusion dies of contraction or expansion entrance made it possible to control the fiber orientation significantly. The CI value which represents the interaction among fibers also affects the orientation and the die swell. The orientation disturbed and the swell ratio increased as the CI increases. The swell ratio decreased in expansion die but increased in contraction die as the L/D ratio increases. The swell ratio when fibers were introducted as aligned state was smaller than the case of randomly introduced state.
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