高濃度短繊維含有樹脂のスリット状流路内の流れにおける繊維配向および速度・圧力分布の解析
Numerical Analysis of Fiber Orientation and Velocity Distribution in Slit Channel Flow of Concentrated Short Fiber Composites
加藤和典・張 佑新・大竹尚登
Kato, Kazunori / Zhang, Youxin / Otake, Naoto
The behavior of fibers in flow of concentrated short fiber composites is quite different from that in flow of dilute or semi-dilute suspensions. When fiber volume fraction is large, fiber-fiber interaction becomes very strong, and it introduces anisotropy in suspension structure and change in velocity distribution. When fiber length (l) is of the same order of cavity thickness (2H), fiber-wall interaction cannot be neglected.
In this paper, numerical analysis is used to calculate the fiber orientation distribution and to predict the melt flow in a slit channel cavity, in which the motion of each fiber is given from equilibrium conditions of forces in consideration with fiber-fiber interaction and fiber-wall interaction. Results are summarized as follows : (1) Distribution of fiber orientation and melt flow becomes approximately steady after a flow distance of X = 20〜30 mm (2H = 2mm). Pressure gradient decreases gradually with temperature increase due to shear heating. (2) Fiber-wall interaction makes fibers shift away from the mold wall and concentrate at ξ/l = 1/2 (ξ: distance from the mold wall). The peak of fiber orientation distribution is made at (θ, φ) = (90°, 165°). (3) As flow rate increases, shear heating concentrates in a layer of low fiber volume fraction near the mold wall, and the pressure gradient decreases. As the fiber length increases, the thickness of the low fiber volume fraction layer increases. This causes pressure gradient decrease. (4) As the fiber-fiber interaction parameter nl3 (n : fiber number density) increases, the melt flow approximately becomes a plug one.
Key words: Short fiber-polymer melt composite / Slit channel flow / Fiber-wall interaction / Fiber orientation distribution / Velocity distribution