應用流體展開器三維內流場之數值分析與實驗發展碳纖維流體展開系統

Abstract

本研究中, 吾人利用數值模擬及碳纖維展開實驗成功地發展了一部高效能碳纖維氣體展開床, 並將碳纖維紗束以 1:1的氣體展開器在各種不同條件下進行展開實驗, 且於實驗中利用攝影技術記錄纖維展開過程, 基於本研究歸納所得結果如下: 1. 本文成功地應用遠場邊界條件於纖維氣體展開器之三維網格，探討內流場之流動形態；並利用有限體積法結合k-ε紊流模式求解三維不可壓縮之雷諾平均納維爾-史托克氏 (Reynolds-averaged Naiver-Stokes RANS) 方程式；且將纖維氣體展開器於不同的工作壓力條件下, 以速度及壓力分佈分析內流場的流動形態並進行探討, 最後將計算數值與實驗量測結果比較,結果發現定性上有相同的趨勢, 且在定量上得到相當符合的結果,證明此三維流場的分析可應用於纖維氣體展開器之設計。 2. 本研究成功地設計一高效能碳纖維展開系統, 並定義了新的變數-展開均勻度, 用於說明碳纖維紗束在氣體展開過程中分散均勻的程度, 藉此變數展開的碳纖維可做一定量的比較; 並可容易的獲得纖維展開的最佳工作條件。此外, 由計算的模擬及展開實驗, 我們可瞭解碳纖維分散的機制及纖維與氣流交互作用的行為。 3. 為了證明藉由氣體展開製程可克服碳纖維紗束不均勻鍍層的結果, 將碳纖維紗束分為展開與未展開兩組, 比較無電鍍鎳後的結果。結果證明展開的碳纖維紗束可被覆均勻的金屬鎳; 且鎳鍍層厚度可低於0.2 µm。這是首次金屬鎳可均勻度著於紗束內所有纖維表面; 且藉氣體展開系統可克服製程表面處理不均的問題。

In this study, a high efficient carbon fiber tow pneumatic spreading system was successfully developed by means of numerical simulation and carbon fiber spreading experiment. Carbon fiber tow was spread on 1:1-scale model of the pneumatic spreader at various conditions, and photography techniques were simultaneously used to record the procedures of fibers spread. Based on the investigation, some results can be summarized as follows: 1. The three-dimensional numerical analysis was carried out on incompressible fluid flows by using finite volume method combined with the k-εturbulence model which solves Reynolds-averaged Naiver-Stokes equations. Comparisons of numerical results with measured velocity and pressure distributions were made, and a good agreement was found in both qualitative and quantitative analysis. The performance was better than prior studies in one-dimensional orifice formulation. Agreement among those results validated the assumptions inherent to the computational calculation and gave confidence to more complex geometries as well as flow fields. 2. The work successfully designs a high efficient carbon fiber pneumatic spreading system. A new variable, spreading evenness, was defined to specify the dispersing extent of fibers in a carbon fiber tow during the fiber pneumatic spreading process. By the spreading evenness, a quantitative comparison of a spread carbon fiber tow can be made and the optimum condition can be easily obtained at fiber spreading experiments. Also, by the computational modeling and the spreading experiment, both the dispersing mechanism of carbon fibers and the interaction between the fibers and the airflow were understood. 3. To identify the non-uniform coating in a carbon fiber tow can be overcome by the pneumatic spreading process; two groups of spread and unspread carbon fiber tow coated with nickel by electroless plating were compared. The results showed that a uniform Ni coating could be obtained on each fiber in the spread carbon fiber tow, and the thickness of the Ni film could be coated on carbon fiber tow less than 0.2 µm, and it’s the first time the Ni thin film can uniformly be coated on the fiber surface in the overall fibers.