Research On Spreading Technology In Preparation Of Prepreg For Automated Fiber Placement By Hot-melt Method

The preparation technology of prepreg by hot-melt method is significant to the automated fiber placement(AFP) and the low-cost manufacturing technology of advanced composites. The width and its stability are key properties of prepreg, and it is also the key point and difficult point of preparation technology by hot-melt method. In order to research the spreading process, this paper has researched that:(1) Based on the classical hot-melt method, the overall plan to produce prepreg for AFP was designed and verified by experiment. Meanwhile, the control systems of unreeling tension, rolling tension and prepreg operation speed were designed.(2) In order to eliminate the instability of width and perfect the preparation process of prepreg, the post-spreading process was studied by building the experiment system. The result shows that: by roller spreading method, the prepreg after post-spreading has better width stability and edge quality, as well as the appearance quality than squeeze method. By heating the spreading roller, the resin would has better fluidity, which could make the resin equally distributed on the surface of prepreg.(3) With the help of high-speed digital image sensor, the spreading process of the fiber bundle by the rods or rollers in zig-zag fashion under different processing parameter was analyzed. The results indicate that the rod has much stronger effect on spreading fiber bundle than roller. By increasing the fiber tension or wrap angle as well as decreasing the distance between the adjacent rod and roller, the fiber bundle can be spread wider. Furthermore, the spread width of the fiber bundle increases when the fiber operation speed rises from 1m/min to 5m/min. And there is no distinct change in spreading width when the operation speed continues to increase. However, the excessive fiber tension will lead to an unstable spreading process, which could cause the bundle separating and fiber breaking.(4) In order to research the effect of impregnation process on the spreading quality of prepreg, the impregnation process of prepreg and its influence factors were analyzed. And the influences of these factors such as the heating temperature of resin on the width and its stability of prepreg were studied by orthogonal experiment. Finally, the rank among these factors as well as the best combination of these factors to improve the width and its stability were obtained, which provide the reliable basis for the research on the preparation process of prepreg.