Technology for Spreading Tow and Its Application to Composite Materials

Part 3 : Spreading Mechanism of a New Pneumatic Method

Abstract

In order to investigate tow spreading mechanism by the new pneumatic method reported in the previous paper, spreading test using hung cylinders in air flow and observation of air flow through an array of fixed cylinders were conducted. The mechanism of tow spreading was discussed by comparing the results of these two model tests with experimental results of tow spreading.
The following results were obtained :
The pneumatic spreading force Fp and the recovering force fp act on a filament in an air flow at the same time. The position of the running filament in the pneumatic treatment is determined by the balance of the two forces F_p and f_p. Force F_p is influenced by the distance between two filaments and air velocity, while force f_p is determined by sagged length, filament diameter and air velocity. All the relationships between spreading width and processing conditions found in the previous experiments can be explained on the basis of the discussion above.
Air within tow is presumed to flow along the circumferential filament surface without so much disturbance. Therefore the significant local variation in the moved distance of the filament at higher flow rate is due to the local variation in the easiness of opening within tow.