Technology for Spreading Tow and Its Application to Composite Materials

Abstract

In the previous paper, a new pneumatic method for spreading carbon tow was presented. In this paper, roll spreading method is investigated as the preliminary process of the pneumatic process.the results are as follows : (1) Tow is spreaded easily for smaller friction coefficient between roll and tow. Therefore tow can be more widely spreaded by fixed rolls than free rolls, because the static friction force acts on the fiver for a free roll and the kinetic friction force acts on the fivber for a fixed roll.(2) With an increase in tow tension, the spreaded tow width increases for a roll method, however, it is limited, because fiber breakage begins to occur at a higher tow tension.(3) When the number of fiber layers in the tow thickness direction decreases, the pressing force exerted on the fiber by the upper fibers reduces, then the rate of increase in spreaded tow width decreases. Therefore the spreading rate by a back roll becomes lower than by a front roll for the spreading process using the plural rolls.(4) Under the fixed total tow tension, the tension on the fibers located at the outer sides increases, while the tension on the fibers located at the center decreases with an increase in tow width. So the upper limit of tow width is determined by the condition that the tension on the fibers located at the center becomes zero.(5) Each fiber is removed from adhesion state of sizing by the roll method and the tow can be opened to some extent. So the roll method is effective as the preliminary process of the pneumatic method.