Mesoscopic Contact Behavior between Carbon Tows and Round Roller

Textile composites have been widely used in aerospace, automotive, shipbuilding and construction fields due to their high specific strength, high specific modulus and high designability. Preform is the reinforced skeleton of textile composites, and tows, as the basic unit of preform, lose up to 5%~30% of its mechanical properties due to friction, compression and bending in the process of weaving and forming. Among them, the mechanical properties loss rate due to friction is as high as 9%~12%. However, researchers have conducted the friction and wear behavior of tows using different methods, the contact mechanism of tows in the process of friction and wear is still unclear. Different forming conditions of preforms will result in different contact surface morphology of tows, which seriously affects the mechanical property of preforms. Therefore, it is necessary for the study of friction mechanism to explore the contact mechanism between carbon tows and round roller. The contact area of tows is determined by the contact behavior of numerous fibers. Researchers have carried out a sea of research on the arrangement mode and mechanical properties of fiber in tows, but the quantitative relationship between the arrangement mode of fiber and the contact area of tows is rarely studied. In order to improve the prediction accuracy of tow's contact area, a self-designed experiment device was used in this paper. Combined with the thin film indentation method, three-dimension (3D) surface morphology of the contact surface of tows was analyzed, and the effect of different pre-tension and contact angle on the contact area between carbon tows and round roller was studied. In consideration of fiber orientation, the theoretical prediction model of the contact area between carbon tows and round roll was established. Experimental value, Hertz model and modified model were analyzed by the test of significance. The results showed that the orientation of tows in the contact surface was a key factor of the contact area. When the contact angle increased from 60° to 170°, the orientation of tows decreased gradually, the contact area between carbon tows and round roller decreased gradually, and the contact area at the contact angle of 60° was 22 times than 170°. When pre-tension increased from 0.19 N to 1.47 N, the orientation of tows increased gradually, the contact area between carbon tows and round roller increased gradually, and the contact area at the pre-tension of 1.47 N was about twice than 0.19 N. According to the probability of significance testing, the modified model could accurately predict the contact area between carbon tows and round roller. And it deemed friction behavior of tows should be studied by using the contact model considering the orientation of fiber in tows. As a key factor affecting the friction and wear behavior of the tows, the contact area of the tows was significant for the forming of composite materials. However, the contact behavior of tows and round roll was the result of the comprehensive influence of various factors. In this paper, the influence of different pre-tension and contact angle on the contact of tows was merely analyzed. In the future, the diameter of round roller, the roughness of the friction pair and the physical properties of tows will be discussed to further reveal the friction and wear mechanism of tows.