Friction Dynamics in Mechanical Bar Spreading for Unidirectional Thin-Ply Carbon Fiber
Topic(s) : Manufacturing
Co-authors :
Ehshan UL-HAQ (NETHERLANDS), Marie HONDEKYN (BELGIUM), Onur YUKSEL (NETHERLANDS), Clemens DRANSFELD , Baris CAGLAR (NETHERLANDS)Abstract :
Thin-ply carbon fiber reinforced polymers (CFRP) offer a promising pathway to overcome the limitations of traditional composite materials, delivering improvements in first-ply / first-damage criteria, fatigue life, and ultimate strength [1]. Typically characterized by individual plies with a thickness below 0.100 mm, these composites leverage size effects and design flexibility, facilitating smaller pitch angles at specific thicknesses [2,3,4].
Diverse techniques for producing unidirectional thin plies include airflow spreading, ultrasonic vibration, and mechanical methods [5]. Mechanical bar tow spreading, a method involving controlled tension to pull dry tows through bars or pins, is exemplified by a lab-scale tow spreading line depicted in Figure 1, developed at TU Delft, featuring static, reconfigurable spreader bars and tension sensors.
This work introduces an experimental framework to systematically assess and quantify the influence of various mechanisms on the friction behavior of carbon fiber during mechanical bar spreading. By examining the interplay of wrap angle, tow pre-tension, relative velocity, local tension, and roving width, the objective is to provide valuable insights into the friction behavior of carbon fibers in mechanical manufacturing processes and how the friction behavior deviates from what the Capstan equation predicts [6]. Aligned with the overarching goal of advancing thin-ply composites for improved mechanical performance and design versatility, our proposed framework contributes to the optimization of the mechanical spreading process.
Data has been collected of the mentioned parameters, using the custom lab-scale tow spreading line (fig. 1). Intriguingly, the findings deviate from the established Capstan equation, shown in equation 1 [6].
= ln(T2/T1)/(Σɸ). (1)
The results indicate that increased roving pre-tension T1 leads to a reduced apparent friction coefficient μ during bar tow spreading, as is demonstrated in Figure 2. As the pre-tension T1 increases for a given wrap angle ɸ, the measured tension-ratio T2/T1 decreases.
It is expected that this effect arises due to the mechanical deformation that the tow undergoes as tension varies. This departure from conventional friction dynamics in this context provides crucial insights into carbon fiber tow spreading as dependency in contact pressure, tow width, and slip rate could be deconvoluted. Building on these findings, we propose a novel method for determining the friction of a roving through a spreader bar system that accounts for the effects of pulling speed, pre-tension, (a)symmetricity of the local wrap angles etc., and thus leading to a higher fidelity of the resulting microstructure of unidirectional thin-ply carbon fiber [7].
Diverse techniques for producing unidirectional thin plies include airflow spreading, ultrasonic vibration, and mechanical methods [5]. Mechanical bar tow spreading, a method involving controlled tension to pull dry tows through bars or pins, is exemplified by a lab-scale tow spreading line depicted in Figure 1, developed at TU Delft, featuring static, reconfigurable spreader bars and tension sensors.
This work introduces an experimental framework to systematically assess and quantify the influence of various mechanisms on the friction behavior of carbon fiber during mechanical bar spreading. By examining the interplay of wrap angle, tow pre-tension, relative velocity, local tension, and roving width, the objective is to provide valuable insights into the friction behavior of carbon fibers in mechanical manufacturing processes and how the friction behavior deviates from what the Capstan equation predicts [6]. Aligned with the overarching goal of advancing thin-ply composites for improved mechanical performance and design versatility, our proposed framework contributes to the optimization of the mechanical spreading process.
Data has been collected of the mentioned parameters, using the custom lab-scale tow spreading line (fig. 1). Intriguingly, the findings deviate from the established Capstan equation, shown in equation 1 [6].
= ln(T2/T1)/(Σɸ). (1)
The results indicate that increased roving pre-tension T1 leads to a reduced apparent friction coefficient μ during bar tow spreading, as is demonstrated in Figure 2. As the pre-tension T1 increases for a given wrap angle ɸ, the measured tension-ratio T2/T1 decreases.
It is expected that this effect arises due to the mechanical deformation that the tow undergoes as tension varies. This departure from conventional friction dynamics in this context provides crucial insights into carbon fiber tow spreading as dependency in contact pressure, tow width, and slip rate could be deconvoluted. Building on these findings, we propose a novel method for determining the friction of a roving through a spreader bar system that accounts for the effects of pulling speed, pre-tension, (a)symmetricity of the local wrap angles etc., and thus leading to a higher fidelity of the resulting microstructure of unidirectional thin-ply carbon fiber [7].