Effect of inter-tow angle and temperature on the static coefficient of friction of preimpregnated tows in tow-tow and tow-metal contact

The objective of this study is to quantify the frictional properties of tow materials utilized in filament winding processes for the manufacturing of carbon fiber reinforced plastic (CFRP). The study aimed to investigate the influence of inter-tow angle (ITA) and temperature on the static coefficient of friction (sCoF) of commercially available towpregs. A series of experiments was conducted to measure the frictional behavior of the towpregs under varying ITA’s (0° to 90°) and temperatures (22 °C to 60 °C). The results demonstrate a clear correlation between ITA and friction. Lower angles (0°-10°) exhibit higher friction due to mechanical entanglement and embedding. At higher angles (20°-90°), the static coefficient of friction decreases, reaching a minimum at 90°. Furthermore, temperature has been identified as a crucial factor in reducing friction. Compared to 22 °C, at 30 °C, a 35% decrease in the static coefficient of friction was observed, while at 50 °C, a 54% reduction was noted. Beyond this point, the friction levels appear to stabilize, suggesting that the resin viscosity and friction properties reach a plateau. A supportive rheological analysis of the resin system revealed a notable decline in viscosity with elevated temperatures, which further substantiates the observed reduction in friction. These findings highlight the combined influence of tow alignment and thermal conditions on the sCoF, with significant implications for the design and processing of composite materials in filament winding. The results indicate that meticulous consideration of ITA and temperature is essential for optimizing composite material performance, particularly in filament winding applications. The results of the work can be summarized as follows: • The inter-tow angle exerts a considerable influence on the sCoF between a towpreg and a towpreg substrate on the surface. • Lower inter-tow angles (0–10°) resulting in higher friction compared to higher angles due to entanglement and embedding between towpregs. • Inter tow angles higher than 10° result in a decline in the sCoF. The sCoF was measured at its lowest at an inter tow angle of 90°, which was 25% below the sCoF of the 0° inter tow angle. • Temperature also plays a critical role, as increased temperatures lead to a significant reduction in the sCoF for both tow-metal (54% for 60 °C) and tow-tow contact (down to 66% for 60 °C and 90° inter-tow angle). • The reduction rate of the static friction coefficient under the influence of temperature at 0° and 90° inter-tow angle exhibits a notable discrepancy. The entanglement and embedding of towpregs contribute to a diminished reduction of the sCoF for parallel towpregs. As temperature rises, the effect is further amplified by the decline in resin viscosity.