# Fabrication of Low-Twist and High-Strength Metallic Fibre Hybrid Spun Yarns
## 3 Results and Discussion
### Effect of ARSTs on Tensile Properties  
The results of the tensile properties of noncompact plain (NCP), compact plain (CP), noncompact SIRO (NCS) and compact SIRO (CS) yarns are presented in Figure 5. It was surprising to observe that the NCP yarn showed unexpectedly higher tenacity than that of CP yarn produced even at the same machine and operating parameters. During the  
Figure 4: Effect of yarn plying and twisting on tensile properties of MFHYS. processing of NCP yarn on a K-44 machine with pneumatic compaction inactive, the edge fibres are not fully integrated into the yarn body, and some fibres may escape the twisting effect due to the wider width of drafted roving and consequently outflowing the spinning triangle. These escaped fibres are either wasted as a fly or attached disorderly in the yarn, as exposed in Figure 6, under PS8 NCP. However, in CP yarn, the edge fibres are relatively more integrated and orderly arranged into the yarn body due to the unique attributes of the compact spinning system [51]. The compact yarns exhibit better packing density, compact structure and lower hairiness with improved fibre utilization [52]. Therefore, the tenacity of CP yarn should always be higher than that of NCP yarn. However, it was astonishing to note that despite all the constant operating parameters of spinning geometry, spindle speed, T.N. and TC, the tenacity of CP yarn was lower than that of NCP yarn. Although the elongation at break of CP yarn is somewhat better than that of NCP yarn. The tenacity might be lower due to a decrease in yarn tension (the force produced by the rotation of the traveller around the ring and dragging of yarn by winding cope through the traveller) during spinning,  
Figure 5: Effect of ARSTs parameters on tensile properties and hairiness of yarns. Figure 6: Yarn formation zone of plain and SIRO, compact and noncompact yarns. which should be high enough to increase the yarn tenacity and compact winding over the cope. The yarn tension is a crucial factor in improving the yarn tenacity since it affects the transmission of twist from the traveller to the nip line of front rollers with consequent firm gripping of fibres in the yarn body resulting from narrowing the width of the spinning triangle [31,53]. However, an optimum yarn tension is necessary to establish a smooth running of the process, less ends down rate, stable package density and better package density of the cop. Other than yarn tension, the hairiness-S3 value of CP yarn is also very close to that of NCP yarn, which should be reduced significantly for the true compact structure of CP yarn. The yarn tension, which is directly related to the frictional drag of the traveller, represented by Equation (4), generally depends on fibre characteristics, spindle speed, traveller weight, ring diameter, yarn count and delivery rate of the spinning machine [54,55]. To increase the traveller's weight, a traveller with a larger T.N is used. In this case, when T.N was increased from 8.0 to 14.0 with all other parameters kept constant, the tenacity of CP yarn was increased from 24.30 cN tex\({}^{-1}\) to 25.78 cN tex\({}^{-1}\). An increase in T.N caused an increase in yarn tension, which resulted in a significant decrease in hairiness-S3 value from 840 to 392, thus confirming the compact structure of CP yarn with firm gripping and better utilization of fibres in the yarn body. \[F=\mu MR_{R}\omega^{2} \tag{4}\]  
where:  
\(F=\) Frictional drag of the traveller (N);  
\(\mu=\) Coefficient of friction between the ring and traveller;  
\(M=\) Mass of the traveller (Kg);  
\(R_{R}=\) Ring radius (m);  
\(\omega=\) Angular velocity of the traveller ( \(=2\pi Nt\));  
\(Nt=\) Traveller speed (rpm). In the case of SIRO yarns, the tenacity and elongation at the break of compact SIRO (CS) yarn are better than that of noncompact SIRO (NCS) yarn.