The most common measuring method to characterise the dynamic yarn path in the ring spinning process is to measure the yarn tension, where the yarn path is almost straight. However, it is much more complex to measure the yarn tension at the other positions, for example, between the yarn guide and traveller (balloon zone) and between the traveller and winding point of the cop (winding zone), as the yarn rotates continuously around the spindle axis. In this paper, two new methods of yarn tension measurement in the balloon zone are proposed. In the first method, the balloon shape was first recorded with a high speed camera. The balloon tension was then calculated by comparing the yarn strain (occurring in the balloon zone) measured by a digital image analysis program with the stress-strain curve of the yarn produced. In the second method, the radial forces of the rotating balloon were measured by using modified measurement techniques for measurement of yarn tension. Moreover a customised sensor was developed to measure the winding tension between the traveller and cop. The values measured were validated with a theoretical model and a good correlation between the measured and theoretical values could be revealed.
The new concept of a superconducting magnetic bearing (SMB) system can be implemented as a twisting element instead of the existing one in a ring spinning machine, thus overcoming one of its main frictional limitations. In the SMB, a permanent magnet (PM) ring rotates freely above the superconducting ring due to the levitation forces. The revolution of the PM ring imparts twists similarly to the traveler in the existing twisting system. In this paper, the forces acting on the dynamic yarn path resulting from this new technology are investigated and described with a mathematical model. The equation of yarn movement between the delivery rollers and the PM ring is integrated with the Runge-Kutta method using MATLAB. Thus, the developed model can estimate the yarn tension and balloon form according to different spindle speeds considering the dynamic behavior of the permanent magnet of the SMB system. To validate the model, the important relevant process parameters, such as the yarn tension, are measured at different regions of the yarn path, and the balloon forms are recorded during spinning with the SMB system using a high speed camera.Keywords mathematical modeling, yarn tension, balloon form, ring spinning, superconducting magnetic bearingIn the existing ring spinning process, the frictional heat generated in the ring/traveler system causes damage to both the twisting element and the yarn structure. 1 The traveler is not allowed to rotate at more than 50 m/s, especially in the case of man-made fibers, due to their melting, caused by the high friction-induced heating, which limits productivity. 2,3 The friction-free superconducting magnet bearing (SMB) eliminates this restriction and thus allows increase of the spindle speed much higher than with existing spinning machines. In our previous work, different concepts of SMB system have been presented, and a suitable one has been successfully integrated in a ring spinning tester. 4 The SMB system comprises of two rings, a magnetic element of Neodymium Iron Boron (NdFeB) with a yarn guide attached to it, and a high temperature superconductor (SC) from YBCO (YBa 2 Cu 3 O 7-x ) chemical compounds. The superconductor (SC) ring is cooled down below its critical temperature at a fixed distance from the PM ring. The PM ring levitates above the SC ring according to the principle of levitation. During the spinning process, the yarn (wound onto the bobbin) rotates the PM ring, instead of the traveler. The patented concept of the SMB system ensures a smooth running of the spinning process for significantly higher productivity with similar yarn properties to the conventional process. 5
Based on in situ strain sensors consisting of piezo-resistive carbon filament yarns (CFYs), which have been successfully integrated into textile reinforcement structures during their textiletechnological manufacturing process, a continuous load of fibre-reinforced plastic (FRP) components has been realised. These sensors are also suitable for structural health monitoring (SHM) applications. The two-dimensional sensor layout is made feasible by the usage of a modular warp yarn path manipulation unit. Using a functional model of a small wind turbine blade in thermoset composite design, the sensor function for basic SHM applications (e.g. static load monitoring) are demonstrated. Any mechanical loads along the pressure or suction side of the wind turbine blade can be measured and calculated via a correlative change in resistance of the CFYs within the textile reinforcement plies. Performing quasi-static load tests on both tensile specimen and full-scale wind turbine blade, elementary results have been obtained concerning electro-mechanical behaviour and spatial resolution of global and even local static stresses according to the CFY sensor integration length. This paper demonstrates the great potential of textile-based and textile-technological integrated sensors in reinforcement structures for future SHM applications of FRPs.
Joining textile layers to a preform using patches is of utter importance in regards to producing structural elements made of fibre-reinforced materials with complex geometry, and repairing fibre-reinforced composites in an efficient and safe manner. Material-efficient and load-specific design and integration of the patch are essential in relation to the performance of the joint as well as the strengthening of the composite structure after a damaging event. Hence, in this study, the stress–strain behaviour of carbon-fibre-reinforced epoxy-composites, which are joined by a patch designed as double-lap joint, will be investigated. It will be shown that the woven fabric morphology (surface structure) and the woven fabric construction (weave pattern) of the join partners exert a noticeable influence on the stability of the patched composite samples. The use of leno non-crimp fabrics as patch structures, which provide an increased joint surface in comparison to the likewise examined twill fabrics, enables a growth in joint strength, provided that the dimensions of the patch remain the same.
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