Mansour H. Mohamed

Comparison of Physical Properties of Fabrics Woven from Open-End and Ring Spun Yarns

It is well established that open-end yarns are different from ring yarns; in particular OE yarns are weaker and more bulky in spite of the higher twist levels used. The introduction of these yarns into woven fabric affects the structure and the characteristics of the fabrics. The fabric structure traps non-load bearing fibers and thus gives increases in fabric strength and decreases in fabric extensibility. Crimp levels are altered which affect the initial modulus and the breaking extension of the fabric. This and the different yarn characteristics lead to considerable difference in tear strength. In the cases, of both ring and OE fabrics, the looser the structure, the worse the pilling performance and the better the tear performance. Compromises have to be made according to end-use. The changes in structure alter the topography of the fabric which affects the wear behavior. The changes in structure also affect the crease resistance and flexural rigidity characteristics of the fabrics. Thus the differences in the yarn structure play a distinct part in determining the final nature of the fabric.

The Performance of Open-End, Twistless, and Ring Yarns in Weft Knitted Fabrics:

Open-end, twistless, and ring yarns made from cotton and spun to different twists were knitted into single-jersey fabrics to assess their performance. Further tests at a given twist level for a range of polyester/cotton yarns were also included. A variety of yarn and fabric relaxations were used, and it was evident that unrelieved torque is a prime cause of loop distortion, spirality, and fabric shrinkage. It became apparent that autoclaving the yarns was the best way of reducing twist liveliness and the associated difficulties in manufacturing the fabric; it also improves the properties of the fabric. Properly relaxed, open-end yarn makes a fabric with good appeal, reasonable shrinkage, and acceptable strength and abrasion resistance. Twistless yarns gave good fabric hand, high luster, zero spirality, and little shrinkage, but there was some loss in strength for the fabric tested.

Fabrication and characterization of three-dimensional cellular-matrix composites reinforced with woven carbon fabric

Abstract A low-density three-dimensional cellular-matrix composite reinforced with woven carbon fabric (3DCMC), was fabricated by means of a pressure-quenching molding technique with nitrogen gas as the blowing agent. Epoxy resins in the interstices of yarns in the 3DCMC samples were vacated during the foaming process and needle shaped voids were also generated between fibers in yarns. The average density of the 3DCMC samples was about 10 3 kg/m 3 , and their density reduction was 28–37% compared with a regular matrix composite with the same preform. The 3DCMC has 32–42% higher specific tensile strength, 14–37% greater specific tensile modulus, a lower specific flexure strength but 35% higher specific tangent modulus in 3-point bending, a 30–40% higher specific impact energy absorption at an impact velocity around 120 m/s and a similar specific energy absorption at about 220 m/s. Meanwhile, the 3-point bending and impact test results of 3DCMC showed that they have different fracture mechanisms from that of 3DRMC.

Analysis of Yarn Motion in Single-nozzle Air—jet Filling Insertion. Part I: Theoretical Models for Yarn Motion

Dynamic analysis of air-jet filling insertion has been carried out both experimentally and theoretically for unsteady-state running conditions. In Part I of this series, analytical models for both loop- and drum-storage systems are developed to investigate the air-jet filling-insertion process. The flight of the yarn in an air jet is a complex dynamic problem, which is affected by many factors, such as air velocity and yarn characteristics, as well as the yarn-storage and yarn-feeding systems. Theoretical analysis shows that the yarn velocity can be increased by increasing the air/yarn frictional force and by decreasing the yarn tension. Numerical solutions for the equations of yarn motion are obtained

Mechanics of a Single Nozzle Air-Jet Filling Insertion System Part I: Nozzle Design and Performance

The effect of nozzle design on the air velocity for an air-jet filling insertion system has been investigated. The relationship between the supply air pressure and the air velocity at the nozzle axis is explained using a simplified model for the nozzle. The presence of the yarn tube has a substantial influence on nozzle performance. The interaction between the jet and the air guide system (in the form of a tube) is discussed in terms of the ratio of the guide diameter to the nozzle diameter.

Weft Insertion on Air- jet Looms: Velocity Measurement and Influence of Yarn Structure Part I: Experimental System and Computer Interface

An account la given of an experimental system developed for automated data acquisition In air–jet weft insertion. The air–jet–loom simulator and the computer interface for measuring the insertion time, air and yarn velocities, and air pressure ln the system are described.

Analysis of Yarn Tension in Air-Jet Filling Insertion

Yarn tension during air-jet filling insertion is analyzed experimentally and theo retically for drum and loop storage systems. In the case of drum storage, yarn tension is higher and more even. The model for drum storage shows that the yarn tension depends on the frictional force between the drum surface and the yarn, the mass linear density of the yam, and the unwinding speed. A set-up is developed for air friction coefficient measurements, and friction coefficients for two different yarns are deter mined.

Mechanics of a Single Nozzle Air-Jet Filling Insertion System Part III: Yarn Insertion Through Tubes

Yarn insertion through regular and slotted tubes (simulating the air guide system on air-jet looms) has been investigated. A theoretical analysis describing the yarn movement during insertion and the equation of motion is presented. The effects of the conditions behind the nozzle on yarn insertion are shown in terms of the loop length and the speed of the feeding system. Experimental results of yam insertion using different conditions for the various parameters are discussed. Good agreement between experimental and theoretical results was found.

Weft Insertion on Air-jet Looms: Velocity Measurement and Influence of Yarn Structure Part II: Effects of System Parameters and Yarn Structure

An investigation of the effects of different weft–insertion–system parameters on yarn velocity is reported. Increasing the air–supply pressure, initial loop length, and running speed decreases the total insertion time and hence increases the average yarn velocity. To examine the effects of yarn characteristics on yarn velocity, several yarns were tested under the same laboratory conditions. For every yarn, relations between total insertion time, yarn velocity, and air velocity and distance were obtained. It was found that open–end–spun (OE) yarns had a higher yarn velocity than ring–spun (R) yarns owing to the bulkier structure. However, R yarns had a higher initial acceleration than OE yarns. Murata air–jet–spun yarns had a higher velocity than R yarns. Increasing the yarn linear density and twist increased the insertion time. Texturing of continuous–filament yarns increased the yarn velocity by comparison with straight continuous–filament yarns.

Mechanics of a Single Nozzle Air-Jet Filling Insertion System Part II : Velocity Distribution and Design of the Air Guide System

The air velocity distribution along the air guide system of an air-jet loom is affected by the initial air velocity at the nozzle and the design of the guide system. In this paper, the air velocity distribution along regular and slotted tubes (simulating a new air guide system) is presented in terms of the tube configuration and its interaction with the jet at the tube entrance.