Filament lay

Filament lay Length of twist produced by stranding filaments, such as fibers, wires, or rovings angle that such filaments make with the axes of the strand during a stranding operation. The length of twist of a filament is usually measured as the distance parallel to the axis of the strand between successive turns of filaments. 

The lay down system is required to intermingle the fibre bundles into a web of good coverage and uniform fabric weight. It is preferred to generate a single filament lay... 

As already described, the lay down units between the two different systems are different as well. With open systems, the filament lay down is realized either by just blowing the filaments on to the belt, spreading them up by means of electrostatic forces, distributing the filaments with static or dynamic deflection plates or moving flaps or combinations hereof. With the help of such lay down systems, it is possible to generate an MD/CD ration of one. 

Stress in a Cord. Twisting two or more filaments together to form a cord reduces the overall modulus and strength of the constmction. The degree of the reduction depends on the individual filaments (55). If the lay length is significantly higher than the filament diameter, the stress is... 

Ease of cure, easy removal of parts from mold surfaces, and wide availabiHty have made polyesters the first choice for many fiber-reinforced composite molders. Sheet mol ding compound, filament winding, hand lay-up, spray up, and pultmsion are all weU adapted to the use of polyesters. Choosing the best polyester resin and processing technique is often a challenge. The polyester must be a type that is weU adapted to the processing method and must have the final mechanical properties requked by the part appHcation. Table 1 Hsts the deskable properties for a number of fiber-reinforced composite fabrication methods. 

Part Design Blow Molding Casting Compression Extrusion Filament Winding Injection Matched Die Molding Rotational Thermo- forming Transfer Compression Wet lay-up (Contact Molding)... 

Compression molding Filament winding Hand lay-up Mat molding Pressure bag molding Continuous pultrusion Injection molding Spray-up... 

On-line consolidation techniques are commonly used in manufacturing processes, such as filament winding and tape laying. Despite differences in the machines used to implement these two manufacturing processes, similar procedures are required to ensure complete bonding between the composite layers. The basic components of on-line consolidation process are illustrated in Figure 7.2. 

The scale of the cells within the multifilament strand is controlled by two factors (1) the number of primary filaments bundled into the second feedrod, and (2) the size of the extrusion die used to form the second filament. The number of filaments bundled into the second feedrod is determined by both the size of the primary filaments and the size of the second feedrod. The decreasing ratio of extrusion die sizes results in a dramatic increase in the number of cells within a strand. In addition to making finer cell sizes possible, it is also much easier to lay coarse multifilament strands into a die than it is to lay small fibers. The strands lay straight and flat, whereas fibers tend to curl up and become intertwined. However, despite the fine cell size, the coarseness of the strands limits their use to architectures in which the scale of a cluster of cells is no less than 0.75 mm. 

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