Fibrous reinforcement

The tensile and flexural properties as well as resistance to cracking in chemical environments can be substantially enhanced by the addition of fibrous reinforcements such as chopped glass fiber. Mechanical properties at room temperature for glass fiber-reinforced polysulfone and polyethersulfone are shown in Table 5. 

The primary constituent of practically ah. asbestos—organic friction materials was asbestos fiber, with smah quantities of other fibrous reinforcement material. Asbestos was chosen because of its thermal stabhity, its relatively high friction, and its reinforcing properties. Because asbestos alone did not offer ah of the desked properties, other materials cahed property modifiers were added to provide desked levels of friction, wear, fade, recovery, noise, and rotor compatibihty. A reski bkider held the other materials together. This bkider is not completely neutral and makes contributions to the friction and wear characteristics of the composite. The more commonly used kigredients can be found ki various patents (6—9). 

Organic clutch materials contain continuous-strand reinforcements in addition to fibrous reinforcements. These include cotton (primarily for processing), other organic yams, carbon—graphite yam, and asbestos yam, and brass wire or copper wire for high burst strength. 

This is also known as Bulk Moulding Compound (BMC). It is blended through a mix of unsaturated polyester resin, crosslinking monomer, catalyst, mineral fillers and short-length fibrous reinforcement materials such as chopped glass fibre, usually in lengths of 6-25 mm. They are all mixed in different proportions to obtain the required electromechanical properties. The mix is processed and cured for a specific time, under a prescribed pressure and temperature, to obtain the DMC. 

E. O. Dickerson and B. OiMartino, Off-Axis Strength and Testing of Filamentary Materials for Aircraft Application, in Advanced Fibrous Reinforced Composites, Vol. 10, Society of Aerospace Materials and Process Engineers, 1966, p. H-23. 

Apart from the conditions of load transmission from fiber to matrix, the anisotropy of mechanical characteristics is also due to the considerable anisotropy of the fibers themselves in the longitudinal and transverse directions, especially in the case of fibrous reinforcements of polymeric nature [154]. 

Particulate fillers provide better creep resistance than unfilled plastics but are less effective than fibrous reinforcements. 

In designing fibrous-reinforced plastics it is necessary to take into account the combined actions of the fiber and the plastic. At times the combination can be considered homogeneous, but in most cases homogeneity cannot be assumed. 

This low pressure process, also known as elastic reservoir molding, consists of making basically a sandwich of plastic-impregnated open-celled flexible polyurethane foam between the face layers of fibrous reinforcements. When this plastic composite is placed in a mold and squeezed, the foam is compressed, forcing the plastic outward and into the reinforcement. The elastic foam exerts sufficient pressure to force the plastic-impregnated reinforcement into contact with the heated mold surface. Other plastics are used. 

Oldfield, C. W. B. Ellis, B. (1991). Fibrous reinforcement of glass-ionomer cements. Clinical Materials, 7, 313-24. 

A plastics material of particular application in electrical components. It consists of a thermosetting polyester resin, mineral fillers, fibrous reinforcement and a hquid crosslinking medium such as diallyl phthalate. Down-Stroking Press... 

The price of the fibrous reinforcements (Figure 2.14) depends on the nature of the fibres and the form of the reinforcement continuous or chopped fibres, mats, rovings, fabrics or unidirectional. 

Many naturally occurring materials such as wood are reinforced composites consisting of a resinous continuous phase and a discontinuous fibrous reinforcing phase. 

The modulus of thermosets, such as phenolic plastics, is much greater than that of thermoplastics because of the high cross-link density present in thermosets. Since these network polymers are brittle, they are usually toughened by the addition of fibrous reinforcements. 

The durability of polymers may also be improved by the addition of reinforcing fillers and fibrous reinforcements (F) to the polymer matrix (M). The modulus of a composite is a function of the distribution (amount and orientation) of the fibers,/, the modulus of each component, G, and the partial volume of the fiber, C, as shown by the following equation ... 

The orientation effect is magnified when the compound contains fibrous reinforcement which tends to align itself with the direction of milling. The amount of orientation depends upon the viscosity of the stock as well as the type of rubber and type of fiber. 

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