Reinforced plastics fibrous reinforcements

Nishino T, Hirao K and Kotera M (2006) X-ray diffraction studies on stress transfer of keuaf reinforced poly(L-lactic acid) compoate, Composites Part A 37 2269-2273. You L H, You X Y and Zheng Z Y (2006) Thermomechanical analysis of elastic-plastic fibrous composites comprising an inhomogeneous interphase, Comput Mater Sci 36 440-450. 

Two approaches have been taken to produce metal-matrix composites (qv) incorporation of fibers into a matrix by mechanical means and in situ preparation of a two-phase fibrous or lamellar material by controlled solidification or heat treatment. The principles of strengthening for alloys prepared by the former technique are well estabUshed (24), primarily because yielding and even fracture of these materials occurs while the reinforcing phase is elastically deformed. Under these conditions both strength and modulus increase linearly with volume fraction of reinforcement. However, the deformation of in situ, ie, eutectic, eutectoid, peritectic, or peritectoid, composites usually involves some plastic deformation of the reinforcing phase, and this presents many complexities in analysis and prediction of properties. 

Table 13 is a representative Hst of nickel and cobalt-base eutectics for which mechanical properties data are available. In most eutectics the matrix phase is ductile and the reinforcement is britde or semibritde, but this is not invariably so. The strongest of the aHoys Hsted in Table 13 exhibit ultimate tensile strengths of 1300—1550 MPa. Appreciable ductiHty can be attained in many fibrous eutectics even when the fibers themselves are quite britde. However, some lamellar eutectics, notably y/y —5, reveal Htde plastic deformation prior to fracture. 

Laminates ate a special form of composite material or reinforced plastic because the continuous reinforcing ply of fibrous material imparts significant strength in the x—j plane. The strength along the axis results from interlaminar bonding of resins. Very few fibers ate oriented in the direction, so it tends to be the weak link in this type of composite. 

The mechanical properties of plastics materials may often be considerably enhanced by embedding fibrous materials in the polymer matrix. Whilst such techniques have been applied to thermoplastics the greatest developents have taken place with the thermosetting plastics. The most common reinforcing materials are glass and cotton fibres but many other materials ranging from paper to carbon fibre are used. The fibres normally have moduli of elasticity substantially greater than shown by the resin so that under tensile stress much of the load is borne by the fibre. The modulus of the composite is intermediate to that of the fibre and that of the resin. 

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

Based on this analysis it is evident that materials which are biaxially oriented will have good puncture resistance. Highly polar polymers would be resistant to puncture failure because of their tendency to increase in strength when stretched. The addition of randomly dispersed fibrous filler will also add resistance to puncture loads. From some examples such as oriented polyethylene glycol terephthalate (Mylar), vulcanized fiber, and oriented nylon, it is evident that these materials meet one or more of the conditions reviewed. Products and plastics that meet with puncture loading conditions in applications can be reinforced against this type of stress by use of a surface layer of plastic with good puncture resistance. Resistance of the surface layer to puncture will protect the product from puncture loads. An example of this type of application is the addition of an oriented PS layer to foam cups to improve their performance. 

Reinforced plastics (RPs) hold a special place in the design and manufacturing industry because they are unique materials (Figs. 6-11 and 6-12). During the 1940s, RPs (or low-pressure laminates, as they were then commonly known) was easy to identify. The basic definition then, as now, is simply that of a plastic reinforced with either a fibrous or nonfibrous material. TSs such as polyester (Table 6-19) and E-glass fiber dominated and still dominates the field. Also used are epoxies. 

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. 

Asbestos It is not the name of a distinct mineral species but is a commercial term applied to fibrous varieties of several silicate minerals such as amosite and crocido-lite. These extremely fine fibers are useful as fillers and/or reinforcements in plastics. Property performances include withstanding wear and high temperatures, chemical resistance, and strengths with high modulus of elasticity. When not properly handled or used, like other fibrous materials, they can be hazardous. 

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 Tg value is reduced by the addition of moderate amounts of plasticizers (additive which reduces intermolecular forces) and is sometimes even increased by the addition of small amounts of plasticizers (antiplasticization) and optimum amounts of fillers (usually a relatively inert material used as the discontinuous phase of a composite) and reinforcements (materials such as fibrous additives which give increased strength to a polymer). 

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. 

Subclass B2 is formed by the so-called structural composites, in which an outspoken mechanical reinforcement is given to the polymer. Subgroup B21 consists of blends of polymers with compatible anti-plasticizers subgroups B22 are the most important the fibre-reinforced polymer systems. The two components, the polymer matrix and the reinforcing fibbers or filaments (glass, ceramic, steel, textile, etc.) perform different functions the fibrous material carries the load, while the matrix distributes the load the fibbers act as crack stoppers, the matrix as impact-energy absorber and reinforcement connector. Interfacial bonding is the crucial problem. 

Basically a plastic composite is the assembly of two or more materials made to behave as a single product. Examples include vinyl-coated fabric used in air mattresses or laminated metal bonded together with a plastic adhesive used in helicopter blades. The RP type of composite combines a plastic with a reinforcing agent that can be fibrous, powdered, spherical, crystalline, or whisker, made of organic, inorganic, metallic, or ceramic material. To be structurally effective, there must be a strong adhesive bond between the resin and reinforcement. 

Filament winding (FW) is a fabrication technique for forming reinforced plastic parts of high strength/modulus and lightweight. It is made possible by exploiting the remarkable strength properties of their continuous fibers or filaments encased in a matrix of a resinous material. For this process, the reinforcement consists of filamentous non-metallic or metallic materials processed either in fibrous or tape forms.488 489... 

The performance expected from a sealant and the polymer used in its production determine the type of fillers used. From the point of view of performance, sealants can be divided into these having plastic behavior and these with elastomeric behavior. Sealants which have plastic behavior are low-cost and low-performance products which are being gradually eliminated from the market. These sealants use inexpensive fillers to lower cost and regulate non-sag properties. Typical fillers used in these products are calcium carbonate and some fibrous materials which are used as replacement for asbestos which was very popular in the past. This combination of fibrous and spherical particles provided a useful tool to the sealant formula-tor to regulate non-sag properties which are very important in sealants. Fibers have also been used to reinforce these products because the properties of polymers were poor. 

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