Types of Reinforcement


As a consequence of the heterogeneity of composite materials, initial defects are difficult to be eliminated completely. To guarantee the structural safety of these materials it is necessary to investigate the effects of their defects under service conditions. When a composite material is loaded, different types of damage will occur matrix cracking, delamination fibre/matrix debonding and fibre failure. Some of these damage types will initiate even at a very low load level, without causing overall failure of the composite part. However, during further loading the initial damage will grow and create other types of damage. The fatigue damage accumulation in fibre reinforced composite materials can be evaluated by different Non Destructive Testing (NDT) techniques. The most commonly used NDT techniques to date have been the ultrasonic C-scan and the x-ray radiography for detecting primarily internal delamination and matrix cracking respectively. Nevertheless, an interruption of the fatigue loading and removal of the specimen from the test fixture is usually required, which may affect the fatigue results.  [c.45]

Operated broadband amplifier 1, has uniform (not worse than 1 dB) frequency feature within the range of 1 to 50 MHz and the range of reinforcement from 0 to 90 dB. The input cascade has an impedance switch that enables to matching of sensors of different types and to avoid signals and distortions caused by the cable.  [c.731]

Tlie focus of discussions presented so far in this publication has been on the finite element modelling of polymers as liquids. This approach is justified considering that the majority of polymer-fonning operations are associated with temperatures that are above the melting points of these materials. However, solid state processing of polymers is not uncommon, furthermore, after the processing stage most polymeric materials are used as solid products. In particular, fibre- or particulate-reinforced polymers are major new material resources increasingly used by modern industry. Therefore analysis of the mechanical behaviour of solid polymers, which provides quantitative data required for their design and manufacture, is a significant aspect of the modelling of these materials. In this section, a Galerkin finite element scheme based on the continuous penalty method for elasticity analyses of different types of polymer composites is described. To develop this scheme the mathematical similarity between the Stokes flow equations for incompressible fluids and the equations of linear elasticity is utilized.  [c.183]

Cera.micA.bla.tors, Several types of subliming or melting ceramic ablators have been used or considered for use in dielectric appHcations particularly with quartz or boron nitride [10043-11 -5] fiber reinforcements to form a nonconductive char. Fused siHca is available in both nonporous (optically transparent) and porous (sHp cast) forms. Ford Aerospace manufactures a 3D siHca-fiber-reinforced composite densified with coUoidal siHca (37). The material, designated AS-3DX, demonstrates improved mechanical toughness compared to monolithic ceramics. Other dielectric ceramic composites have been used with performance improvements over monolithic ceramics (see COMPOSITE MATERIALS, CERAMIC MATRIX).  [c.5]

Pulpstone Wheels. Grinding wheels play an important role in the production of paper pulp (qv). Massive pulpstone wheels are made from vitrified abrasive segments, bolted and cemented together around a reinforced concrete central body. They may be up to 1.80 m in diameter and have a breadth of 1.70 m. In operation, debarked wood logs are fed into a machine and forced against the rotating pulpstone, which shreds the wood into fibers under a torrent of water. The ground fibers are then screened and passed through subsequent operations to produce various types of paper.  [c.15]

Electronics and electrical insulation are other manufacturing areas in which advanced fibers are extensively used. Manufacturing of computer components such as printed circuit boards and printed wiring boards require use of reinforced fibers that have good dielectric properties, thermal and dimensional stabiHty, chemical resistance, and low moisture regain. Eor electrical insulation appHcations, fiber requirements are high dielectric strength, low power loss, and good thermal and chemical resistance. Although inorganic fibers are extensively used for both electronic and electrical appHcations, aramid fibers are also now used for both types of appHcations. A variety of natural and synthetic fibers are also used for various electrical appHcations (37).  [c.72]

Rubber Compounding. Hydrocarbon resins are used in the production of various types of mbber-based products, including tires, shoe soles and heels, hoses, industrial belting, mats, electrical wire insulation, and roU coverings. Coumarone—indene and aromatic resins reinforce mineral-loaded SBR stock and increase tensile strength, elongation, and resistance to flex cracking. The aHphatic- and terpene-based resins are used as tackifiers for NR and NR/SBR combinations in the formulation of tires and molded goods. Aromatic modified aHphatic or functionally modified aromatic resins can act as both tackifying and reinforcing resins. Normally a range of 5—15 parts of resin per 100 parts of elastomer is used in mbber compounding.  [c.358]

Many cellular plastic products are available with different types of protective faces, including composite metal and plastic foils, fiber-reinforced plastic skins, and other coatings. These reduce but do not eliminate the rate of aging. For optimum performance, such membranes must be totally adhered to the foam, and other imperfections such as wrinkles, cuts, holes, and unprotected edges should be avoided because they all contribute to accelerated aging.  [c.334]

Improving Properties Through Compounding. The potential value of most polymers can be realized only after proper compounding. Materials used to enhance polymer properties or reduce polymer cost include antioxidants (qv), cross-linking agents, accelerators, fillers (qv), plasticizers (qv), adhesion promoters, pigments (qv), etc. Antioxidants are essential to retard degradation in unsaturated polymers. Cross-linking agents are used to build modulus, resistance to permanent deformation, and greater solvent resistance in many types of polymers. Accelerators are frequently used to reduce the time and temperature required to affect the cross-linking. Fillers, such as carbon black (qv) and clays (qv), do not reinforce latex polymers as they do their dry polymer counterparts. Rather, they are used in most latex appHcations to adjust processing rheology and to lower raw materials costs of the product, or to impart specific effects, eg, aluminum trihydrate to increase resistance to flame degradation, or carbon black to increase resistance to uv degradation. Plasticizers and oils are used to soften and increase flexibiUty at lower temperatures, improve resistance to crystallization, or depress the brittle point of the product. Hydrocarbon process oils, glycols, vegetable oils, ester plasticizers, and low melting point resins are some of the common materials used. Many types of resins are added to enhance the tackiness of polymers. Generally, within a class of tackifying resins, the lower the melting point, the greater the tack developed in the compounded polymer. The optimum amount of any resin for maximum tack depends on the type of polymer to which it is added. Resins added as solvent-cut emulsions rather than as solventless emulsion or dispersions develop more tack in the polymer, because the residual solvent in the polymer contributes to the tack of the polymer resin blend. Pigments and dyes are used to impart color. Some pigments with some polymers also impart other effects such as improved water resistance or reduced flammabiUty.  [c.28]

Glass Manufacture. Both high calcium limestone and dolomite are high volume batch iagredients for many types of glass (qv), television picture tubes, fiat glass (for wiadows, automotive glass, and mirrors), light bulbs, food and beverage containers, glass tableware, and glass fiber (for reinforcement and iasulation). The glass fiber iadustry generaUy uses quicklime, whereas dried, double-screened limestone or dolomite is generaUy used ia other glass products. Because magnesium oxide enhances durabUity and weatherabUity, dolomite (or dolomite along with limestone) is specified for neatly aU glass types except one-use nonretumable beverage containers. Glass companies requite raw materials that are consistent ia siting and chemistry after shipment. They have estabUshed very strict limits for both the iron content of the ore itself (typicaUy <0.1%, but as low as 0.06%), and for contaminating metallic material like stainless steel or aluminum.  [c.179]

Mechanical and Thermal Design. The main objectives of channel mechanical and thermal design are to maintain stmctural and sealing integrity, to provide adequate cooling of gas-side surface elements, and to use efficiendy the magnet bore volume, ie, to maximize the ratio of channel flow cross-section area to the magnet bore cross-section area. This last requirement affects not only the channel mechanical design but also the packaging of channel electrical wires, cooling hoses, and manifolds. In broad terms, MHD channels built to date have fallen into one of three types of constmction categories plastic box constmction window frame constmction or reinforced window frame constmction.  [c.431]

Laminated MMCs. There are three types of laminated MMCs (/) metallic matrix-containing fibers oriented at different angles in different layers, similar to that of polymeric laminates (2) two or more different metallic sheets bonded to each other and (3) laminated metal/discontinuously reinforced MMC.  [c.203]

Sealers. Mica is used in all types of sealers for porous surfaces, such as waHboard masonry, and concrete blocks, to reduce penetration and improve holdout (see Sealants). It permits a thicker film to be appHed and at the same time reduces sagging. Cracking is reduced by the reinforcing action of the flakes, and gaps and holes in rough masonry are bridged by the mica flakes.  [c.291]

There are three basic types of screen surfaces perforated or punched plate, woven cloth, and profile bars. Woven cloth surfaces are the most common. Perforated plates are made up of hardened steels, stainless steels. Monel, mbber, or plastic. Woven cloth can be made from high carbon steels, tempered steels, manganese steels, galvanized steel. Monel, copper, bronze, or reinforced synthetic cloths of polyurethane mbber. Screens can handle material ranging from the fineness of talc through boulders as large as 2 x 2 m weighing as much as 10—12 tons. Screen openings range from 0.1 mm to as large as 500 mm.  [c.399]

Common open-mold processes are hand or mechanized methods such as lay-up and spray-up, that use a single cavity mold and produce one finished surface (85). These techniques are used to produce fiber-reinforced stmctures containing the reinforcement in the form of cloth, chopped strands, mat, continuous roving, woven roving, etc. Thermosetting resins of choice are liquid unsaturated polyester or epoxy resins. In lay-up, catalyzed resin is used to impregnate the reinforcement that is preplaced on the mold. A spray-up system consists of a resin spray gun, a fiber chopper and a pumping system the catalyst is combined with the resin just before deposition with the fibers onto the mold surface. Open-mold processes use fltde or no pressure during the curing cycle. Cross-linking usually takes place at room or slightly elevated temperature through a proper combination of curing agents. A variety of products such as boat hulls, automotive components, tanks, etc are made by open-mold processing (86). Types of emissions and U.S. environmental regulations for thermoset components and cure reaction by-products are included in Reference 87.  [c.144]

Thermal Properties. The high melting point of polyamides such as nylon-6,6 is a function of the strong hydrogen bonding between the chains and the crystal stmcture. This also allows the materials to retain significant stiffness above the glass-transition temperature (Ip and almost up to the melting point. The effect is further increased when reinforcements such as glass fiber are added, giving a high deflection temperature under load even at high loading. The effect also results in the sharp melting points of nylon as the majority of the hydrogen bonding rapidly breaks down at that temperature, giving a low viscosity, water-like melt. The melting point is mainly related to the degree of hydrogen bonding between the chains, which depends on the density of amide groups. The melting point therefore drops as the length of aUphatic groups between the amide links increases, eg, nylon-6,6 melting at 264°C, compared to nylon-6,12 at 212°C. The influence of stmcture on the melting point is further compHcated by factors that affect the ease of crystallization. For even—even nylons such as nylon-6,6 and nylon-6,12, the monomers have a center of symmetry and the amide groups easily align to form hydrogen bonds in whichever direction the chains are facing when placed on top of one another. For even nylons, such as nylon-6, that have no center of symmetry, the amide groups are in the correct positions only if the chains are aligned in one particular direction (antiparallel). For this reason, nylon-6 has a melting point more than 40°C lower than nylon-6,6, despite having the same density of amide groups. It also has a slower crystallization rate and therefore wider processing window. Other types of nylon, such as even—odd and odd nylons, also differ from the above types for similar reasons of crystallization and crystal packing (see PoLYAMiDES, GENERAL). In addition, crystallization is impeded and melting point reduced by copolymerization and substituents on the chains, although in certain cases isomorphism of comonomers avoids this effect, eg, terephthaUc acid increases the melting point of nylon-6,6.  [c.267]

Rubber. In mbbet, talc is used as a reinforcing agent and processing aid in mechanical mbbet goods and as a patting agent in a variety of thermoset mbbet processes. Talc, micronized by fluid energy milling, is capable of increasing the modulus of typical cured synthetic elastomers by 300% at loadings of 100 pht and is used in a wide range of belt, cable, and hose appHcations. It is also a rheology improver and process aid for extmded mbbet goods at use levels of 10 to 50 pht. Coarser (—200-mesh (ca 74 -lm)) talc is an excellent patting agent for all types of mol ding appHcations such as tires, elastomeric thread, and printing trays.  [c.302]

Processing Oils. Individual fibers used for reinforcement purposes are quite small, on the order 10—20 micrometers in diameter, and are sensitive to damage resulting from abrasion by contact with machine parts during manufacture. Oils are appHed during this process and serve to lubricate the filament bundle and act as wetting agents to assist the spreading and adhesion of coatings appHed at later stages of processing (34). As such, processing oils must be amenable to a wide range of uses. Thek formulation is highly proprietary based in general on the use of modified fatty acid esters. Other types of finish can also act as adhesive activators for later processing.  [c.84]

The combination of asbestos fibers with various types of natural or synthetic resins has led to the development of a variety of products and appHcations. Among those, the incorporation of asbestos fibers (mainly chrysotile) into mbber matrices yields materials that ate widely used for fabrication of packings and gaskets. Complex formulations, comprising short asbestos fibers (usually chrysotile), resins, and other fillers and modifiers, have been developed as friction materials for brake linings and pads. Asbestos fibers have also found broad apphcation as reinforcing agents in fillers (qv), coatings, sealings, and adhesive formulations.  [c.354]

Carbon Composites. Cermet friction materials tend to be heavy, thus making the brake system less energy-efficient. Compared with cermets, carbon (or graphite) is a thermally stable material of low density and reasonably high specific heat. A combination of these properties makes carbon attractive as a brake material and several companies are manufacturing carbon fiber—reinforced carbon-matrix composites, which ate used primarily for aircraft brakes and race cats (16). Carbon composites usually consist of three types of carbon carbon in the fibrous form (see Carbon fibers), carbon resulting from the controlled pyrolysis of the resin (usually phenoHc-based), and carbon from chemical vapor deposition (CVD) filling the pores (16).  [c.273]

Polypropylene can be fabricated by almost any process used for plastics (see Plastics processing). The extmsion of pipe and injection mol ding of fittings present no unusual problem. However, there is no way to bond the fittings to the pipe except by remelting the polymer, which is impractical on most constmction sites. The resin can be reinforced by glass fibers, mineral fillers, or other types of fillers and can be pigmented readily.  [c.327]

While concrete pipe will have trouble being cost competitive, its poor corrosion-resistant properties can be overcome with the use of PVC liners, putting it in a position to compete against PVC pipe on its superior cmsh resistance. The more recent news in PVC and HDPE pipe manufacturing is geared toward materials saving, as the price of resin has risen dramatically. PVC foam-core pipe reduces material consumption up to 40% and tooling is currently appHcable to DWV pipe from 1—20-cm (0.5 to 8-in.) diameters. Small-diameter, alurninum-reinforced, cross-linked HDPE pipe consists of an aluminum tube sandwiched between inner and outer layers of cross-linked HDPE. Current availabiLity is for diameters of 1—20 cm. This pipe is impermeable to gas, immune to corrosion, and is easier to blend and install than either all-aluminum or aH-HDPE pipe. It is rated to 1 MPA (150 psi) at temperatures over 90°C, making it appHcable for closed indoor heating systems. Two new types of cormgated pipe with smooth inner bores, each produced by a proprietary system, have now met all specifications for sewer pipe and are said to provide material savings of up to 50% over conventional PVC pipe (40,75,76).  [c.336]

Galvanic corrosion (1—3,8) occurs as a result of the electrical contact of different metals in an aggressive environment. The driving force is the electrode potential difference between the two metals. One metal acts principally as a cathode and the other metal as the anode. Galvanic corrosion can result from the presence of a second phase in a metal. An example is manganese sulfide [18820-29-6] MnS, inclusions in steels. Galvanic corrosion is also an important consideration for the environmental stabiHty of metal matrix composites (qv) such as graphite reinforced alurninum. Galvanic corrosion can accelerate many of the other types of corrosion.  [c.274]

Some of the common types of plastics that ate used ate thermoplastics, such as poly(phenylene sulfide) (PPS) (see Polymers containing sulfur), nylons, Hquid crystal polymer (LCP), the polyesters (qv) such as polyesters that ate 30% glass-fiber reinforced, and poly(ethylene terephthalate) (PET), and polyetherimide (PEI) and thermosets such as diaHyl phthalate and phenoHc resins (qv). Because of the wide variety of manufacturing processes and usage requirements, these materials ate available in several variations which have a range of physical properties.  [c.32]

Care should be taken in selecting the mounting for applications where the motor weight would apparently fall on its flange or the foot, as in mountings /)5, B6, B8, V3. V5 and V6. In such mountings, the foot or the flange is subject to a shearing force due to a cantilever effect and is vulnerable to breakage. For small sizes, where the weight of the motor may not matter so much, these types of mountings can be employed, otherwise reinforcement may be necessary either to the foot or to the tlange, if possible. For larger motors it is advisable to select an alternative mounting.  [c.20]

Modified Bitumen Membranes. These membranes were developed in Europe during the late 1950s and have been used in the United States since the late 1970s. There are two basic types of modified asphalts and two types of reinforcement used in the membranes. The two polymeric modifiers used are atactic polypropylene (APP) and styrene—butadiene—styrene (SBS). APP is a thermoplastic polymer, whereas SBS is an elastomer (see Elastomers, thermoplastic elastomers). These modified asphalts have very different physical properties that affect the reinforcements used.  [c.321]

The toughness induced in ceramic matrices reinforced with the various types of reinforcements, that is, particles, platelets, whiskers, or fibers, derives from two phenomena crack deflection and crack-tip shielding. These phenomena usually operate in synergism in composite systems to give the resultant toughness and noncatastrophic mode of failure.  [c.49]

There are, of course, many more aspects of composite hardware design that differ from metallic bonded structure but do not necessarily involve adhesive bonding. For instance there are many types of reinforcement tape and fabric to choose from, the orientation of the plies must be chosen, the ply stackups must be balanced to avoid part warping after cure, a minimum number of plies must be used to prevent non-visible impact damage that significantly affects the load carrying capability of the part, etc.  [c.1182]

Melting ablators such as nylon and quartz perform essentially as subliming ablators do, except that they melt. In general, melting ablators have heats of reaction similar to subliming ablators but have much higher thermal conductivities. When compared to other types of ablative materials, there are very few advantages to using melting ablators. However, they are often combined with charring ablative materials in a reinforcing fiber form to improve ablation performance by transpirational cooling as the endothermic melt is forced to the surface (38). Some melting ablators have also found appHcation as dielectric ablators, when no electrically conductive residue is formed. SiHcon carbide and siHcon nitride [12033-89-5] have also been considered as effective ablators for specific thermal protection appHcations (39).  [c.5]

Polydimethyl Siloxane. The development of organic—inorganic networks began in the early to mid-1980s using polydimethylsiloxane (PDMS) oligomers. This polymer was chosen because of the close stmctural similarity between the siloxane chains and the expected sol—gel-derived siUca. Hence, it is also an ideal organic—inorganic glass. Similar synthetic approaches were employed independentiy by two groups. One approach focused on improving the mechanical properties of PDMS by using the sol—gel processing of metal alkoxides to generate inorganic "fillers" (siUca, titania, alumina, and zirconia) within the PDMS network during or after the development of a cross-linked PDMS network (1 9). In all cases, the hybrids generated by either the simultaneous curing and filling or the precipitation of the inorganic component within an existing swollen network in situ precipitation) showed significantly better reinforcement than the network containing fumed siUca, an alternate reinforcing agent. Electron microscopy of the hybrids synthesized using the in precipitated siUca shows that the inorganic phase does not agglomerate into large particles within the original PDMS network (2,4). Rather, most particles fall in the range of 20 to 30 nm and are very finely dispersed. Small-angle x-ray scattering (saxs) experiments of these reinforced networks demonstrated that under strongly basic conditions and large excesses of water, uniformly dense nonfractal particles resulted (6). Conversely, under acidic or neutral conditions, more polymeric stmctures resulted. The thermal stabiUty of in situ filled PDMS networks was also studied using thermogravimetric analysis (tga), and it was demonstrated that this type of reinforcement enhances the thermoxidative stabiUty of ordinary PDMS and fumed siUca-reinforced PDMS (9). This reference also provides an excellent review of the different types of sol—gel-derived reinforcement studied (9).  [c.328]

The industrial grade of propylene glycol is an important intermediate in the production of alkyd resins for paints and varnishes. It is the preferred glycol for manufacturing high performance, unsaturated polyester resins for many uses, eg, reinforced plastic laminates for marine constmction, gel coats, sheet mol ding compounds (SMC), and synthetic marble castings. It is also used as a solvent and plasticizer in printing inks, as a preservative in floral arrangements, and as a stabilizer in hydrauHc fluids. Heat-transfer fluids used in commercial and industrial building heating and cooling systems, chemical plants, stationary engines, and solar heat recovery can be formulated with the industrial grade of propylene glycol. More recently, propylene glycol-based coolants for automobiles and heavy-duty diesel engine tmcks have been introduced which compete with traditional ethylene glycol-based products (28,29). The newly pubflshed ASTM standard D5216 specifies aqueous propylene glycol-based engine coolants for automobile and light-duty tmck service. AH heat-transfer apphcations requite corrosion inhibitor additives and are designed for specific operating temperature ranges and types of materials of constmction. Operation at low temperature without freezing and at high temperature without excessive pressure are the principal features of these systems.  [c.368]

Civil Engineering and Construction. These textile appHcations can be classified as civil engineering appHcations (also commonly referred to as geotextiles (qv)) and architectural appHcations. High performance fibers are not currently used to any great extent in these appHcations due to their high unit cost. However, mechanical and environmental requirements for such appHcations demand that even conventional fibers withstand challenging stmctural demands and sustained long-term performance outdoors. Polypropylene fibers have captured a sizable portion of the geotextile market because of their exceUent dimensional stabiHty and chemical inertness. Polyester and glass fibers are two other types of fibers used in geotextile appHcations. Reinforcement of highways and roadbeds is by far the principal use of geotextiles. Their primary function is to serve as a soil stabilizer by spreading the impact load of vehicles over a larger area thus prolonging the useful life of roadways. As in agricultural appHcations, geotextiles are also used to prevent or minimize soil erosion and faciHtate drainage. These materials have been utilized in important projects such as reinforcement of dikes in HoUand and to constmct dams in the United States. Mechanisms for geotextile failure have been criticaUy evaluated and discussed (39). The types of failure must be evaluated relative to the function of the geotextile. PaUure modes include piping of soils through or clogging of the geotextile, reduced tensile resisting force, deformation of the fabric, reduced resistance to puncture, and reduced in-plane flow to Hquids.  [c.72]

Advanced composites and fiber-reinforced materials are used in sailcloth, speedboat, and other types of boat components, and leisure and commercial fishing gear. A ram id and polyethylene fibers are currentiy used in conveyer belts to collect valuable offshore minerals such as cobalt, uranium, and manganese. Constmction of oil-adsorbing fences made of high performance fabrics is being evaluated in Japan as well as the constmction of other pollution control textile materials for maritime use. For most marine uses, the textile materials must be resistant to biodeterioration and to a variety of aqueous pollutants and environmental conditions.  [c.73]

Oxide and Fiber-Reinforced Superalloys. Apart from the aligned eutectics, two other approaches promise to improve the maximum service temperature of turbine blade materials oxide dispersion strengthened superaHoys (ODSS), and oxidation-resistant alloys reinforced with refractory metal fibers. The properties of some FRS alloys are compared with those of superaHoys in Figure 13 (66). When the density-compensated stress—mpture resistance of these advanced aHoys is compared with that of MarM-200 + Hf, a commercial directionaHy solidified superaHoy to which hafnium is added, the strength of the superaHoy can be approximately doubled by the advanced aHoys at temperatures in excess of 1000°C. However, a detailed cost estimate for manufacturing turbine blades of each of the four types of aHoys indicates that a substantial cost penalty is assumed with aligned eutectics. Dispersion-strengthened aHoys and fiber-reinforced superaHoys (FRS), however, may be more competitive with conventional aHoys, especiaHy because some fiber-reinforced superaHoys may not require coatings.  [c.129]

Deformation processing of metal—metal composites involves mechanical processing (swaging, extmsion, drawing, or rolling) of a ductile two-phase material. The two phases co-deform, causing the minor phase to elongate and become fibrous in nature within the matrix. These materials are sometimes referred to as in situ composites. The properties of a deformation processed composite depend largely on the characteristics of the starting material which is usuahy a bihet of two-phase ahoy that has been prepared by casting or powder metahurgy methods (see Metallurgy, powder). RoU bonding is a common technique used to produce a laminated composite consisting of different metals in sheet form (5). Such composites are cahed sheet laminated metal-matrix composites. RoU bonding and hot pressing have also been used to make laminates of A1 sheets and discontinuously reinforced MMCs (6,7). Figure 5 shows the roU bonding process of making a laminated MMC. Other examples of deformation processed metal-matrix composites are the niobium-based conventional filamentary superconductors and the silver-based high superconductors. There are two main types of the conventional niobium-based superconductors Nb—Ti/Cu and Nb Sn/Cu. Niobium—titanium ( 50 50) form a ductile system. Rods of Nb—Ti are inserted in holes driUed in a block of copper, evacuated, sealed, and subjected to a series of drawing operations interspersed with appropriate annealing treatments to give the final composite superconducting wire. This process is fairly straightforward. In the case of Nb Sn/Cu, a process cahed the bronze route is used to make this composite. Nb Sn, an A-15-type bhtde intermetaUic, cannot be processed like Nb—Ti. Instead, the process starts with a bronze (Cu—13% Sn) matrix, pure niobium rods are inserted in holes ddhed in bronze, evacuated, sealed, and subjected to wire drawing operations as in the case of Nb—Ti/Cu. The critical step is the heat treatment (- 700° C) that drives out the tin from the bronze matrix to combine with niobium to form stoichiometric, superconducting Nb Sn, leaving behind copper matrix. A process that is increasingly gaining importance is cahed the oxide-powder-in-tube (OPIT) method (8). In this process, the oxide powder of appropriate composition (stoichiometry, phase content, impurities, etc) is packed inside a metal tube (generahy silver), sealed, and degassed. Commonly, swaging and drawing are used for making wires and rolling is used for tapes. Heat treatments, intermediate and/or subsequent to deformation, are given to form the correct phase, promote grain interconnectivity and crystahographic alignment of the oxide, and obtain proper oxygenation (8).  [c.196]

Spray-Forming of Particulate MMGs. Another process for making particle-reinforced MMCs involves the use of spray techniques that have been used for some time to produce monolithic alloys (11). One particular example of this, a co-spray process, uses a spray gun to atomize a molten aluminum ahoy matrix, into which heated (for drying) shicon carbide particles ate injected (Fig. 8). An optimum particle size is requited for an efficient transfer, eg, whiskers are too fine to be transferred. The preform produced in this way is generahy quite porous. The co-sprayed metal-matrix composite is subjected to scalping, consoHdation, and secondary finishing processes, thus making it a wrought material. The process is totahy computer controUed and is quite fast, but it should be noted that it is essentiahy a Hquid metahurgy process. The formation of deleterious reaction products is avoided because the time of flight is extremely short. Shicon carbide particles of an aspect ratio (length /diameter) between 3—4 and volume fractions up to 20% have been incorporated into aluminum ahoys. An advantage of the process is the flexibhity it affords in making different types of composites, eg, in situ laminates can be made using two sprayers or by selective reinforcement. This process is quite expensive, however, mainly because of the capital equipment.  [c.197]

Stiffness Loss in Fa.tigue, The complexities in composites lead to the presence of many modes of damage, such as matrix cracking, fiber fracture, delamination, debonding, void growth, multidirectional cracking, etc. In the case of the isotropic material, a single crack propagates in a direction perpendicular to the cycHc (mode I) loading axis (Fig. 16). In the fiber-reinforced composite, on the other hand, a variety of subcritical damage mechanisms (Fig. 17) lead to a highly diffuse damage 2one, and these multiple fracture modes appear rather early in the fatigue life of composites. The various types of subcritical damage result in a reduction of the load carrying capacity of the laminate composite, which in turn manifests itself as a reduction of laminate stiffness and strength (46—50). The stiffness changes in the laminated composites to the accumulated damage under fatigue have been experimentally related. The change in stiffness values is a good indicator of the damage in composites, thus stiffness loss in continuous fiber-reinforced MMCs can be a usehil parameter for detecting fatigue damage initiation and growth. This progressive loss of stiffness during fatigue of composites is a characteristic that is very different from the behavior of metals in fatigue. Similar loss of stiffness has been observed on subjecting a fiber-reinforced composite to thermal fatigue (51).  [c.203]

Fine particle-size dry ground mica is also used as an extender and filler in certain texture and traffic paints. Mica particles are stronger than iron and not brittle like other inerts. It is an antifriction, antifouling, antisettling, anticorrosive, antitarnish, and antisiege agent. It is a superior reinforcing pigment that acts as a sealer over porous surfaces and reduces penetration and flushing (see Sealants) moreover, it improves the moisture resistance of protective coatings and adhesion to all types of surfaces.  [c.292]

Rubber-Modified Polystyrene. Rubber is incorporated into PS primarily to impart toughness. The resulting materials, commonly called high impact polystyrene (HIPS), are available in many different varieties. In mbber-modifted PS, the mbber is dispersed in the PS matrix in the form of discrete particles. The mechanism of mbber particle formation and mbber reinforcement, as well as several reviews of HIPS and other heterogeneous polymers, have been pubHshed (21,22,66—70). The photomicrographs in Figure 5 show the different morphologies possible in HIPS materials prepared using various types of mbbers (71,72). If the particles are much larger than 5—10 micrometers, poor surface appearance of moldings, extmsions, and vacuum-formed parts are usually noted. Although most commercial HIPSs contain ca 3—10 wt % polybutadiene or styrene—butadiene copolymer mbber, the presence of PS occlusions within the mbber particles gives rise to a 10—40% volume fraction of the reinforcing mbber phase (22,73). Accordingly, a significant portion of the PS matrix is filled with mbber particles. Techniques have been pubhshed for evaluating the morphology of HIPS (72,74,75).  [c.507]

Several types of organic fibers are used the ceUulose-based include cotton (hntets), solkafloc, paper (qv), sisal, and other natural fibers synthetics include acryflcs and polyaromatics. Unique ate the acryflc and polyaromatic pulps made by microcutting the surfaces of softened fibers. The high surface and charge effects impart processabiUty as well as low temperature reinforcement properties at the expense of higher costs. Carbon—graphite fibers are produced by carbonization—graphitization of organic or pitch fibers by techniques that provide parallel alignment of the carbon chain to the fiber length for maximum tensile strength.  [c.274]

Built-Up Roofing. BUR has been used since the late 1800s with a variety of reinforcements. Fiber glass mat and organic felt are the reinforcements used today in the United States fiber-glass mat is used in most of the material produced. BUR roofing systems use several types of felts or reinforcements between layers of asphalt, to build up the roof. Asphalt is used to provide waterproofing and to glue the layers together the reinforcement is used to span imperfection in the substrate, and strengthen and stabilize the asphalt against flow and movement. The most common type of felt used to constmct roofs is called a ply felt. Additionally, a coated base sheet, or ply sheet coated with filled coating on each side, is used when the roof must be nailed to the substrate rather than adhered. Some roofs may use a cap sheet, or a heavily coated sheet with granules on the top side, for anesthetic reasons.  [c.321]

Swimming Pools and Spas. Swimming pools ia the United States are both ia-ground and above-ground types for residential, commercial, and iastitutional markets. There is a need for a vapor barrier ia the coastmctioa of pools for which caleadered (flexible) PVC is the primary material used. By their aature, above-grouad pools are coacrete (63%), fiberglass (3%), or vinyl-lined (34%). A replacement pool market parallels the types of pools mentioned above. Above-grouad pools coasume about 54% of the PVC used as pool liners, and ia-ground types consume the rest. The replacement market is beginning to dominate the consumption of PVC for both types of pools based on the already high and escalating cost of new pools. Vinyl-lined pools are maintained easily, typically cost less than prepackaged alternatives, and are available in a variety of designs. Their disadvantages include limited flexibihty in design/shape and the perception that they are cheap. Eiber glass, typically reinforced polyester, is characterized by longer life and ease of cleaning but suffers from limited sizes/shapes, limited colors, avaHabiUty only near manufacturing sites, and sensitivity to improperly maintained poolwater chemistry. Concrete pools offer design flexibihty, more permanent/stronger perception, and status orientation but are more costly than alternatives, require more chemicals, and are more difficult to clean.  [c.333]

Glass Fibers. Glass fibers represent the most frequentiy used reinforcement in modem polymer composites. This popularity results from their relatively low cost and high tensile strength. In bulk form, glass is brittie, having a relatively low strength. However, when extmded and drawn into fine fibers, the strength of glass increases enormously, by as much as two orders of magnitude. Glass-fiber-reinforced composites are currentiy used in a wide variety of appHcations, including boat constmction and the automotive and aerospace industries. Many types of glass fiber are available, each having specific properties and characteristics. The most commonly used fibers. E-glass, contain approximately 14% AI2O2, 18% CaO, 5% MgO, 8% B2O2, and 1% Na20 + K2O as well as siUca (see Glass).  [c.5]

In a typical screw assembly, the flights are fabricated, then welded to a pipe that has bushings press-fitted or welded into each end to provide reinforcing for the conveyor couplings. There are two types of flights heUcoid and sectional.  [c.157]

Dental cements are composites, ie, they have a continuous or matrix phase linked to a discontinuous or reinforcing phase by an interphase. Based on their chemistry, dental cements can be divided into acid—base cements, acryUc or resin cements, and resin-modified acid-base cements, ie, hybrid cement composites. Acid—base cements are either aqueous-based cements or nonaqueous-based cements, although small amounts of water or protoic agents are essential to the acid-base setting mechanism of the latter. AcryUc cements are resin-based composites modified for cement appHcations. The monomer(s) used in these cements can be simply methyl methacrylate [80-62-6] or various types of multifunctional monomers, eg, BIS-GMA [1565-94-2] triethylene glycol dimethacrylate, [2351-42-0] etc. The setting mechanism is by free-radical addition polymeri2ation, either chemical, photochemical, or a combination of the two. The hybrid cement-composites include a vinyl resin system as well as the usual acid—base components of the cement. They have a dual, ie, ionic and free radical, setting mechanism.  [c.472]

ASME Code Sec. X Fiberglass—Reinforced-Plastic Pressure Vessels This section is limited to four types of vessels bag-molded and centrifugally cast, each limited to 1,000 kPa (150 Ibfiiu") filament-wound with cut filaments hmited to 10,000 kPa (1500 Ibf/iu ) and filament-wound with uncut filaments limited to 21,000 kPa (3000 Ibf/ in"). Operating temperatures are hmited to the range from -i-66°C (150°F) to -54°C (-65°F). Low modulus of elasticity and other property differences between metal and plastic required that many of the procedures in Sec. Xbe different from those in the sections governing metal vessels. The requirement that at least one vessel of a particiilar design and fabrication shall be tested to destruction has prevented this section from being widely used. The results from the combined fatigue and burst test must give the design pressure a safety factor of 6 to the burst pressure.  [c.1026]

Equipment Costs vaiy widely for a given diameter because of the many types of construction. As a general rule, the total installed cost will be about 3 to 4 times the cost of the raking mechanism (including drivehead and lift), plus walkways and bridge or centerpier cage, railings, and overflow launders. Figure 18-93 shows the approximate installed costs of thickeners up to 107 m (350 ft) in diameter. These costs are to be used only as a guide. They include the erection of mechanism and tank plus normal uncomphcated site preparation, excavation, reinforcing bar placement, backfill, and surveying. The price does not include any electrical work, pumps, piping, instrumentation, walkways, or lifting mechanisms. Special design modifications, which are not in the price, could include elevated tanks (for underflow handhng) special feedwell designs to control dilution, entrance velocity, and turbulence electrical and drive enclosures required because of climatic conditions and mechanism designs required because of scale buildup tendencies.  [c.1691]


See pages that mention the term Types of Reinforcement : [c.5]    [c.152]    [c.251]    [c.544]   
See chapters in:

Plastics engineering Изд.3  -> Types of Reinforcement