1st week unanswered words

Previous Definition: Matrix Materials: (Group: Materials)

The matrix phase can be any of three basic material types; polymers, metals, or ceramics. The secondary phase may also be one of the three basic materials, or it may be an element such as carbon or boron. Possible combinations in a two-component composite material can be organized as a 3 * 4 chart. We see that certain combinations are not feasible, such as a polymer in a ceramic matrix. We also see that the possibilities include two-phase structures consisting of the same material type, such as fibers of Kevlar (polymer) matrix. In other composites the imbedded material is an element such as carbon or boron. 

(Mikell P.Groover, Fundamentals of Modern Manufacturing , page 188-189)

New Definition: Matrix Materials: (Group: Materials) (better)

The polymer matrix resins include both thermosetting and thermoplastic types, with emphasis on the former because they account for more than 80% of all matrices in reinforced plastics and essentially all matrices used in advanced composites. The most widely used thermosetting resins are the polyesters, which are most often combined with E-glass. This combination accounts for the bulk of the fiber-reinforced plastics (FRP) market. Polyesters offer a combination of low cost, versatility in many processes, and reasonably good property performance unmatched by any other resin type. The most common orthophthalic types and the premium isophthalic types, bisphenol A fumarate, chloendic, and vinyl ester, are discussed in this Section.

For more demanding structural uses, epoxy resins are the preferred candidates. Although the amount of epoxies used in reinforced plastics is small in comparison to the volume of polyester used, epoxy use dominates the more demanding aircraft/aerospace structural applications. Epoxy resins are of particular interest to structural engineers because they provide a unique balance of chemical and mechanical properties combined with extreme processing versatility. Epoxy resin performance is highly dependent on the formulation, which includes the base resin, curatives, and the modifiers. A practical introduction to these basic formulary components and epoxy- resin selection is provided in this Section.

Several high-temperature polymeric matrices are also covered, including cyanate ester, polyimide, and bismaleimide resins. These tend to be more expensive resin systems, and are employed in applications where the high-temperature performance justifies the additional cost. Cyanate esters, or polycyanurates, bridge the gap in thermal performance between engineering epoxy resins and high-temperature polyimides. Polyimide resins are used when optimum thermal stability at high temperature is required. Although polyimides may be thermosetting or thermoplastic, most composite applications use the thermosetting types, which are fully covered in this Section. The addition-type bismaleimide (BMI) resins are also covered in this Section.

The use of high-performance thermoplastics as matrices in continuous fiber reinforced composites is currently an area characterized by very low use but very high interest. This Section addresses continuous fiber reinforced thermoplastics. The focus is on materials suitable for fabrication of structural laminates such as might be used for aerospace.

The Section also includes articles that address metallic, ceramic, and carbon matrices, including the distinct advantages and limitations of these materials.

Intermediate Material Forms: Also covered in this Section are some of the intermediate material forms available for composite fabrication. These are often used as components that are joined with other components and assembled into a structure, and/or as ways of arranging and controlling the fiber architecture. Examples include sandwich core materials, fabrics and preforms, fiber mats, and braids. While the coverage is not comprehensive, the articles offer the engineer a shopping list that complements the Sections in this Volume that focus on design, manufacturing, and material properties. A key advantage of working with composite materials is the opportunity to integrate material properties, design, and manufacturing technique so that the end product—a completed structure—is optimized from both a performance and an economics standpoint.

(ASM Handbook Volume 21 Composites, ASM INTERNATIONAL The Materials Information Company, page 66,67)

Previous Definition: RESİN (Group: Material) (better)

A resin is a high-molecular-weight organic material with no sharp melting point. Resins usually exhibit a tendency to flow when subjected to stress, and they fracture in a ductile mode. Most resins are polymers. In reinforced plastics, the resin is the material used to bind together the reinforcement material (i.e., the matrix).
(Harper C.A., Petrie E.M., Plastics Materials and Processes: A Concise Encyclopedia, p.482)

New Definition: RESİN (Group: Material)

Composites with organic (resin) matrices are emphasized throughout this Volume, because these OMCs are by far the most commonly used structural composites. Nonetheless, MMCs are now an established technology with strong impact and growing applications, and so MMCs are discussed explicitly throughout this Volume. Only very limited discussion of CMCs is provided in this Volume. (p:46)

Organic matrices for commercial applications include polyester and vinyl ester resins; epoxy resins are used for some “high-end” applications. Polyester and vinyl ester resins are the most widely used of all matrix materials. They are used mainly in commercial, industrial, and transportation applications, including chemically resistant piping and reactors, truck cabs and bodies, appliances, bathtubs and showers, and automobile hoods, decks, and doors. The very large number of resin formulations, curing agents, fillers, and other components provides a tremendous range of possible properties.

The development of highly effective silane coupling agents for glass fibers allowed the fabrication of glassfiber- reinforced polyester and vinyl ester composites that have excellent mechanical properties and acceptable environmental durability. These enhanced characteristics have been the major factors in the widespread use of these composites today. The problems of attaining adequate adhesion to carbon and aramid fibers have discouraged the development of applications for polyester or vinyl ester composites that use these fibers.  Although there are applications of high-performance fiberglass composites in military and aerospace structures, the relatively poor properties of advanced composites of polyester and vinyl ester resins when used with other fibers, combined with the comparatively large cure shrinkage of these resins, have generally restricted such composites to lowerperformance applications.

Other Resins. When property requirements justify the additional costs, epoxies and other resins, as discussed subsequently, are used in commercial applications, including high performance sporting goods (such as tennis rackets and fishing rods), piping for chemical processing plants, and printed circuit boards. Organic matrices for aerospace applications include epoxy, bismaleimide, and polyimide resins. Various other thermoset and thermoplastic resins are in development or use for specific applications.

Epoxy resins are presently used far more than all other matrices in advanced composite materials for structural aerospace applications. Although epoxies are sensitive to moisture in both their cured and uncured states, they are generally superior to polyesters in resisting moisture and other environmental influences and offer lower cure shrinkage and better mechanical properties. Even though the elongation-to-failure of most cured epoxies is relatively low, for many applications epoxies provide an almost unbeatable combination of handling characteristics, processing flexibility, composite mechanical properties, and acceptable cost. Modified “toughened” epoxy resin formulations (typically via the addition of thermoplastic or rubber additives) have improved elongation capabilities. In addition, a substantial database exists for epoxy resins, because both the U.S. Air Force and the U.S. Navy have been flying aircraft with epoxy-matrix structural components since 1972, and the in-service experience with these components has been very satisfactory. Moisture absorption decreases the glass transition temperature (Tg) of an epoxy resin. Because a significant loss of epoxy properties occurs at the Tg, the Tg in most cases describes the upper-use temperature limit of the composite. To avoid subjecting the resins to temperatures equal to or higher than this so-called wet Tg (the wet Tg is the Tg measured after the polymer matrix has been exposed to a specified humid environment and allowed to absorb moisture until it reaches equilibrium), epoxy resins are presently limited to a maximum service temperature of about 120 °C (250 °F) for highly loaded, long- term applications and even lower temperatures (80 to 105 °C, or 180 to 220 °F) for toughened epoxy resins. Although this limit is conservative for some applications, its imposition has generally avoided serious thermal-performance difficulties. Considerable effortcontinues to be expended to develop epoxy resins that will perform satisfactorily at higher temperatures when wet. However, progress in increasing the 120 °C (250 °F) limit has been slow. Bismaleimide resins (BMI) possess many of the same desirable features as do epoxies, such as fair handleability, relative ease of processing, and excellent composite properties. They are superior to epoxies in maximum hot/wet use temperature, extending the safe in-service temperature to 177 to 230 °C (350 to 450 °F). They are available from a number of suppliers. Unfortunately, BMIs also tend to display the same deficiencies (or worse) as do epoxies: they have an even lower elongation-to-failure and are quite brittle. Damage tolerance is generally comparable to commercial aerospace epoxy resins. Progress has been made to formulate BMIs with improved toughness properties. Polyimide resins are available with a maximum hot/wet in-service temperature of 232 °C (450 °F) and above (up to 370 °C, or 700 °F, for single use short periods). Unlike the previously mentioned resins, these cure by a condensation reaction that releases volatiles during cure. This poses a problem, because the released volatiles produce voids in the resulting composite. Substantial effort has been made to reduce this problem, and there are currently several polyimide resins in which the final cure occurs by an addition reaction that does not release volatiles. These resins will produce good-quality, low- void-content composite parts. Unfortunately, like BMIs, polyimides are quite brittle.

Other Thermosetting Resins. The attempt to produce improved thermosetting resins is ongoing, with majör efforts focusing on hot/wet performance and/or impact resistance of epoxies, BMIs, and polyimides. Other resins are constantly in development, and some are in commercial use for specialized applications. Phenolic resins, for example, have been used for years in applications requiring very high heat resistance and excellent char and ablative performance. These resins also have good dielectric properties, combined with dimensional and thermal stability. Unfortunately, they also cure by a condensation reaction, giving off water as a byproduct and producing a voidy laminate. However, they also produce low smoke and less toxic by-products upon combustion and are therefore often used in such applications as aircraft interior panels where combustion requirements justify the lower properties. Cyanate esters are also used as matrix materials. Their low-moisture absorption characteristics and superior electrical properties allow them to see applications in satellite structures, radomes, antennas, and electronic components.

Thermoplastic Resins. The dual goal of improving both hot/wet properties and impact resistance of composite matrices has led to the development, and limited use, of high temperature thermoplastic resin matrices. These materials are very different from the commodity thermoplastics (such as polyethylene, polyvinyl chloride, and polystyrene) that are commonly used as plastic bags, plastic piping, and plastic tableware. The commodity thermoplastics exhibit very little resistance to elevated temperatures; the high-performance thermoplastics exhibit resistance that can be superior to that of epoxy.

Thermoplastic-matrix materials are tougher and offer the potential of improved hot/wet resistance and longterm room-temperature storage. Because of their high strains-to-failure, they also are the only matrices currently available that allow, at least theoretically, the new intermediate-modulus, high-strength (and strain) carbon fibers to use their full strain potential in the composite. Thermoplastics are generally considered to be semicrystalline (meaning the atoms in the polymer chains arrange themselves in regular arrays to some degree) or amorphous (meaning there is no local order to the molecular chains). These materials include such resins as polyether etherketone, polyphenylene sulfide, polyetherimide (all of which are intended to maintain thermoplastic character in the final composite), and others, such as polyamideimide, which is originally molded as a thermoplastic but is then postcured in the final composite to produce partial thermosetting characteristics (and thus improved subsequent temperature resistance). Thermoplastic matrices do not absorb any significant amount of water, but organic solvent resistance is an area of concern for the noncrystalline thermoplastics.

(ASM Handbook Volume 21 Composites, ASM INTERNATIONAL The Materials Information Company, page 46-49-50-51)

Previous Definition: Reinforced Plastics (Group: Material) (better)

An important class of composites are reinforced plastics that consist of fibers are dispersed in a discontinious manner within a continious matrix of polymer.Reinforced plastics with more than one type of fiber are said to be hybrid.The commonly used fiber materials include glass,graphite,boron nylon,silicon nitride,silicon carbide etc.

(Rapid prototyping : laser based and other technologies,Patri K. Venivinod,Weiyin Ma,p:52)

New Definition: Reinforced Plastics (Group: Material)

All thermosetting moulding materials can be regarded as ‘reinforced’ since the liquid resin is unmouldable unless mixed with fillers, which have the effect of reinforcing it. As the industry has developed, however, it has adopted mainly fibrous or filament forms of reinforcing materials, which provide considerable mechanica strength. Thermoplastics, while also often using an element of filler, can b moulded without a specific reinforcement, but the additiob of such a material can considerably extend mechanical properties.

The concept of reinforcing a resin is as old as the first really synthetic resin, dating back to 1908, when the chemist Baekeland made the discovery tht phenolic resin could processed if filled (or reinforced) with wood flour. The main use of these compounds was in electrical insulating components. Reinforced plastics are we know them today, however, have grown up with the aircraft industry (which neededd strong lightweight materials and had no preconceived ideas). Resin- stiffened fabric was used early in the 1920s: Micarto was used by Dowty for propellers before 1920 and Harzell in USA used mixture of fabric and phenolic reinforcement, Hartzine, for propellers made prior to the 1940s. Aero Research UK produced a composite of flax linen with urea formaldehyde before World War II.

(John Murphy, The reinforced plastics handbook 2nd ed. , p: ix, introduction)

Previous Definition: LAYOUT DESİGN (Group: Design) (better)

The overall layout design, developed from the function structure, determines the

division of a product into assemblies and components and:

• identifies the source of the components; that is, whether they are in-house,

bought-out, standard or repeat parts

• determines the production procedure; for instance whether the parallel production

of individual components or assemblies is possible

• establishes the dimensions and the approximate batch sizes of similar components,

and also the means of joining and assembly

• defines suitable fits

• influences quality control procedures.

(Engineering Design A Systematic Approach; G. Pahl, W. Beitz; Page: 356)

New Definition: LAYOUT DESİGN (Group: Design)

Layout design (also called embodiment design) presents a general arrangement of the conceptual design with appropriate dimensions. Ashby maps can be used to facilitate consideration of all possible generic classes of materials at this very early stage in the design process. Ashby maps are available in print form (Ref 2) or electronically via the Cambridge Materials Selector, a "Windows"-based PC tool-kit (available from Granta Design, Ltd., Cambridge, United Kingdom); examples of Ashby maps are provided in the article "Material Property Charts" in this Volume. Another approach using formal logic trees has been developed by Allen et al. (Ref 3) at Brigham Young University. At this stage the aim is to view potential materials as widely as possible and with a focus on just a few critical properties. Nominal values of key properties are sufficient, but costs should also be considered.

(ASM Handbook Volume 20 Materials selection and design, ASM INTERNATIONAL The Materials Information Company, p:1171)

Previous Definition: DRAFTING (Group: design)

After the preceding stages have been completed, the design is re produced by automated drafting machines for documentation and reference. At this stage, detailed and working drawings also are developed and printed. The CAD system also is capable of developing and drafting sactional view of part, scaling the drawings, and performing transformaions in order to present various views of the part. 
(Serope Kalpakjian, Steven R. Schimidt, MANUFACTORING ENGINEERING AND TECHNOLOGY, 5th Edition, page 1202)

New Definition: DRAFTİNG (Group: design)  (better)

Drafting and Product Documentation: Documenting products includes more than drafting. In addition to the detailed drawings that have traditionally been used to describe designs, other types of printed and drawn materials are produced. These include specifications, assembly and manufacturing instructions, maintenance manuals, user and instruction manuals, spare parts lists and drawings, and marketing materials among others. Solid models can be used to help prepare many types of drawings including exploded assemblies, perspective views, cutaway views, photo-realistic renderings, etc. These can be transferred into technical publication, page layout, Word processing, and art programs for inclusion in printed and electronic documents. With parametric solid modeling systems, dimensions in drawings can be generated automatically. Solids also provide automatic hidden-line removal, shaded-image views, and section views. Figure 10 illustrates an information-rich alternative to traditional drawings one that is based on having solid models.

Fig. 10 Detailed drawing with shaded views. Courtesy of Computervision

(ASM Handbook Volume 20 Materials selection and design, ASM INTERNATIONAL The Materials Information Company, p:384)