Composites classification scheme

Figure 13.1. Polymer composite classification scheme. (Sperling, 914d.)...

A classification by chemical type is given ia Table 1. It does not attempt to be either rigorous or complete. Clearly, some materials could appear ia more than one of these classifications, eg, polyethylene waxes [9002-88 ] can be classified ia both synthetic waxes and polyolefins, and fiuorosihcones ia sihcones and fiuoropolymers. The broad classes of release materials available are given ia the chemical class column, the principal types ia the chemical subdivision column, and one or two important selections ia the specific examples column. Many commercial products are difficult to place ia any classification scheme. Some are of proprietary composition and many are mixtures. For example, metallic soaps are often used ia combination with hydrocarbon waxes to produce finely dispersed suspensions. Many products also contain formulating aids such as solvents, emulsifiers, and biocides. 

The basic nature of composite materials was introduced in Chapter 1. An overall classification scheme was presented, and the mechanical behavior aspects of composite materials that differ from those of conventional materials were described in a qualitative fashion. The book was then restricted to laminated fiber-reinforced composite mafeffals. The basic definitions and how such materials are made were then treated. Finally, the current and potential advantages of composite materials were discussed along with some case histories that clearly reveal how composite materials are used in structures. 

In the method of classification of matter based on composition, a given specimen of material is regarded as either a pure substance or a mixture. An outline of this classification scheme is shown in Table 1-2. The term pure substance (or merely substance) refers to a material all parts of which have the same composition and which has a definite and unique set of properties. In contrast, a mixture consists of two or more substances and has a somewhat arbitrary composition. The properties of a mixture are not unique, but depend on its composition. The properties of a mixture tend to reflect the properties of the substances of which it is composed that is, if the composition is changed a little, the properties will change a little. 

Each of these solid phases can be described in terms of their mineralogy. This classification scheme is based on crystal structure and chemical composition. The most common minerals found in marine sediments are listed in Table 13.2. Most are silicates in which Si and O form a repeating tetrahedral base unit. Other minerals common to marine sediments are carbonates, sulfates, and oxyhydroxides. Less common are the hydrogenous minerals as they form only in restricted settings. These include the evap-orite minerals (halides, borates, and sulfates), hydrothermal minerals (sulfides, oxides, and native elements, such as gold), and phosphorites. 

Regardless, the classification system should achieve a specific outcome and add value. To achieve this goal, companies should consider developing a classification scheme that helps establish the proper team composition based on the complexity, nature, and severity of the occurrence. Chapter 7 describes considerations for building a team based on classification of an incident. The chapter defines terms such as minor incidents, limited impact incidents, significant incidents, high-potential incidents (HIPO), and catastrophic incidents. 

One alternative classification scheme simply specifies the experience level of the lead investigator and then leaves the team composition to the leader. This approach depends upon the leader s experience and training. 

There are many ways to classify composites, including schemes based upon (1) materials combinations, such as metal-matrix, or glass-fiber-reinforced composites (2) bulk-form characteristics, such as laminar composites or matrix composites (3) distribution of constituents, such as continuous or discontinuous or (4) function, like structural or electrical composites. Scheme (2) is the most general, so we will utilize it here. We will see that other classification schemes will be useful in later sections of this chapter. 

In Section 1.4.2, we described several classification schemes for composites, including one that is based upon the distribution of the constituents. For reinforced composites, this scheme is quite useful, as shown in Figure 1.75. In reinforced composites, the reinforcement is the structural constituent and determines the internal structure of the composite. The reinforcement may take on the form of particulates, flakes, lamina, or fibers or may be generally referred to as filler. Fibers are the most common type of reinforcement, resulting in fiber-matrix composites (FMCs). Let us examine some of these reinforcement constituents in more detail. 

Aerosol Instrument Classification. Friedlander (34) classified the range of aerosol instrumentation in terms of resolution of particle size, time, and chemical composition. This classification scheme is illustrated in Figure 3. The ideal instrument would be a single-particle counter-sizer-analyzer. Operating perfectly, this mythical instrument would fully characterize the aerosol, with no lumping of size or composition classes, and would make such measurements sufficiently rapidly to follow any transients occurring in the aerosol system. 

The most common classification scheme in electrophoresis focuses on the nature of electrolyte system. Using this scheme, electrophoretic modes are classified as continuous or discontinuous systems. Within these groupings the methods may be further divided on the basis of constancy of the electrolyte if the composition of the background electrolyte is constant as in capillary zone electrophoresis, the result is a kinetic process. If the composition of the electrolyte is not constant, as in isoelectric focusing, the result is a steady-state process. 

The classification scheme is based on discharge residue particles from modern primed brass-cased ball ammunition. It is only applied rigidly when no other information is available. When a gun, ammunition, spent cartridge case, or bullet is recovered, it can be examined to determine elemental composition and likely discharge residue particle composition. 

This review is intended to focus on ceramic matrix composite materials. However, the creep models which exist and which will be discussed are generic in the sense that they can apply to materials with polymer, metal or ceramic matrices. Only a case-by-case distinction between linear and nonlinear behavior separates the materials into classes of response. The temperature-dependent issue of whether the fibers creep or do not creep permits further classification. Therefore, in the review of the models, it is more attractive to use a classification scheme which accords with the nature of the material response rather than one which identifies the materials per se. Thus, this review could apply to polymer, metal or ceramic matrix materials equally well. 

Besides the classification of the elements and compounds, there are related chemical systems that illustrate the intricacies and not quite hierarchical structure of scientific classification schemes. Molecular systems that crystallize are further classified by crystal structure. Organic molecules have an elaborate system of classification called "nomenclature" based on both their chemical composition and their symmetries. The classifications are correlated with properties that do not define the classification. Thus, the classification of the elements is associated with a numerical property—atomic weight—and molecular symmetries are associated with optical activity. What are the formal structures that make multiple classifications correct, and how does the existence of one classification scheme constrain others What is the purpose, methodological or otherwise, of corresponding properties Chemistry provides our most familiar examples of settled scientific classifications, and when we want to know what makes for such certainty, chemistry is where we should look. 

Within the last several years HPLC separations have been optimized in terms of the most appropriate mobile phase composition for a particular set of solutes by exploring the whole plane of solvent selectivities using this solvent classification scheme with a minimal number of measurements in statistically-designed experiments. For reversed phase HPLC systems, the selectivity triangle is often defined by methanol, acetonitrile, and tetrahydrofuran with water as the diluent (37). 

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