Glass matrix composites, dispersion-reinforced mechanical properties

The development of dispersion reinforced glass matrix composites with improved mechanical properties for structural applications was first reported in 1962 [1]. Since then, hundreds of composite systems have been developed by incorporating a great variety of... 

Table 1 shows a compilation of typical mechanical properties of different glass-containing composite systems discussed above. The properties should be compared with those of traditional glass and glass-ceramic matrix composites with dispersion or fibre reinforcement, discussed in Chapters 20 and 19, respectively. Although the principal effort has been in developing composites with improved mechanical properties, in particular fracture... 

Fiber-reinforced plastics are the most successful composite materials. In spite of the poor load-bearing ability of polymeric materials, excellent mechanical properties are achieved by using fiber architectures of glass and carbon hbers in a manner similar to the reinforcement of concrete with steel rods and frames. For example, toughened polymeric materials with dispersed rubber particles in a polymer matrix exhibit high fracture energy. In composite materials, introduction of secondary materials into the matrix can improve the mechanical properties considerably. 

Polyimide characterised by thermal and thermal-oxidative stability at elevated temperatures, chemical resistance and good mechanical properties is relatively new in the family of polymer foams [3]. In some cases, depending on the nses, additional reinforcement can be inclnded. Examples are fibre reinforced foams and syntactic foams which are composites containing hollow glass, ceramic or plastic micro-spheres dispersed throughout the polymer matrix. 

The reinforcement of polypropylene and other thermoplastics with inorganic particles such as talc and glass is a common method of material property enhancement. Polymer clay nanocomposites extend this strategy to the nanoscale. The anisometric shape and approximately 1 nm width of the clay platelets dramatically increase the amount of interfacial contact between the clay and the polymer matrix. Thus the clay surface can mediate changes in matrix polymer conformation, crystal structure, and crystal morphology through interfacial mechanisms that are absent in classical polymer composite materials. For these reasons, it is believed that nanocomposite materials with the clay platelets dispersed as isolated, exfoliated platelets are optimal for end-use properties. 

Composite materials have a bulk phase, which is continuous, called the matrix, and one or more dispersed, noncontinuous phases, called the reinforcement, which usually has superior mechanical or thermal properties to the matrix. The region tetween the two can be simply a surface, called an interface, or a third phase, called an interphase. An example of the latter is a layer of coupling agent coated on glass fibers that facilitates adhesion of the glass to the matrix polymer. 

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