Engineering plastics, as a general class of materials, are prone to the development of internal stresses which arise during processing or during servicing when parts are exposed to environments that impose deformation and/or temperature extremes. Thermal stresses are largely a consequence of high coefficients of thermal expansion and low thermal diffusivities. Although time-consuming techniques can be used to analyze thermal stresses, several useful qualitative tests are described in this article. The classification of internal stresses in plastic parts is covered. The article describes the effects of low thermal diffusivity and high thermal expansion properties, and the variation of mechanical properties with temperature. It discusses the combined effects of thermal stresses and orientation that result from processing conditions. The article also describes the effect of aging on properties of plastics. It explains the use of high-modulus graphite fibers in amorphous polymers.

For the reinforcement of metal-matrix composites, four general classes of materials are commercially available: oxide fibers based primarily on alumina and alumina silica systems, nonoxide systems based on silicon carbide, boron fibers, and carbon fibers. This article discusses the key aspects of aluminum oxide fibers, silicon carbide fibers, boron fibers, and carbon fibers. The commercial fibers for reinforcement of metal-matrix composites are presented in a table. A tabulation of the coating schemes for silicon carbide monofilament fibers is also provided.

This article describes the manufacture, post-processing, fabrication, and properties of carbon-carbon composites (CCCs). Manufacturing techniques with respect to the processibility of different geometries of two-directional and multiaxial carbon fibers are listed in a table. The article discusses matrix precursor impregnants, liquid impregnation, and chemical vapor infiltration (CVI) for densification of CCCs. It presents various coating approaches for protecting CCCs, including pack cementation, chemical vapor deposition, and slurry coating. Practical limitations of coatings are also discussed. The article concludes with information on the mechanical properties of CCCs.

Fiber-matrix adhesion is a variable to be optimized in order to get the best properties and performance in composite materials. This article schematically illustrates fiber matrix interphase for composite materials. It discusses thermodynamics of interphase in terms of surface energy, contact angle, work of adhesion, solid surface energy, and wetting and wicking. The article describes the change in interphase depending on the reinforcing fiber such as glass fiber, polymeric fiber, and carbon fiber. It emphasizes fiber-matrix adhesion measurements by direct methods, indirect methods, and composite laminate tests. The effects of interphase and fiber-matrix adhesion on composite mechanical properties, such as composite on-axis properties, composite off-axis properties, and composite fracture properties, are also discussed.

The earliest commercial use of carbon fibers is often attributed to Thomas Edison's carbonization of cotton and bamboo fibers for incandescent lamp filaments. This article describes the manufacture of PAN-based carbon fibers and pitch-based carbon fibers. It discusses the properties and characteristics of carbon fibers in terms of axial structure, transverse structure, and interfacial bonding. The article discusses the typical applications of carbon fibers, including aerospace and sporting goods. It concludes with a discussion on anticipated developments in carbon fibers.

This article is a compilation of tables containing property data for major reinforcement materials, including high-modulus fibers, carbon fibers, graphite fibers, glass fibers, ceramic short fibers and whiskers. Data are provided for physical, mechanical, chemical, thermal and electrical properties of these materials. Maximum service temperatures of whisker reinforcements also are provided.

Carbon-carbon composites (CCCs) are introduced in fields that require their high specific strength and stiffness, in combination with their thermoshock resistance, chemical resistance, and fracture toughness, especially at high temperatures. The use of CCCs has expanded as the price of carbon fibers has dropped and their mechanical properties have increased. This article begins with an overview of the carbon conversion processes, fiber properties and microstructures, and interfacial bonding and environmental interaction of carbon fibers, followed by a detailed discussion on the various techniques available for processing CCCs for specific applications, including preform fabrication (fiber weaving), densification, application of protective coatings, and joining. The article closes with a description of the mechanical and physical properties and applications of CCCs. The main applications of CCCs, in terms of money and mass, are in the military, space, and aircraft industries.