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.

The selection of engineered materials is an integrated process that requires an understanding of the interaction between materials properties, manufacturing characteristics, design considerations, and the total life cycle of the product. This article classifies various engineered materials, including ferrous alloys, nonferrous alloys, ceramics, cermets and cemented carbides, engineering plastics, polymer-matrix composites, metal-matrix composites, ceramic-matrix and carbon-carbon composites, and reviews their general property characteristics and applications. It describes the synergy between the elements of the materials selection process and presents a general comparison of material properties. Finally, the article provides a short note on computer aided materials selection systems, which help in proper archiving of materials selection decisions for future reference.

Coating technology for carbon-carbon has been driven primarily by the aerospace and defense industries, in applications where the composite is exposed to high-temperature oxidizing environments. The most notable application of coated carbon-carbon is for the nose cap and wing leading edges of the Shuttle Orbiter vehicle. This article details the fundamentals of protecting carbon-carbon composites. It explains various coating deposition techniques: pack cementation, chemical vapor deposition, and slurry coatings. The article discusses typical coating architectures in accordance with the process used to deposit the primary oxygen barrier. It also provides information on the practical limitations of coatings for the composites.

This article introduces the principal methodologies and some advanced technologies that are being applied for nondestructive evaluation (NDE) of fiber-reinforced polymer-matrix composites. These include acoustic emission, ultrasonic, eddy-current, computed tomography, electromagnetic acoustic transducer, radiography, thermography, and low-frequency vibration methods. The article also provides information on NDE methods commonly used for metal-matrix composites.

This article discusses the types, properties, and uses of continuous-fiber-reinforced composites, including glass, carbon, aramid, boron, continuous silicon carbide, and aluminum oxide fiber composites. While polyester and vinyl ester resins are the most used matrix materials for commercial applications, epoxy resins, bismaleimide resins, polyimide resins, and thermoplastic resins are used for aerospace applications. The article addresses design considerations as well as product forms and fabrication processes.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of a type of resin-matrix composites, carbon-epoxy composites. The fractographs illustrate the fracture modes found in composite prepregs, composite panels, solid rocket motor nozzles, and tension, flexural, compressive, and shear loadings.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of metal-matrix composites, including tungsten fiber-reinforced aluminum, tungsten fiber-reinforced carbon steel, and tungsten fiber-reinforced silver. The fractographs illustrate the ductile fracture, interlaminar failure, transgranular cleavage and fracture, tension-overload fracture, longitudinal and transverse cracking, fiber splitting, stress rupture, and low-cycle fatigue of these composites.

Ceramic-matrix composites (CMCs) are being developed for a number of high-temperature and high-performance applications in industrial, aerospace, and energy conservation sectors. This article focuses on processing, fabrication, testing, and characterization methods of CMCs, namely, discontinuously reinforced composites and continuous-fiber-reinforced composites. Processing methods include cold pressing, sintering, hot pressing, reaction bonding, melt infiltration, directed metal oxidation, sol-gel and polymer pyrolysis, self-propagating high-temperature synthesis and joining. A table summarizes the properties of various ceramic reinforcements and industrial applications of these composites.

Metal-matrix composites (MMCs) are a class of materials with potential for a wide variety of structural and thermal applications. This article discusses the mechanical properties of MMCs, namely aluminum-matrix composites, titanium-matrix composites, magnesium-matrix composites, copper-matrix composites, superalloy-matrix composites, and intermetallic-matrix composites. It describes the processing methods of discontinuous aluminum MMCs which include casting processes, liquid-metal infiltration, spray deposition and powder metallurgy. The article provides useful information on aluminum MMC designation system and also describes the types of continuous fiber aluminum MMCs, including aluminum/boron MMC, aluminum/silicon carbide MMC, aluminum/graphite MMC, and aluminum/alumina MMC.

This article begins with the discussion on the background of metal-matrix composites (MMC) and moves into a broad description of the general parameters affecting the corrosion of MMC. It discusses the primary sources of MMC corrosion that include galvanic corrosion between MMC constituents, chemical degradation of interphases and reinforcements, microstructure-influenced corrosion, and processing-induced corrosion. The article elaborates on the corrosion behavior of specific aluminum, magnesium, titanium, copper, stainless steel, lead, depleted uranium, and zinc MMCs systems. It concludes with a description on the corrosion control of MMCs using protective coatings and inhibitors.

This article discusses the solidification of matrix alloy in cast metal matrix composites (MMCs). It begins with a discussion on the mixing techniques in reinforcement incorporation and wettability of reinforcement. It describes the solidification processes, such as stir mixing and melt infiltration, used in the synthesis of MMCs. The article also discusses the fundamentals of solidification process and presents a computational modeling of particle/solidification front interactions in metal-ceramic systems. The article concludes with information on nanocomposites.

Metal matrix composites (MMCs) can be synthesized by vapor phase, liquid phase, or solid phase processes. This article emphasizes the liquid-phase processing where solid reinforcements are incorporated in the molten metal or alloy melt that is allowed to solidify to form a composite. It illustrates the three broad categories of MMCs depending on the aspect ratio of the reinforcing phase. The categories include continuous fiber-reinforced composites, discontinuous or short fiber-reinforced composites, and particle-reinforced composites. The article discusses the two main classes of solidification processing of composites, namely, stir casting and melt infiltration. It describes the effects of reinforcement present in the liquid alloy on solidification. The article examines the automotive, space, and electronic packaging applications of MMCs. It concludes with information on development of select cast MMCs.

The structural efficiency of a composite structure is established by its joints and assembly. Adhesive bonding, mechanical fastening, and fusion bonding are three types of joining methods for polymer-matrix composites. This article provides information on surface treatment and the applications of adhesive bonding. It discusses the types of adhesives, namely, epoxy adhesives, epoxy-phenolic adhesives, condensation-reaction PI adhesives, addition-reaction PI adhesives, bismaleimide adhesives, and structural adhesives. The article provides information on fastener selection considerations, including corrosion compatibility, fastener materials and strength, head configurations, importance of clamp-up, interference fit fasteners, lightning strike protection, blind fastening, and sensitivity to hole quality. Types of fusion bonding are presented, namely, thermal welding, friction welding, electromagnetic welding, and polymer-coated material welding.

This article describes the use of conventional machining techniques, laser cutting and water-jet cutting for producing finished composite parts. It explains two representative polymer-matrix composites--graphite and aramid composites--and discusses the machining and drilling problems such as delamination and fiber or resin pullout. The article describes machining and drilling techniques and the necessary tools and cutting parameters. It presents a description of laser cutting. The article also provides information on the advantages, disadvantages, cutting characteristics, and applications of water-jet cutting and abrasive water-jet cutting.

Tensile testing of fiber-reinforced composite materials is performed to determine uniaxial tensile strength, Young’s modulus, and Poisson’s ratio relative to principal material directions, and helps in the prediction of the properties of laminates. Beginning with an overview of the fundamentals of tensile testing of fiber-reinforced composites, this article describes environmental exposures that can occur during specimen preparation and testing. These include exposures during specimen preparation, and planned exposure such as moisture, damage (impact), and thermal cycling. The article also discusses the test methods of the four major types of mechanical testing of polymer-matrix composites: tensile, compression, flexural, and shear.

Ultrasonic inspection is a nondestructive technique that is useful in both quality control and research applications for flaw detection in fiber-reinforced composite materials. This article describes ultrasonic nondestructive analysis by outlining its three basic types of scans. It reviews the important quality control techniques used during the manufacture of composite components by analyzing tooling control, material control, pattern orientation control, and in-process control.

This article describes the four major conditions that can cause beryllium to corrode in air. These include beryllium carbide particles exposed at the surface; surface contaminated with halide, sulfate, or nitrate ions; surface contaminated with other electrolyte fluids; and atmosphere that contains halide, sulfate, or nitrate ions. The article provides information on the behavior of beryllium under the combined effects of high-purity water environment, stress and chemical environment, and high-temperature environment. The compositions of the structural grades for intentionally controlled elements and major impurities are tabulated. The article discusses in-process problems and procedures with beryllium and aluminum-beryllium composites to prevent corrosion during processing, handling, and storage. It also describes the types of coatings used on beryllium and aluminum-beryllium. These include chemical conversion coatings, anodized coatings, plated coatings, organic coatings, and plasma-sprayed coatings.

Relatively limited effort has gone into developing repair processes and materials for composites, in contrast to the significant labor and expense that has gone into the development of these materials for numerous critical applications. As composites gain wider acceptance as aerospace materials, there is a need to understand the requirements of the end users regarding repair of these advanced materials. This article focuses on the repair of graphite-epoxy structures designed in a variety of forms for a wide range of load intensities. Five repair concepts developed for generic laminate repair have been validated in this article through the required environmental and load condition tests. These include bonded-scarf joint flush repair, double-scarf joint flush repair, blind-side banded-scarf repair, blind-side sandwich repair, and bonded external patch repair. A brief note on thermoplastic repair concepts is also provided in this article.

This article describes the resin and fabrication requirements associated with fiberglass-reinforced plastic equipment. It provides a discussion on various resins and their resistance to various environments. These include polyester, epoxy, epoxy vinyl-ester, and furan and phenolic thermosetting resins. The article concludes with a discussion on the curing system of the thermosetting resins with a wide variety of hardener types.