This chapter discusses the ambient-temperature corrosion characteristics of aluminum metal-matrix composites (MMCs), including composites formed with boron, graphite, silicon carbide, aluminum oxide, and mica. It also discusses the effect of stress-corrosion cracking on graphite-aluminum composites and the use of protective coatings and design criteria for corrosion prevention.

Metal-matrix composites (MMCs) work at higher temperatures than their base metal counterparts and can be engineered for improved strength, stiffness, thermal conductivity, abrasion and/or creep resistance, and dimensional stability. This chapter examines the properties, compositions, and performance-cost tradeoffs of common MMCs, including aluminum-matrix composites, titanium-matrix composites, and fiber-metal laminates. It also explains how fiber-reinforced composites and laminates are made, describing both continuous and discontinuous fiber matrix production processes.

This chapter discusses the advantages and disadvantages of metal matrix composites and the methods used to produce them. It begins with a review of the composition and properties of aluminum matrix composites. It then describes discontinuous composite processing methods, including stir and slurry casting, liquid metal infiltration, spray deposition, powder metallurgy, extrusion, hot rolling, and forging. The chapter also provides information on continuous-fiber aluminum and titanium composites as well as particle-reinforced titanium and fiber metal (glass aluminum) laminates.

This chapter discusses the extrusion characteristics of hard aluminum alloys, particularly those in the 5000 and 7000 series. It begins with a review of two studies, one showing how the extrudability of 7 xxx alloys varies with the presence and amount of different alloying elements, the other relating minimum wall thickness with circumscribing circle diameter. It then explains how oxides on either the billet or container complicate the control of extrusion as well as auxiliary processes and how material flow and the movement of trapped gasses in different regions of the extrusion can lead to defects and variations in strength. It also discusses the extrusion of aluminum matrix composites and explains how composite billets are made.

This chapter reviews and provides data tables for the wide range of properties and performance characteristics that are possible with specific aluminum casting alloys and tempers. Properties and performance attributes addressed include casting and finishing characteristics; typical physical properties; typical and minimum (design) mechanical properties; fatigue strength; fracture resistance, including subcritical crack growth; and resistance to general corrosion and to stress-corrosion cracking. The chapter concludes with information on the properties of cast aluminum matrix composites.

Metal-matrix composites can operate at higher temperatures than their base metal counterparts and, unlike polymer-matrix composites, are nonflammable, do not outgas in a vacuum, and resist attack by solvents and fuels. They can also be tailored to provide greater strength and stiffness, among other properties, in preferred directions and locations. This chapter discusses the processes and procedures used in the production of fiber-reinforced aluminum and titanium metal-matrix composites. It explains how the length and orientation of reinforcing fibers affect the properties and processing characteristics of both aluminum and titanium composites. It also provides information on fiber-metal laminates and the use of different matrix metals and reinforcing materials.

Engineers have many materials to choose from when dealing with weight-related design constraints. The list includes aluminum, beryllium, magnesium, and titanium alloys as well as engineering plastics, structural ceramics, and polymer-, metal-, and ceramic-matrix composites. This chapter provides a brief overview of these lightweight materials, discussing their primary advantages along with their properties, behaviors, and limitations.

This chapter covers the basic aspects of composite materials. It describes the arrangement, form, and function of their constituent materials and explains how they perform better in combination than on their own. It discusses the directional nature of isotropic, anisotropic, and orthotropic materials, the orientation of plies in unidirectional (lamina) and quasi-isotropic (laminate) lay-ups, and the dominant role of fibers in determining strength, stiffness, and other lamina properties. The chapter also compares the engineering attributes of composites with those of metals and includes application examples.

This chapter discusses the types of fibers and matrix materials used in ceramic matrix composites and the role of interfacial coatings. It describes the methods used to produce ceramic composites, including powder processing, slurry infiltration and consolidation, polymer infiltration and pyrolysis, chemical vapor infiltration, directed metal oxidation, and liquid silicon infiltration.

Lightning damage in polymer composites, as in metal structures, is manifested by damage at both the macroscopic or visual level and within the material microstructure. In addition to visual damage assessment, non-destructive inspection techniques are employed to detect damage within the composite part. This chapter describes the macroeffects of a lightning strike on composites and discusses the methods involved in the assessment of microstructural damage in composites.

This chapter discusses the basic principles of precipitation hardening, an important strengthening mechanism in nonferrous alloys as well as stainless steel. It begins with a detailed review of the theory of precipitation hardening, then describes its application to aluminum alloys and nickel-base superalloys.

This chapter describes the conditions under which environmental degradation is likely to occur in polymer matrix composites and the potential damage it can cause. It discusses the problems associated with moisture absorption and exposure to solvents, fuels, ultraviolet radiation, lightning strikes, thermal oxidation, and extreme temperatures. It also discusses the factors that influence flammability.