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.

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.

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 presents the fundamentals of tensile testing of fiber-reinforced polymer composites. Basic tensile testing of polymer composites is divided into lamina and laminate testing. The chapter focuses on tensile testing of laminates. It discusses the most common tensile test methods that have been standardized for fiber-reinforced composite materials. It also briefly reviews considerations in tensile testing of metal-matrix composites.

Composite systems for cryogenic applications are discussed in this chapter. This chapter emphasizes filamentary-reinforced composites because they are the most widely used composite materials. It begins with a discussion on the approach to designing and fabricating with low-pressure laminate composites. This is followed by a section providing an overview of the materials in modern cryogenic technology. Then, the chapter describes the effect of cryogenic temperatures on materials properties; it also introduces the various joining techniques developed for composite materials. The effects of radiation on the properties of the materials are covered as well as the processes involved in testing laminates at cryogenic temperatures. Finally, the chapter provides information available on concrete aggregate composites.

Unlike metals, in which fatigue failures are due to a single crack that grows to a critical length, the effects of fatigue in composites are much more distributed and varied. As the chapter explains, there are five major damage mechanisms that contribute to the progression of composite fatigue, those being matrix cracking, fiber breaking, crack coupling, delamination initiation, and delamination growth. The chapter describes each mechanism in detail along with related factors. It also discusses the primary differences between composites and metals, the effect of manufacturing defects, damage tolerance, and testing and certification.

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 failure mechanisms associated with fiber-reinforced composites. It begins with a review of fiber-matrix systems and the stress-strain response of unidirectional lamina and both notched and unnotched composite laminate specimens. It then explains how cyclic loading can lead to delamination, the primary failure mode of most composites, and describes some of the methods that have been developed to improve delamination resistance, assess damage tolerance, determine residual strength, and predict failure modes.

This chapter discusses design and certification considerations, including materials and process selection, the building block approach to certification, design allowables, and design guidelines. It also includes information on damage tolerance and environmental sensitivity.

This article depicts typical fractographic features for a number of different composite materials, covering interlaminar and translaminar fracture characteristics in composite materials.

This chapter provides an overview of the tools and techniques, as well as some of the underlying theory, that have proven useful for process modeling and simulation. It begins by presenting the framework of a thermoset cure model that accounts for kinetics, viscosity, heat transfer, flow, voids, and residual stress. It then discusses each variable in detail, explaining how it affects the cure process, how it is measured, and how it can be expressed mathematically in the form of a simple model. The discussions throughout the chapter are supported by numerous images, diagrams, and data plots.

This chapter examines the static, fatigue, and damage tolerance properties of glass, aramid, and carbon fiber systems. It also explains how delaminations, voids, porosity, fiber distortion, and fastener hole defects affect impact resistance and strength.

This chapter discusses composite testing procedures, including tension, compression, shear, flexure, and fracture toughness testing as well as adhesive shear, peel, and honeycomb flatwise tension testing. It also discusses specimen preparation, environmental conditioning, and data analysis.

The objective of mechanical testing of an engineered material is to provide data necessary for the analysis, design, and fabrication of structural components using the material. The testing of filament-wound composite materials offers unique challenges because of the special characteristics of composites. This chapter describes suitable static mechanical test techniques for characterizing laminated composite materials. The approach is to provide recommended techniques, based on consensus opinions of fabricators and users of filament-wound composites, and to survey available techniques that have been used successfully in the field. The chapter describes the effects of various factors on the properties of composite constituents, including fibers, resins, and unidirectional plies. Some aspects of specimen selection are also described. The chapter provides information on pressure bottles and tubular parts that have been developed as standard test specimens for combined load testing of composites.

This chapter discusses the use of mechanical fastening and adhesive bonding, the primary methods for joining polymer matrix composites. It describes and analyzes the basic types of mechanically fastened joints, including single-hole and multirow bolted composite joints. It then reviews the advantages and disadvantages of adhesively bonded joints and compares and contrasts the long-term performance of various joint designs. The chapter also discusses the merits of stepped-lap and bonded-bolted joints.

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.

This chapter discusses some of the challenges associated with the analysis of composite structures. It begins with a review of lamina fundamentals and the stress-strain relationships in a single ply under various types of loads. It demonstrates the use of classical lamination theory, discusses the effects of interlaminar free-edge stresses, and explains how to predict the failure of composites using stress and strain criteria as well as the Azzi-Tsai-Hill maximum work theory and the Tsai-Wu failure criterion.

Polymer-matrix composites are among the lightest structural materials in use today. They are also highly resistant to corrosion and fatigue and their load-carrying capabilities, such as strength and stiffness, can be tailored for specific applications. This chapter discusses the primary advantages and disadvantages of polymer-matrix composites, how they are produced, and how they perform in different applications. It describes the construction of laminates, the fibers and resins used, and the methods by which they are combined. It explains how strength, modulus, toughness, and high-temperature and corrosion behaviors are determined by the orientation, shape, and spacing of fibers, the number of plies, resin properties, and consolidation and forming methods. The chapter also covers secondary fabrication processes, such as thermoforming, machining, and joining, as well as production equipment and product forms, and include guidelines for optimizing tradeoffs when selecting fibers, resins, and production techniques.