This chapter provides a general description of materials and methods for manufacturing high-performance composites. The materials covered are polymer matrices and prepreg materials and the methods include infusion processes, composite-toughening methods, matrix-toughening methods, and dispersed-phase toughening. In addition, the chapter provides information on interlayer-toughened composites and honeycomb or foam structure composite materials. It also discusses the processes in optical microscopy of composite materials.

The second-generation composite materials were added to increase the strain to failure of the primary phase and/or create a dispersed second phase, thereby enhancing the fracture toughness of the thermosetting matrix. These matrices offered novel design capabilities for composites in a variety of aircraft applications. To improve the damage tolerance of composite materials even further, an engineering approach to toughening was used to modify the highly stressed interlayer with either a tougher material or through the use of preformed particles, leading to the third generation of composite materials. This chapter discusses the development, processes, application, advantages, and disadvantages of dispersed-phase toughening of thermoset matrices. Information on the processes of particle interlayer toughening of composite materials is also included.

Polymer composite materials are subject to degradation if not appropriately protected from the environment. Composite materials having polymeric matrices are susceptible to degradation from heat, sunlight, ozone, atomic oxygen (in space), moisture, solvents (chemicals), fatigue, excessive loading, and combinations of these environmental conditions. This chapter discusses the effects of heat, ultraviolet-light, and atomic oxygen on composite materials.

The analysis of composite materials using optical microscopy is a process that can be made easy and efficient with only a few contrast methods and preparation techniques. This chapter is intended to provide information that will help an investigator select the appropriate microscopy technique for the specific analysis objectives with a given composite material. The chapter opens with a discussion of macrophotography and microscope alignment, and then goes on to describe various illumination techniques that are useful for specific analysis requirements. These techniques include bright-field illumination, dark-field illumination, polarized-light microscopy, interference and contrast microscopy, and fluorescence microscopy. The chapter also provides a discussion of sample preparation materials such as dyes, etchants, and stains for the analysis of composite materials using optical microscopy.

Microstructural analysis of the composite matrix is necessary to understand the performance of the part and its long-term durability. This chapter focuses on the microstructural analysis of engineering thermoplastic-matrix composites and the influence of cooling rate and nucleation on the formation of spherulites in high-temperature thermoplastic-matrix carbon-fiber-reinforced composites. It also describes the microstructural analysis of a bio-based thermosetting-matrix natural fiber composite system.

This chapter discusses the properties and uses of fiber-reinforced composites. It also describes the effect of volume fraction and fiber length.

This chapter discusses the use of thermoset and thermoplastic resins in polymer matrix composites. It begins by explaining how the two classes of polymer differ and how it impacts their use as matrix materials. It then goes on to describe the characteristics of polyester, vinyl ester, epoxy, bismaleimide, cyanate ester, polyimide, and phenolic resins and various toughening methods. The chapter also covers thermoplastic matrix materials and product forms and provides an introduction to the physiochemical tests used to characterize resins and cured laminates.

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.

Ceramic-matrix composites possess many of the desirable qualities of monolithic ceramics, but are much tougher because of the reinforcements. This chapter explains how reinforcements are used in ceramic-matrix composites and how they alter energy-dissipating mechanisms and load-carrying behaviors. It compares the stress-strain curves for monolithic ceramics and ceramic-matrix composites, noting improvements afforded by the addition of reinforcements. It then goes on to discuss the key attributes, properties, and applications of discontinuously reinforced ceramic composites, continuous fiber ceramic composites, and carbon-carbon composites. It also describes a number of ceramic-matrix composite processing methods, including cold pressing and sintering, hot pressing, reaction bonding, directed metal oxidation, and liquid, vapor, and polymer infiltration.

The formation of microcracks in composite materials may arise from static-, dynamic-, impact-, or fatigue-loading situations and also by temperature changes or thermal cycles. This chapter discusses the processes involved in the various methods for the microcrack analysis of composite materials, namely bright-field analysis, polarized-light analysis, contrast dyes analysis, and dark-field analysis. The analysis of microcracked composites using epi-fluorescence is also covered. In addition, the chapter describes the procedures for the determination and recording of microcracks in composite materials.

This article focuses on characterization techniques used for analyzing the physical behavior and chemical composition of thermoset resins, namely chromatography and infrared spectroscopy. The main purpose is to give sufficient detail to permit the reader understand a particular test technique and its value to the thermoset resin field. Epoxy resins are emphasized in the examples because they dominate the airframe and aerospace industries. The article also provides information on two categories of characterization of the processing behavior of thermoset. The first studies the thermal properties of reactive thermoset systems, while the second utilizes these thermal characteristics as the basis for monitoring and control during processing.

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.

Specimen preparation is the first step that determines the quality of the microstructural information that can be obtained using optical microscopy. This chapter describes the sample preparation methods that are applicable to most types of composite materials containing short discontinuous or continuous fibers. The sample preparation methods cover documentation and labeling of samples, sectioning the composite, clamp-mounting composite samples, mounting composite samples in casting resins, and the addition of contrast dyes to casting resins. Information on the molds used for mounting composite materials is provided. The steps recommended to achieve a good mounted specimen without voids or specimen pull-out are also described. The chapter discusses the processes for clamping mounted composite samples in automated polishing heads and mounting composite materials for hand polishing. A summary of the mounting technique is also included.

In an attempt to explain the stresses encountered in the plastics industry, this article first defines the different types of internal stresses in amorphous polymers. Each type of thermal stress is then discussed in detail, with reference to the mechanism of generation and the effect on engineering properties. Methods of detecting and measuring internal stresses are also presented. The article then describes the combined effects of thermal stresses and orientation that result from processing conditions. Finally, it discusses numerous aspects of physical aging and the use of high-modulus graphite fibers in amorphous polymers.

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.

The most common methods for preparing polymeric composites for microscopic analysis can be used for most fiber-reinforced composite materials. There are, however, a few composite materials that require special preparation techniques. This chapter discusses the processes involved in the preparation of titanium honeycomb composites, boron fiber composites, titanium/polymeric composite hybrids, and uncured prepreg materials.

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.

This article describes in more detail the fundamental building-block level, atomic, then expands to a discussion of molecular considerations, intermolecular structures, and finally supermolecular issues. An explanation of important thermal, mechanical, and physical properties of engineering plastics and commodity plastics follows, and the final section briefly outlines the most common plastics manufacturing processes.

This article briefly reviews abrasive and adhesive wear failure of reinforced polymers and polymer composites, namely particulate-filled polymers, short-fiber-reinforced polymers, polymers with continuous fibers, and mixed reinforcements and fabrics. It includes scanning electron microscope micrographs of abraded surfaces of composites against 80-grade SiC paper and under 14 N load, and worn surfaces of abraded polyether-imide composites and polyamide 66 unidirectional composites and 66 hybrid composites.