Maintainability is a function of the durability, damage tolerance, and repairability of a structure. This article discusses the configurations of composite structures, such as sandwich, stiffened-skin, and monolithic structures, used in commercial aircraft composites. It describes the considerations for maintainability of the composite structures during the conceptual design phase. Sources of the defects and damage, such as manufacturing defects and in-service defects, are reviewed. The article describes the nondestructive inspection methods that are used in the repair of composite structures to locate damage, characterize the extent of damage, and ensure post-repair quality. It lists suggestions that can be used as design guidelines for adhesive bonding, general composite structure, sandwich structure, material selection, and lightning-strike protection. The article also provides the basic considerations for personnel, facilities, and equipment during maintenance.

This article focuses on the monolithic form of nonferrous alloys, including aluminum, copper, nickel, cobalt, titanium, zinc, magnesium, and beryllium alloys. Each metal and alloy offers unique combinations of useful physical, chemical, and structural properties that are made available by its particular composition and the proper choice of processing method. The article describes the composition, designation system, properties, and processing method of these metals and alloys. It discusses the effect of alloying elements in these alloys. The article explains microstructure/property relationships that are used to make specific properties available to the designers of structural applications. It provides examples of phase diagrams that illustrate eutectic and peritectic reactions.

Inorganic chemical-setting ceramic linings are one of the most widely used construction materials in designing the protective linings for industrial installations. Monolithic linings can be applied by cast or gunite (shotcreting) methods over steel or concrete as well as brick and mortar masonry. This article provides a discussion on the function of monolithic linings, the advantages of these materials, the types of applications in which these materials can be successfully used, and the limitations of these linings. It describes the application procedures that should be followed to ensure proper installation of a dual-lining system. The industrial applications that illustrate the corrosion resistance and some uses of monolithic linings, as well as other applications in wastewater treatment systems and the chemical industry, are discussed.

Honeycomb-cored sandwich panels increase part stiffness at a lower weight than monolithic composite materials. This article illustrates an area of a honeycomb-cored sandwich structure composite cross section that is viewed using transmitted polarized light. This area shows the differences in the constituents and resin intermingling. The article discusses the factors that govern the honeycomb core movement and honeycomb core crush, with illustrations. Some common tests performed on honeycomb composites to characterize the skin-to-core bond strength are the climbing drum peel and flatwise tensile tests. The article concludes with a description on the reasons for core failure, which are analyzed after these tests.

The chemical process being catalyzed should have a high productivity within a specified reactor volume with high reaction rates for the desired reactions and low rates for undesired reaction pathways. This article reviews the general catalyst preparation procedures, namely, impregnation, ion exchange, and precipitation. Catalyst carriers are usually high-surface-area inorganic materials with complex pore structures, into which catalytic materials such as palladium, platinum, cobalt, chromium oxide, and vanadium pentoxide are deposited using these procedures. The article also provides information on catalyst powder processing.

Interpretation of failures of ceramic-matrix composites, and in particular continuous fiber reinforced ceramic-matrix composites is complicated by the complex structure of the composite material. This article describes the failure characteristics and evidence of failure mechanisms of these composites, with illustrations.

Traditional ceramics, one of two general classes, are commonly used in high-volume manufacturing to make building materials, household products, and various industrial goods. Although there is a tendency to equate traditional ceramics with low technology, sophisticated processes and advanced manufacturing techniques are often used where these materials are employed. This article examines several traditional ceramics, including structural clay, whiteware, glazes, enamels, portland cements, and concrete. It also provides a detailed account of fabrication methods, properties, and applications. As an example, common applications for structural clay include facing materials, load-bearing units, pavers, and ceramic tiles.

This article introduces the concepts of linear-elastic fracture mechanics (LEFM) and elastic-plastic fracture mechanics (EPFM). It reviews the fracture mechanics of ceramics and ceramic matrix composites (CMCs). The article describes some fracture toughness measurement techniques used on ceramics and CMCs: single edge notch bending, compact tension, double cantilever beam testing, chevron notch methods, and double torsion. It presents descriptions organized by their specimen types, and includes the advantages and disadvantages, as well as the experimental control schemes employed for each specimen type.

This article begins with a general review of the effects of changes in stress state on processing of materials. It describes the fundamentals of hydrostatic extrusion and reviews the various issues and benefits associated with hydrostatic extrusion. The article discusses the hydrostatic extrusion of structural alloys, composites, brittle materials, and intermetallics or intermetallic compounds, with examples. It concludes with a discussion on the attempts made to extend the hydrostatic extrusion to higher temperatures.

In the friction surfacing process, a rotating consumable is brought into contact with a moving substrate, which results in a deposited layer on the substrate. This article describes the process as well as the equipment used. It also provides information on the applications of the friction surface process.

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.

The applications of discontinuously reinforced ceramic-matrix composites (CMCs) fall into four major categories, namely, cutting tool inserts; wear-resistant parts; aerospace and military applications; and other industrial applications, including engines and energy-related applications. This article provides examples for these four categories, with an emphasis on those applications/materials that have achieved commercial viability. The applications for continuous fiber ceramic composites are also summarized.

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 mechanisms for enhancing the reliability of three types of ceramic-matrix composites: discontinuously reinforced ceramic-matrix composites, continuous fiber ceramic composites, and carbon-carbon composites. It also presents examples of their mechanical and physical properties. Examples that illustrate the properties of commercially available materials are also provided.

This article focuses on the physical metallurgy and weldability of four families of titanium-base alloys, namely, near-alpha alloy, alpha-beta alloy, near-beta, or metastable-beta alloy, and titanium based intermetallics that include alpha-2, gamma, and orthorhombic systems.

Ultrasound is an ideal modality for nondestructive evaluation (NDE) because it enables the interior of objects to be assessed without the safety and access issues associated with radiography. This article summarizes the history of array usage in NDE and its relationship to medical applications. It discusses the mathematics behind classical beamforming, full matrix capture, and total focusing methods of imaging. The article shows how ultrasonic array data can be simulated by direct numerical methods (most commonly using finite-element methods), analytical methods, or hybrid methods. It also considers various methods of comparing the performance of arrays and imaging algorithms. The article provides a comparison of various advanced and nonlinear imaging algorithm and looks at some practical industrial applications of arrays. It concludes with some future perspectives for arrays in NDE.

This article summarizes the understanding of the mechanisms and mechanical effects of fatigue processes in highly brittle materials, with particular emphasis on ceramics. It provides a discussion on room-temperature fatigue crack growth in monolithic ceramics, transformation-toughened ceramics, and ceramic composites under cyclic compression. The cyclic damage zones ahead of tensile fatigue cracks, crack propagation under cyclic tension or tension-compression loads, and elevated-temperature fatigue crack growth in monotonic and composite ceramics, are discussed. The article presents ceramic fatigue data for fatigue crack growth testing and concludes with a discussion on life prediction for ceramics or ceramic-matrix composites.

This article schematically illustrates a fiber placement system and provides information on the applications of fiber placement. It discusses materials and design considerations for fiber placement. The article provides information on techniques that can be used to eliminate areas of missing tows.

Polymeric floor coatings refer to flooring materials composed of multicomponent thermoset resins formulated with various fillers and pigments that are installed in situ, usually over concrete substrates. Polymeric flooring systems, specified for all industrial and commercial environments, use a variety of polymer chemistries and are constructed in a variety of methods and designs. This article provides a description of the service conditions for the polymeric flooring systems. It provides information on polymeric flooring systems, including thin-film coatings, self-leveling systems, membrane systems, broadcast systems, troweled systems, and terrazzo. The article also focuses on properties, applications, testing, and factors and requirements to be considered during the installation of polymeric floor coatings. It concludes with a discussion about coating failures, including bonding, cracking, chemical attack, and moisture that affect the polymeric floor coatings on concrete.

Brittle materials, such as ceramics, intermetallics, and graphites, are increasingly being used in the fabrication of lightweight components. This article focuses on the design methodologies and characterization of certain material properties. It describes the fundamental concepts and models associated with performing time-independent and time-dependent reliability analyses for brittle materials exhibiting scatter in ultimate strength. The article discusses the two-parameter and three-parameter Weibull distribution for representing the underlying probability density function for tensile strength. It reviews life prediction reliability models used for predicting the life of a component with complex geometry and loading. The article outlines reliability algorithms and presents several applications to illustrate the utilization of these reliability algorithms in structural applications.