The primary motivation for the insertion of metal-matrix composites (MMCs) into aeronautical systems is the excellent balance of specific strength and stiffness offered by MMCs. This article provides information on the aerostructural, aeropropulsion, and aeronautical subsystem applications of MMCs. The applications include ventral fin, fuel access door covers, helicopter blade sleeve, fan exit guide vane, nozzle actuator piston rod, nozzle actuator links, T-1 racks, and hydraulic manifold.

This article discusses composites for unmanned space vehicles and provides an overview of key design drivers, challenges, and environment for use of composites in spacecraft, launch vehicles, and missiles. It describes the design allowable properties of composite materials. The article provides information on the specific state-of-the-art applications of composite materials for spacecraft missiles and launch vehicles. A discussion on the key applications, including solid rocket motor casings, payload fairings, and payload support structures, is presented.

The inclusion of damage tolerance design and a systematic review of design procedures allow the U.S. Air Force to design, manufacture, and maintain systems that are structurally safe and economically prudent. After a brief introduction of fracture mechanics, this article describes the particular aspects that relate to damage tolerance in aircraft design. It discusses the use of fracture mechanics as a method of predicting failure, understanding failure mechanisms, and suggesting inspection methods to protect against failure in pressure vessels. Various programs of U.S. Air Force to design aircraft structure, namely, airframe structural integrity programs, engine structural integrity program, and mechanical subsystems structural integrity program are also discussed.

Autoclave molding is a process used to impart a controlled heat and pressure cycle cure to a layup. This article describes the materials used for preparing a layup, including peel ply, separator, bleeder, barrier, breather, dam, and vacuum bag. It describes the major elements and functions of an autoclave system, including pressure vessel, gas stream heating and circulation sources, gas stream pressurizing systems, vacuum systems, control systems, and loading systems. The article includes information about modified autoclaves for specialized applications and safety practices in autoclave molding. It also describes the tooling configuration and type of tooling which includes aluminum and steel tooling, electroformed nickel tooling, graphite-epoxy tooling, and elastomeric tooling.

This article introduces the concept of condition monitoring (CM) and summarizes various techniques used for CM across the industrial sectors. The techniques include visual inspection, performance monitoring, vibration condition monitoring, vibration condition monitoring, lubricant oil analysis, acoustic emission testing, temperature monitoring, motor current signature analysis, and ultrasound emission. The article describes the evolution of condition-based maintenance in CM. It also describes the basics of integrated vehicle health management, a capability that enables a number of maintenance philosophies. The article concludes with a discussion on various condition monitoring in industrial sectors, including condition-monitoring techniques in nuclear power plants, road condition monitoring, and condition monitoring in wind turbines.

This article presents the use of additive manufacturing (AM) in the space industry. It discusses metal AM processes and summarizes metal AM materials, including their relevant process categories and references. It also presents the design for AM for spacecraft. The article also provides an overview of in-space manufacturing and on-orbit servicing, assembly, and manufacturing. It presents some of the specific areas that must be understood for the qualification of AM. The article also discusses future trends, challenges, and opportunities for aerospace.

Reliability is a measure of the capacity of equipment or systems to operate without failure in the service environment. This article focuses on reliability in design and presents equations governing the instantaneous failure rate, general reliability function, mean time to failure, mean time between failures, and useful life period. The article describes the calculation of reliabilities for series and parallel arrangements of a complex system. It provides a comparison of probabilistic and deterministic design and concludes with a discussion on reliability growth.

This article reviews business cases for additive manufacturing (AM) and offers suggestions on monetizing the flexibility created by AM through a deep understanding of the most applicable cost drivers. It also reviews the common adoption drivers for AM and provides suggestions on how to take advantage of them. The AM maturity model breaks down potential additively manufactured products into five levels: preproduction, production influence, substitution, functional designs, and multifunctional. The business value of these levels is further described and evaluated with respect to the triple constraint of project management. The article then focuses on success factors for implementing AM.

This article reviews corrosion problems in the U.S. Department of Defense (DoD) and discusses management and maintenance aspects of the practices that address the cost and readiness. It describes the plans to institute corrosion prevention and control strategies under DoD directives in engineering design, material selection, and fabrication processes for new acquisitions. The article also suggests a long-term strategy to reduce the cost of corrosion control.

This article describes the classification of fuel cells depending on the operating temperature and type of electrolytes used. This classification includes alkaline fuel cells, phosphoric acid fuel cells, polymer electrolyte membrane fuel cells (PEMFCs), molten carbonate fuel cells (MCFCs), and solid oxide fuel cells (SOFCs). The article explains the corrosion processes in fuel cells due to solid-gas interactions, solid-liquid interactions, and solid-solid interactions. It discusses the long-term performance stability and long-term degradation processes of PEMFCs, MCFCs, and SOFCs. The article reviews the development of chemically and structurally compatible component materials in PEMFCs, MCFCs, and SOFCs.

This article describes design factors for products used in engineering applications. The article groups these factors into three categories: functional requirements, analysis of total life cycle, and other major factors. These categories intersect and overlap, constituting a major challenge in engineering design. Performance specifications, risk and hazard analysis, design process, design for manufacture and assembly, design for quality, reliability in design, and redesign are considered for functional requirements. Life-cycle analysis considers raw-material extraction from the earth and product manufacture, use, recycling (including design for recycling), and disposal. The other major factors considered include evaluation of the current state of the art for a given design, designing to codes and standards, and human factors/ergonomics.

Reliability-centered maintenance (RCM) is a systematic methodology for preventing failures. This article begins by discussing the history of RCM and uses Society of Automotive Engineers (SAE) all-industry standard JA1011 as its model to describe the key characteristics of an RCM process. It then expands on questions involved in RCM process, offering definitions when necessary. Next, the article describes the approach of RCM to failure modes and effects analysis (FMEA), the failure management policies available under RCM, and the criteria of RCM for deciding when a specific failure management policy is technically feasible. Then, after discussing the ways that RCM classifies failure effects in terms of consequences, it describes how RCM uses failure consequences to identify the best failure management policy for each failure mode. Next, the building blocks of RCM are put together to create a failure management program. The article ends with a discussion on some practical issues pertaining to RCM that lie outside the scope of SAE JA1011.

This article is dedicated to the fields of mechanical engineering and machine design. It also intends to give a nonexhaustive view of the preventive side of the failure analysis of rolling-element bearings (REBs) and of some of the developments in terms of materials and surface engineering. The article presents the nomenclature, numbering systems, and worldwide market of REBs as well as provides description of REBs as high-tech machine components. It discusses heat treatments, performance, and properties of bearing materials. The processes involved in the examination of failed bearings are also explained. Finally, the article discusses in detail the characteristics and prevention of the various types of failures of REBs: wear, fretting, corrosion, plastic flow, rolling-contact fatigue, and damage. The article includes an Appendix, which lists REB-related abbreviations, association websites, and ISO standards.