This article presents the failure of polymer-matrix composites and the methodology for fractography. It provides a detailed discussion on the types of translaminar, interlaminar, and intralaminar failures. The article also presents a discussion on the types of fatigue failures, and the influence of composite architecture. It provides details of the fractography associated with defects and damage.

According to International Organization for Standardization (ISO)/ASTM International 52900, additive manufacturing (AM) can be classified into material extrusion, material jetting, vat photo polymerization, binder jetting, sheet lamination, powder-bed fusion (PBF), and directed-energy deposition. This article discusses the processes involved in polymer powder 3D printing using laser fusion/ sintering and fusing agents and energy, as well as the thermally fused PBF. It provides information on polymer powder parameters and modeling, the powder-handling system, powder characterization, the flowability of powder feedstock, and polymer part characteristics. The article describes the types of polymers in PBF, the processes involved in powder recycling, and the prospects of PBF in AM. In addition, the biomedical application of polyether ether ketone (PEEK) is also covered.

This article briefly introduces some commonly used methods for mechanical testing. It describes the test methods and provides comparative data for the mechanical property tests. In addition, creep testing and dynamic mechanical analyses of viscoelastic plastics are also briefly described. The article discusses the processes involved in the short-term and long-term tensile testing of plastics. Information on the strength/modulus and deflection tests, impact toughness, hardness testing, and fatigue testing of plastics is also provided. The article describes tension testing of elastomers and fibers. It covers two basic methods to test the mechanical properties of fibers, namely the single-filament tension test and the tensile test of a yarn or a group of fibers.

Engineering plastics, as a general class of materials, are prone to the development of internal stresses which arise during processing or during servicing when parts are exposed to environments that impose deformation and/or temperature extremes. Thermal stresses are largely a consequence of high coefficients of thermal expansion and low thermal diffusivities. Although time-consuming techniques can be used to analyze thermal stresses, several useful qualitative tests are described in this article. The classification of internal stresses in plastic parts is covered. The article describes the effects of low thermal diffusivity and high thermal expansion properties, and the variation of mechanical properties with temperature. It discusses the combined effects of thermal stresses and orientation that result from processing conditions. The article also describes the effect of aging on properties of plastics. It explains the use of high-modulus graphite fibers in amorphous polymers.

This article provides an overview of the physics and math associated with moisture-related failures in plastic components. It develops key equations, showing how they are used to analyze the causes and effects of water uptake, diffusion, and moisture concentration in polymeric materials and resins. It explains how absorbed moisture affects a wide range of properties, including glass transition temperature, flexural and shear modulus,creep, stress relaxation, swelling, tensile and yield strength, and fatigue cracking. It provides relevant data on common polymers, resins, and fiber-resin composites.

This article focuses on manufacturing-related failures of injection-molded plastic parts, although the concepts apply to all plastic manufacturing processes It provides detailed examples of failures due to improper material handling, drying, mixing of additives, and molecular packing and orientation. It also presents examples of failures stemming from material degradation improper use of metal inserts, weak weld lines, insufficient curing of thermosets, and inadequate mixing and impregnation in the case of thermoset composites.

Reinforced polymers (RPs) are widely used in structural, industrial, automotive, and engineering applications due to their ecofriendly nature and the potential to manipulate their properties. This article addresses the technical synthesis of RPs, referring to their tribological behavior, to provide insights into the contribution and interaction of influential parameters on the wear behavior of polymers. It provides a brief discussion on the effects of significant parameters on RP tribology. The article describes abrasive and adhesive wear and provides a theoretical synthesis of the literature regarding the wear mechanisms of RPs. It also describes the synthesis of abrasive wear failure of different types of RPs and highlights the contribution of these influential parameters. The article addresses the synthesis of adhesive wear failure of different types of RPs.

Tungsten, molybdenum, and cemented carbide parts can be produced using several additive manufacturing technologies. This article classifies the most relevant technologies into two groups based on the raw materials used: powder-bed methods, such as selective laser melting, electron beam melting, and binder jet three-dimensional (3-D) printing, and feedstock methods, such as fused-filament fabrication and thermoplastic 3-D printing. It discusses the characteristics, processing steps, properties, advantages, limitations, and applications of these technologies.

Aluminum alloys are widely used in engineered components because of their excellent strength-to-weight ratio. Their use in applications requiring wear resistance is more limited. One of the main limitations of aluminum alloys is the poor tribological behavior mainly due to their relatively low hardness, which favors large plastic deformation under sliding conditions. This article discusses the classes and mechanisms of wear in aluminum-silicon alloys, aluminum-tin bearing alloys, and aluminum-matrix composites; describes the effect of material-related parameters on wear behavior of these alloys; and reviews their applications in a variety of tribological applications in the automotive industry ranging from aluminum-tin alloys for plain bearings to alloys with hard anodizing for machine elements. Methods to improve wear resistance and alloy hardness are also discussed.

In general, metal-matrix composites (MMCs) are classified into three broad categories: continuous fiber-reinforced composites, discontinuous or short fiber-reinforced composites, and particle-reinforced composites. This article focuses on stir casting and melt infiltration as the two main methods of MMC solidification processing. It describes the MCC casting methods, such as sand and permanent mold casting, centrifugal casting, compocasting, and high-pressure die casting. The article discusses the MMC infiltration processes in terms of pressure infiltration casting and liquid metal infiltration. It reviews the powder metallurgy processing of aluminum MMCs and deformation processing of discontinuously reinforced aluminum composites. The article concludes with a discussion on the processing of fiber-reinforced aluminum.

The horsepower requirements to cut various metal alloys provide an indication of the relative ease and cost of machining, but several other important factors include cutting tool material, chip formation, cutting fluids, cutting tool wear, surface roughness, and surface integrity. This article reviews these general machining factors as well as specific cutting tool and cutting parameters for the six basic chip-forming processes of turning, shaping, milling, drilling, sawing, and broaching. Best practices for each of the six chip-forming processes are suggested for optimized machining of aluminum alloys. The article lists the inherent disadvantages of machining processes that involve compression/shear chip formation. It discusses the machining of aluminum metal-matrix composites and nontraditional machining of aluminum, such as abrasive jet, waterjet, electrodischarge, plasma arc, electrochemical, and chemical machining.

Aluminum powders can be formed into components by several competing technologies, including powder metallurgy (PM), metal injection molding, powder forging, and additive manufacturing. This article explores PM methodologies that are being exploited to manufacture such components. It reviews emerging technologies that promise to offer exciting ways to produce aluminum parts. The article discusses the various steps involved in PM, such as powder production, compaction, sintering, repressing, and heat treatment. It provides information on aluminum production statistics and the wear-resistance applications of PM.

Weldability is a function of three major factors: base material quality, welding process, and design. This article focuses on base-metal weldability of aluminum alloys in terms of mechanical property degradation in both the weld region and heat-affected zone, weld porosity, and susceptibility to solidification cracking and liquation cracking. It provides an overview on welding processes, including gas metal arc welding, gas tungsten arc welding, resistance spot and seam welding, laser beam welding, and various solid-state welding processes. A review on joint design is also included, mainly in the general factors associated with service weldability (fitness). The article also provides a discussion on the selection and weldability of non-heat-treatable aluminum alloys, heat treatable aluminum alloys, aluminum-lithium alloys, and aluminum metal-matrix composites.

This article describes the direct hot extrusion process and the typical sequence of operations for producing extruded aluminum shapes from soft and medium-grade aluminum alloys, hard alloys, and aluminum-matrix composites. It discusses key process variables, including extrusion speed and exit temperature, and their effect on product quality. The article also provides information on extrusion presses, press dies, and tooling, and addresses quality issues such as surface defects, blistering, and internal cracking. It concludes with a discussion on the drawing of solid section and aluminum tube.

Electromagnetic signals at microwave and millimeter-wave frequencies are well suited for inspecting dielectric materials and composite structures in many critical applications. This article presents a partial list of reported nondestructive testing (NDT) application areas for microwaves. It discusses the advantages and limitations of inspection with microwaves. The article discusses the physical principles, including reflection and refraction, absorption and dispersion, scattering, and standing waves. It provides a discussion on terahertz (THz) imaging for nondestructive evaluation (NDE). The article concludes with information on ground-penetration radar (GPR) that uses electromagnetic radiation and detects the reflected signals from subsurface structures.

Acoustic emission is the generation of stress waves by sudden movement in stressed materials. This article begins with a comparison of acoustic emission from most other nondestructive testing (NDT) methods, and discusses the range of applicability of acoustic emission. It describes the instrumentation principles of acoustic emission and reviews the role of acoustic emission in materials studies. The article illustrates the testing of metal-matrix composites (MMCs) using acoustic emission and the use of acoustic emission inspection in production quality control. It concludes with information on the structural test applications of acoustic emission inspection to find defects and to assess or ensure structural integrity.

This article discusses the fundamentals and operating principles of the following acoustic microscopy methods: scanning laser acoustic microscopy, C-mode scanning acoustic microscopy, and scanning acoustic microscopy. It describes the applications of acoustic microscopy for detecting defects in metals, ceramics, glasses, polymers, and composites with examples.

This article introduces the principal methodologies and some advanced technologies that are being applied for nondestructive evaluation (NDE) of fiber-reinforced polymer-matrix composites. These include acoustic emission, ultrasonic, eddy-current, computed tomography, electromagnetic acoustic transducer, radiography, thermography, and low-frequency vibration methods. The article also provides information on NDE methods commonly used for metal-matrix composites.