Search Results for composites

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.

This article discusses the formation of braided structures on a standard maypole-style braiding machine and reviews three-dimensional braiding and radial braiding machines. It illustrates several examples of braided structures with unique tow compositions and discusses properties of braided structures and test methods. The article provides a case study of braid-reinforced composites and a second case study in which a triaxial braided sleeving was taken up onto a contoured drum following the formation of the braided structure.

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.

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.

This article discusses the importance of friction and wear and the role of lubricants in composites. It highlights the progress and developments in using different forms of carbon allotropes in composites for improved friction and wear performance of materials. The article focuses on the widely used form known as carbon black (CB) and shows how to deal with friction and wear of polymers and composites when gamma irradiation is involved. It also discusses the role of graphite in composite materials, which is widely used as a dry lubricant. The article examines the tribology of carbon nanotubes (CNTs) as components in composite materials. It also highlights some of the most pronounced examples of graphene use as a reinforcement agent for improving tribological performance in composite matrices. The article concludes with a discussion on the progress of research in diamond-containing composites.

Polymers and polymer composites have become attractive for tribological applications due to their specific material properties. This article begins by discussing the fundamentals of polymer friction and wear. It summarizes the main polymer materials used in tribological applications. The article explains the effects of load, sliding velocity, and temperature on the friction coefficient. It describes three types of wear modes, namely, abrasive, adhesion, and fatigue. The article discusses the frictional behavior of polymer composites and polymer coatings. It concludes by providing information on tribotesting of polymers and polymer composites.

This article begins by describing the designations of cast and wrought aluminum alloys. It explains the effects of main alloying elements in aluminum alloys: boron, chromium, copper, iron, lithium, magnesium, manganese, nickel, phosphorus, silicon, sodium, strontium, titanium, and zinc. The article describes the microstructure of cast and wrought aluminum alloys and the various strengthening mechanisms, including solid solution, grain refinement, strain or work hardening, precipitation (or age) hardening, and dispersoid strengthening. The article explicates the tribological behavior of aluminum alloys, aluminum-base composites, and metal-matrix composites. It presents the effect of material-related parameters and external factors on wear behavior and transitions of aluminum-silicon alloys. The article also presents the most important factors affecting the dry sliding wear behavior of particle-reinforced aluminum-base composites against a steel counterface.

Magnesium-matrix composites (MgMCs) are very promising as structural materials because of their low density, high specific strength, and excellent castability. This article provides information on the characteristics, mechanical properties, and applications of magnesium alloys and composites. It discusses the microstructures used for the most common magnesium alloys used in metal-matrix composites, namely, magnesium-aluminum, magnesium-rare earth and magnesium-lithium alloys. The article focuses on the most common methods of heat treatment, including solution heat treatment, precipitation strengthening or aging, and annealing, applied to these alloys. Finally, it describes the microstructural aspects and precipitate-matrix relationships of MgMCs as well as the heat treatment methods for MgMCs.

Metal matrix composites (MMCs) can be synthesized by vapor phase, liquid phase, or solid phase processes. This article emphasizes the liquid phase processing where solid reinforcements are incorporated in the molten metal or alloy melt that is allowed to solidify to form a composite. It illustrates the three broad categories of MMCs depending on the aspect ratio of the reinforcing phase. The categories include continuous fiber-reinforced composites, discontinuous or short fiber-reinforced composites, and particle-reinforced composites. The article discusses the two main classes of solidification processing of composites, namely, stir casting and melt infiltration. It describes the effects of reinforcement present in the liquid alloy on solidification. The article examines the automotive, space, and electronic packaging applications of MMCs. It concludes with information on the development of select cast MMCs.

This article discusses the solidification of a matrix alloy in cast metal matrix composites (MMCs). It begins with a discussion on the mixing techniques in reinforcement incorporation and wettability of reinforcement. It describes the solidification processes, such as stir mixing and melt infiltration, used in the synthesis of MMCs. The article also considers the fundamentals of the process and presents a computational modeling of particle/solidification front interactions in metal-ceramic systems. The article concludes with information on nanocomposites.

Discontinuously reinforced aluminum (DRA) alloy metal-matrix composites (MMCs) represent an advanced aluminum materials concept whereby ceramic particles, or whiskers, are added to aluminum-base alloys through the use of either ingot-melting or casting and/or powder-metallurgy (P/M) techniques. This article begins with a summary of general observations on the forging of discontinuously reinforced composites. It provides information on some of the specific experimental results obtained on various DRA systems, including 2xxx DRA alloys and cast DRA alloys. The article reviews the efforts on the modeling of behavior of specific alloy systems, with a comparison of experimental results to the modeling attempts. It concludes with information on the properties of deformation-processed DRA alloys.

This article describes the four major conditions that can cause beryllium to corrode in air. These include beryllium carbide particles exposed at the surface; surface contaminated with halide, sulfate, or nitrate ions; surface contaminated with other electrolyte fluids; and atmosphere that contains halide, sulfate, or nitrate ions. The article provides information on the behavior of beryllium under the combined effects of high-purity water environment, stress and chemical environment, and high-temperature environment. The compositions of the structural grades for intentionally controlled elements and major impurities are tabulated. The article discusses the in-process problems and procedures that are common but avoidable when processing beryllium and aluminum-beryllium composites. It also describes the types of coatings used on beryllium and aluminum-beryllium. These include chemical conversion coatings, anodized coatings, plated coatings, organic coatings, and plasma-sprayed coatings.

This article describes the resin and fabrication requirements associated with fiberglass-reinforced plastic equipment. It provides a discussion on various resins and their resistance to various environments. These include polyester, epoxy, epoxy vinyl-ester, and furan and phenolic thermosetting resins. The article concludes with a discussion on the curing system of thermosetting resins.

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 describes how composite specimens are sectioned, documented, and labeled during sample preparation. The mounting procedures for the specimen are summarized. The article explains sample clamping, which involves not mounting the specimens using an adhesive or casting resin and corresponds to clamped samples used in automated polishing heads. It details that cavity molds involve mounting the composite specimens using a casting resin in a preset mold. The article also discusses the mounting of composite materials for hand polishing.

This article focuses on the sample preparation methods for titanium honeycomb composites, boron fiber composites, and titanium/polymeric composite hybrids. These include mounting, sectioning, grinding, and polishing. The article also provides information on the sample preparation of unstaged and staged prepreg materials for optical analysis.

This article describes the various aspects relating to the selection and preparation of ultrathin-section specimens of fiber-reinforced polymeric composites for examination by transmitted light microscopy. It provides information on the contrast-enhancement methods used by transmitted-light microscopy and optimization of microscope conditions. Examples of composite ultrathin sections analyzed using transmitted-light microscopy contrast methods are also presented.

This article describes the dispersed-phase toughening of thermoset matrices by the development of multiphase-structure thermosetting matrices using rubber and/or thermoplastic materials. It discusses two main methods for manufacturing prepregs, namely, single-pass impregnation and double-pass impregnation. The article illustrates reflected-light optical microscopy techniques to evaluate the morphology of thermoplastic materials for determining the material quality and correlating key microstructural features with material performance.