Search Results for matrix precursor impregnants

This article describes the manufacture, post-processing, fabrication, and properties of carbon-carbon composites (CCCs). Manufacturing techniques with respect to the processibility of different geometries of two-directional and multiaxial carbon fibers are listed in a table. The article discusses matrix precursor impregnants, liquid impregnation, and chemical vapor infiltration (CVI) for densification of CCCs. It presents various coating approaches for protecting CCCs, including pack cementation, chemical vapor deposition, and slurry coating. Practical limitations of coatings are also discussed. The article concludes with information on the mechanical properties of CCCs.

Ceramic-matrix composites (CMCs) have ability to withstand high temperatures and have superior damage tolerance over monolithic ceramics. This article describes important processing techniques for CMCs: cold pressing, sintering, hot pressing, reaction-bonding, directed oxidation, in situ chemical reaction techniques, sol-gel techniques, pyrolysis, polymer infiltration, self-propagating high-temperature synthesis, and electrophoretic deposition. The advantages and disadvantages of each technique are highlighted to provide a comprehensive understanding of the achievements and challenges that remain in this area.

This article describes the various pure forms of carbon matrices and the corresponding methods used to create them or incorporate them into a matrix of a composite. These forms include graphite, diamond, fullerenes, and nanotubes. The article discusses the three types of liquid precursors, namely, thermoplastic, thermosetting, and evaporative or solvent carriers. It provides a description of the advantages and limitations of various methods involved in chemical vapor infiltration. The article concludes with a discussion on matrix contribution to composite properties.

Carbon-carbon composites (CCCs) are introduced in fields that require their high specific strength and stiffness, in combination with their thermoshock resistance, chemical resistance, and fracture toughness, especially at high temperatures. The use of CCCs has expanded as the price of carbon fibers has dropped and their mechanical properties have increased. This article begins with an overview of the carbon conversion processes, fiber properties and microstructures, and interfacial bonding and environmental interaction of carbon fibers, followed by a detailed discussion on the various techniques available for processing CCCs for specific applications, including preform fabrication (fiber weaving), densification, application of protective coatings, and joining. The article closes with a description of the mechanical and physical properties and applications of CCCs. The main applications of CCCs, in terms of money and mass, are in the military, space, and aircraft industries.

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.

This article describes the most significant tests to characterize the properties of constituent materials. It discusses the chemical, physical, and mechanical tests for determining the properties of reinforcement fibers and fabrics. The article provides information on some of the basic materials used for thermoset and thermoplastic resin matrices. It reviews the identification of the individual characteristics of thermoset and thermoplastic resin along with the test methods normally used for their determination. The article contains a table that lists properties and tests for uncured and cured thermoset-matrix resins and prepregs.

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 discusses the types, properties, and uses of continuous-fiber-reinforced composites, including glass, carbon, aramid, boron, continuous silicon carbide, and aluminum oxide fiber composites. While polyester and vinyl ester resins are the most used matrix materials for commercial applications, epoxy resins, bismaleimide resins, polyimide resins, and thermoplastic resins are used for aerospace applications. The article addresses design considerations as well as product forms and fabrication processes.

This article addresses the types, properties, forms, and applications of fibers that are available for use in fiber-reinforced polymeric matrix composites, including glass, graphite, carbon, aramid, boron, silicon carbide, ceramic, continuous oxide and discontinuous oxide fibers. It describes the functions, types, and chemical composition of fiber sizing agents. The article discusses the styles, properties, applications, and weaving methods of unidirectional, two-directional and multidirectionally reinforced fabrics. The article also reviews the use of prepreg resins in aerospace and lower performance applications.

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.

This article presents a comprehensive collection of the definition of terms related to metallurgy.

Carbon-carbon is a unique composite material in which a nonstructural carbonaceous matrix is reinforced by carbon fibers to create a heat-resistant structural material that finds application in the aerospace and defense industries. This article provides a detailed account of the fundamentals of protecting carbon-carbon composites and explains the various coating deposition techniques, namely, pack cementation, chemical vapor deposition, and slurry coatings. It includes information on the practical limitations of coatings for the carbon-carbon composites.

This article begins with a brief history of composite materials and discusses its characteristics. It presents an introduction to the constituents, product forms, and fabrication processes of composite materials. The article concludes with a discussion on the applications of organic-matrix, metal-matrix, and ceramic-matrix composites.

This article discusses the properties and applications of two types of polyimide resins: condensation polyimides and addition-type polyimides. It describes the chemistry of condensation-type polyimides during synthesis, processing of polyamide acid precursor solution to polyimide, and preparation of polyimide films from thermoplastic polyamic acid precursors. The article reviews the chemistry of several addition-type polyimides, including phenylethynyl-containing imide oligomers, nadic end-capped polyimides, and LARC RP46. It explains the preparation processes of nadic end-capped amic acid oligomer resin solutions, including the preparation of resin powder and resin disks, adhesive film, adhesive bond specimens, and films.

Post-processing includes various processes that might be required to produce finished components from the ceramic-matrix composites (CMC) materials. The processes consist of machining or finishing operations, coating, joining, assembly operations, and nondestructive evaluation of CMCs and its components. This article discusses the specific needs for science and technology in these areas relative to the goal of employing CMCs in a variety of applications.

This article is intended to assist the development of procedures for the brazing of ceramic-to-ceramic or ceramic-to-metal joints for service under elevated temperatures, mechanical or thermal stresses, or corrosive atmospheres. It describes the factors considered in preparing a procedure for the brazing of graphitic materials.

Fiber-matrix adhesion is a variable to be optimized in order to get the best properties and performance in composite materials. This article schematically illustrates fiber matrix interphase for composite materials. It discusses thermodynamics of interphase in terms of surface energy, contact angle, work of adhesion, solid surface energy, and wetting and wicking. The article describes the change in interphase depending on the reinforcing fiber such as glass fiber, polymeric fiber, and carbon fiber. It emphasizes fiber-matrix adhesion measurements by direct methods, indirect methods, and composite laminate tests. The effects of interphase and fiber-matrix adhesion on composite mechanical properties, such as composite on-axis properties, composite off-axis properties, and composite fracture properties, are also discussed.

This article begins with a discussion on fiber-reinforced composite materials and describes the generic behavior and structure/property relationships of composites. The article summarizes lamina properties and presents equations that help in the calculation of lamina properties. Composite laminates are constructed from lamina with uniaxial fiber orientation and frequently from textile fabrics as well. The article explains the characteristics of symmetric in-plane and through-thickness laminates; asymmetric in-plane and symmetric through-thickness laminates; asymmetric laminates; and curved laminates. It provides information on controlled thermal expansion composites, metal-matrix composites, and ceramic-matrix composites. The article illustrates the types of bonded joints and concludes with a discussion on design for manufacturing.