Search Results for matrix-toughening methods

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.

This article illustrates the polymer matrices used for composite materials. It describes the use of prepeg materials in manufacturing high-performance composites. The article discusses the various infusion processes for the development of fiber-reinforced composites, namely, resin transfer molding, vacuum-assisted resin transfer molding, and resin film infusion. It explains the composite- and matrix-toughening methods for fiber-reinforced composites, such as dispersed-phase toughening and interlayer toughening. The article concludes with information on optical microscopy, which provides an insight into the micro- and macrostructure of fiber-reinforced composites.

This article describes methods for analyzing impact-damaged composites in the aircraft industry. These include C-scan and x-radiography methods and optical microscopy. The article reviews brittle-matrix composite and tough-matrix composite failures. It explains the different types of composite failure mechanisms such as thermoplastic-matrix composite failure mechanisms, untoughened thermoset-matrix composite failure mechanisms, toughened thermoset-matrix composite failure mechanisms, dispersed-phase and rubber-toughened thermoset-matrix composite failure mechanisms, and particle interlayer-toughened composite failure mechanisms.

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.

The design of structural components with nominally brittle materials is largely determined by their elastic moduli, density, and tensile strength. This article discusses some of the factors involved in the design and reliability through considerations of toughness and ductility of nominally brittle materials. It describes toughening by various bridging mechanisms, as well as process zone effects and their interaction with the bridging rupture zone. The article explains the phenomena that give rise to exceptional toughness and notch-insensitive mechanical behavior. It provides a schematic illustration of a basic cell model to characterize the inelastic strains that occur in ceramic-matrix composites and their dependence on the interface friction.

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.

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.

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.

Microstructural analysis of the composite matrix is necessary to understand the performance of the part and its long-term durability. This article focuses on the microstructural analysis of engineering thermoplastic-matrix composites and the influence of cooling rate and nucleation on the formation of spherulites in high-temperature thermoplastic-matrix carbon-fiber-reinforced composites. It also describes the microstructural analysis of a bio-based thermosetting-matrix natural fiber composite system.

The analysis of composite materials using optical microscopy is a process that can be made easy and efficient with only a few contrast methods and preparation techniques. This article is intended to provide information that will help an investigator select the appropriate microscopy technique for the specific analysis objectives with a given composite material. The article opens with a discussion of macrophotography and microscope alignment, and then goes on to describe various illumination techniques that are useful for specific analysis requirements. These techniques include bright-field illumination, dark-field illumination, polarized-light microscopy, interference and contrast microscopy, and fluorescence microscopy. The article also provides a discussion of sample preparation materials such as dyes, etchants, and stains for the analysis of composite materials using optical microscopy.

This article describes the microcrack analysis of composite materials using bright-field illumination, polarized light, dyes, dark-field illumination, and epi-fluorescence.

This article discusses the properties and uses of structural ceramics and the basic processing steps by which they are made. It describes raw material preparation, forming and fabrication, thermal processing, and finishing. It provides information on the composition, microstructure, and properties of aluminum oxides, aluminum titanate, silicon carbide, boron carbide, zirconia, silicon nitride, silicon-aluminum-oxynitride, and several ceramic composites. It also explains how these materials maintain their mechanical strength and dimensional tolerances at high temperatures and how some of their shortcomings are being addressed.

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 discusses the three basic elements of an epoxy resin formulation that must be understood when selecting a thermoset system. These include base resins, epoxy resin curatives, and modifiers. The article provides examples of epoxy resin formulations that illustrate how raw materials are combined to tailor a formulation to a specific application. It concludes with a discussion on general guidelines for the safe handling of epoxy resins and their associated products.

Cyanate ester resins are a family of high-temperature thermosetting resins that bridge the gap in thermal performance between engineering epoxy and high-temperature polyimides. This article discusses the chemistry, properties and characteristics of the cyanate ester resins. It describes the processing procedures for the cyanate ester resins and provides information on properties for selected applications, such as space applications, radomes, and printed circuit boards.

Ceramics are materials with the potential for a wide range of high-speed finishing operations and for high removal rate machining of difficult-to-machine materials. This article describes the production process, composition, properties, and applications of ceramic tool materials. It presents a comprehensive discussion on the properties and composition of alumina-base tool materials, including alumina and titanium carbide, alumina-zirconia, and silicon carbide whisker reinforced alumina, and silicon nitride base tool materials.

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.

Adhesive bonding is used to assemble composite components into larger structures. Finished components that are damaged during assembly or service are often repaired with adhesive-bonding techniques. This article summarizes criteria for adhesive selection and illustrates typical secondary adhesively bonded joint configurations. It discusses the highly loaded joint considerations of adhesives. The article describes the epoxy adhesives commonly used for the bonding or repair of composite structures. It discusses the surface preparation of composites and metals, and honeycomb processing, including perimeter trimming, mechanical forming, heat forming, core splicing, contouring, and cleaning. The article presents basic steps involved in the adhesive-bonding process and concludes with a discussion on adhesive applications and tooling.

This article provides a summary of the concepts discussed in the articles under the Section “Constituent Materials” in ASM Handbook, Volume 21: Composites. The Section describes the major matrix resins and reinforcing fibers used in composite materials, as well as some of the intermediate material forms available for composite fabrication.