Search Results for double-pass impregnation

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.

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.

Filament winding is a process for fabricating a composite structure in which continuous reinforcements, either previously impregnated with a matrix material or impregnated during winding, is placed over a rotating form or mandrel in a prescribed way to meet certain stress conditions. This article describes the advancements in filament winding and lists the advantages and disadvantages of filament winding. It discusses the effects of fiber tension in filament winding and the selection of fibers, resins, and materials for filament winding. The article emphasizes the three basic filament-winding patterns, such as helical, polar, and hoop. It presents information on the applications of filament winding, including rocket motors, natural gas vehicle (NGV) tanks, and sporting goods. The article presents recommendations for the basic design guidelines for filament-winding design/manufacturing process and concludes with a discussion on fabrication recommendations.

This article provides a discussion on the machining guidelines that serve to improve the machinability of powder metallurgy materials. It provides a description of various cutting tool grades and tool-edge design and describes the machining conditions for common operations, namely, turning, drilling, tapping, grinding, and finishing. The article introduces a few overlooked details that can heavily influence the performance and success of the machining process. These include dwell, margin design on round tools, and proper edge hone.

Vacuum infusion is a resin injection technique derived from resin transfer molding. This article discusses the characteristics of the technique and its applications. It presents the theory and background of the technique and provides an illustration of how parts are made. The article provides information on the equipment and material used for vacuum infusion. It describes the mechanical properties of components and summarizes the influence of production on the properties. The article concludes with a discussion on design guidelines.

Compression molding is the single largest primary manufacturing process used for automotive composite applications. This article provides an overview of the compression molding process. It describes the basic design, materials, and processing equipment of three main groups of composite materials, namely, glass-fiber-mat-reinforced thermoplastics, long-fiber-reinforced thermoplastics, and sheet molding compounds. The article also presents information on the application examples and market volume of compression molding.

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.

Most magnesium alloys can be joined by gas-tungsten arc welding (GTAW) and gas-metal arc welding (GMAW). This article describes relative weldability ratings and provides information on joint design and surface preparation and the use of filler metals and shielding gases suitable to arc welding of magnesium alloys. The article describes the repair welding of castings, with examples. It concludes with a discussion on heat treatment of castings after welding.

Pultrusion is a cost-effective automated process for manufacturing continuous, constant cross-section composite profiles. This article describes the process characteristics and advantages of pultrusion. It provides information on the applications of pultrusion and discusses the processing equipment and tooling, the material composition, and the process control essential for a basic understanding of the pultrusion process.

Abrasive finishing is a method where a large number of multipoint or random cutting edges are coupled with abrasive grains as a bond or matrix material for effective removal of material at smaller chip sizes. This article provides a broad overview of the various categories of abrasive products and materials, abrasive finishing processes, and the mechanisms of delivering the abrasives to the grinding or machining zone. Abrasive finishing processes, such as grinding, honing, superfinishing, microgrinding, polishing, buffing, and lapping, are discussed. The article presents a brief discussion on abrasive jet machining and ultrasonic machining. It concludes with a discussion on the four categories of factors that affect the abrasive finishing or machining: machine tool, work material, wheel selection, and operational.

This article describes some examples of the different welding processes for gray, ductile, and malleable irons. These processes include fusion welding, repair welding, shielded metal arc welding, gas metal arc welding, flux cored arc welding, gas tungsten arc welding, submerged arc welding, oxyfuel welding, and braze welding. The article discusses various special techniques, such as groove-face grooving, studding, joint design modifications, and peening, for improving the strength of a weld or its fitness for service. The article describes other fusion welding methods such as electrical resistance welding and thermite welding. It reviews thermal spraying processes, such as flame spraying, arc spraying, and plasma spraying, of a cast iron.

This article focuses on the design process, materials, and manufacturing techniques for one-off and low-volume production sailing craft. These include racing yachts of typically 10-20 m length for short coastal events, 20-25 m ocean racers, 24 m America's Cup racing craft, multihull racers of 35 m or more, and large luxury cruising craft. The article discusses the tooling, laminating practice, curing, mold removal, and quality control, for manufacturing hulls, decks, masts, and appendages using composites.

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

Bronze and brass alloys are two key classes of materials in copper-base powder metallurgy applications. They are often compacted using mechanical or hydraulic pressing machines. This article provides an overview of the powder pressing process, providing information on the powder properties of bronze and brass and the roles of lubricant and compaction dies in the pressing process. It discusses the structural defects that originate during the compaction process. The article also describes the major factors that influence the sintering response in bronze, prealloyed bronze, brass, and nickel-silver.

This article discusses the requirements for designing repairable composite structures such as a honeycomb sandwich panel construction and integrally stiffened co-cured composite structures. It reviews the general and specific design guidelines for bolted or riveted repairs and adhesively bonded repairs of the composite structures. The article presents several examples to illustrate how these repairs can be achieved.

Mechanical finishes usually can be applied to aluminum using the same equipment used for other metals. This article describes the two types of grinding used in mechanical finishing: abrasive belt grinding and abrasive wheel grinding. It reviews the binders and fluid carriers used in buffing, and discusses satin finishing and barrel finishing. It also describes lapping and honing techniques that are of special interest in treating aluminum parts that have received hard anodic coatings. Honing recommendations for aluminum alloys are presented in a table.

Mechanical cleaning systems are used to remove contaminants of work surface by propelling abrasive materials through any of these three principal methods: airless centrifugal blast blade- or vane-type wheels; compressed air, direct-pressure dry blast nozzle systems; or compressed-air, indirect-suction (induction) wet or dry blast nozzle systems. This article focuses on the abrasive media, equipment, applications, and limitations of dry and wet blast cleaning. It discusses the health and safety precautions to be taken during mechanical cleaning.

This article provides information on the microstructure of powder metal alloys and the special handling requirements of porous materials. It covers selection, sectioning, mounting, grinding, and polishing, and describes procedures, such as washing, liquid removal, and impregnation, meant to preserve pore structures and keep them open for analysis. The article compares and contrasts the microstructures of nearly 50 powder metal alloys, using them to illustrate the effect of consolidation and compaction methods as well as particle size, composition, and shape. It discusses imaging equipment and techniques and provides data on etchants and etching procedures.

This article describes some of the welding discontinuities and flaws characterized by nondestructive examinations. It focuses on nondestructive inspection methods used in the welding industry. The sources of weld discontinuities and defects as they relate to service failures or rejection in new construction inspection are also discussed. The article discusses the types of base metal cracks and metallurgical weld cracking. The article discusses the processes involved in the analysis of in-service weld failures. It briefly reviews the general types of process-related discontinuities of arc welds. Mechanical and environmental failure origins related to other types of welding processes are also described. The article explains the cause and effects of process-related discontinuities including weld porosity, inclusions, incomplete fusion, and incomplete penetration. Different fitness-for-service assessment methodologies for calculating allowable or critical flaw sizes are also discussed.