Sheet molding compounds (SMCs) refers to both material and process for producing glass-fiber-reinforced polyester resin items. This article discusses the material components incorporated into the resin paste for desirable processing and molding characteristics and optimum physical and mechanical properties, including catalyst, fillers, thickeners, pigments, thermoplastic polymers, flame retardants, and ultraviolet absorbers. It talks about the mixing techniques available for SMC resin pastes, including batch, batch/continuous, and continuous mixing. The article also outlines the design features and the operations of continuous-belt and beltless machine type SMCs.

Molding compounds are plastic materials in varying stages of pellets or granulation that consist of resin, filler, pigments, reinforcement, plasticizers, and other ingredients ready for use in a molding operation. This article describes the material components and physical properties of sheet molding compounds (SMC). The three types of resin paste mixing techniques, such as batch, batch/continuous, and continuous, for an SMC operation are reviewed. The article discusses the design features and functional operations of the two types of SMC machines, namely, continuous-belt and beltless machines. It explains the formulation and processing of bulk molding compounds and reviews molding methods for bulk molding compounds, including compression, transfer, and injection molding. The effects of the fiber type and length and the matrix type on thermoset bulk molding compounds are discussed. It describes the four injection molding processes of injection molding compounds such as feeding, transporting, injecting, and flowing.

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.

This article is an informative primer on sealants and the role they play in engineered assemblies. It discusses the physical, thermal, chemical, and electrical properties of sealant materials and the various forms in which they are applied, including liquids, pastes, and extruded tapes. It also describes classifications and types, comparing and contrasting sealants made from oil-based caulks, asphalts, coal tar resins, latex acrylic sealants, polyvinyl acetate caulks, solvent acrylics, butyl sealants, polysulfides, polyurethanes, modified silicones, anaerobics, vinyl plastisols, and polypropylenes. In addition, the article provides practical design insight, addressing application requirements, seal configurations, and joint stresses. It concludes with a brief discussion on the use of sealants in aerospace, automotive, electrical, and construction applications.

The compression molding process is most commonly called the sheet molding compound (SMC) process in reference to the precursor sheet molding compound material it uses. This article discusses the types of materials used for sheet manufacture, and describes the manufacturing and processing parameters of SMC components, providing details on tooling and process advantages and limitations. The article provides a general overview of the types of compression molding processes, including structural compression molding and thermoplastic compression molding.

This article provides an overview of the environmental performance of the most commonly used nonmetallic materials, including elastomers, plastics, thermosetting resins, resin-matrix composites, organic coatings, concrete, refractories, and ceramics. It also discusses the applications and uses of these materials.

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.

Cores are separate shapes of sand that are placed in the mold to provide castings with contours, cavities, and passages that are not otherwise practical or physically obtainable by the mold. This article describes the basic principles of coremaking and the types of core sands, binders, and additives used in coremaking. It discusses the curing of compacted cores by core baking and the hot box processes. The article provides an overview of the core coatings, assembling and core setting, coring of tortuous passages, and cores in permanent mold castings and investment castings. It also discusses the design considerations in coremaking to eliminate cores and compares coring with drilling.

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.

Metal powders are used as fuels in solid propellants, fillers in various materials, such as polymers or other binder systems, and for material substitution. They are also used in food enrichment, environmental remediation market, and magnetic, electrical, and medical application areas. This article reviews some of the diverse and emerging applications of ferrous and nonferrous powders. It also discusses the functions of copier powders and the processes used frequently for copier powder coating.

This article describes the chemistry of phenolic resins and reviews their characteristics and properties for various composites fabrication processes. The fabrication processes include solution/hot-melt process, pultrusion, vacuum infusion, filament winding, sheet molding, and hand lay-up. The article illustrates the manufacturing process of phenolic honeycomb and provides information on the applications of phenolic composites.

This article reviews friction and wear of various dental materials that have been studied by fundamental wear measurements, simulated service wear measurements, and clinical measurements. The materials include dental amalgam, composite restorative materials, pit and fissure sealants, dental cements, porcelain and plastic denture teeth, dental feldspathic porcelain and ceramics, endodontic instruments, periodontal instruments, and orthodontic wires. The article describes the correlations of properties such as the hardness, fracture toughness, and wear. It provides information on wear mechanism such as the sliding adhesive wear, two-body abrasion, three-body abrasion, erosion, and fatigue.

Powder metallurgy (PM) stainless steels, as with conventional PM steels, are often used in the as-sintered condition. In addition to cost considerations, minimization of postsinter handling and secondary operations is also preferred because it reduces the potential for contamination of the parts with particulates and residues, which can result in the appearance of surface rust. This article provides information on various secondary operations, including tumbling, re-pressing, resin impregnation, annealing or heat treating, brazing, machining, and welding. It describes those aspects relating to welding of PM stainless steels, specifically, the effects of density, residual porosity, and sintered chemistry on weldability. Further, the article investigates the influence the sintering atmosphere has on machinability, as well as differences created by the presence of residual porosity.

This article provides a discussion on the metallographic techniques used for failure analysis, and on fracture examination in materials, with illustrations. It discusses various metallographic specimen preparation techniques, namely, sectioning, mounting, grinding, polishing, and electrolytic polishing. The article also describes the microstructure examination of various materials, with emphasis on failure analysis, and concludes with information on the examination of replicas with light microscopy.

Additives for plastics and elastomers are used to increase the ease of processing and to improve the properties of the final product. Additives improve processing characteristics by increasing lubricity and by stabilizing the polymer. Additives that improve properties include those that decrease static charge development and microbial activity and those that improve flame retardation characteristics, color, light stability, impact resistance, density and mechanical properties. This article focuses on the additives for polymers and elastomers that are used for improving processing--blowing agents, mold-release agents, lubricants, plasticizers, and heat stabilizers--and for improving properties antimicrobials, antioxidants, antistatic agents, colorants, fillers and fiber reinforcements, flame retardants, impact modifiers, light stabilizers, plasticizers, and heat stabilizers. Furthermore, it discusses the method for addition of these additives and the problems faced during compounding.

This article focuses on various thermal analysis techniques used to verify the cure of a polymer composite. The techniques include differential scanning calorimetry (DSC), modulated DSC, thermomechanical analysis, dynamic mechanical analysis, and dielectric analysis. The article also provides an overview of the composite failure modes affected by matrix resin and testing approach.

Automated tape laying is a mature process used in both commercial and military aircraft applications. This article provides a brief history of the process and describes the use of commercially available flat and contour tape-laying equipment. It discusses the advantages and disadvantages of the tape laying. The article describes the various components of a ten-axis gantry-type tape laying machine and the tape laying process. It provides a discussion on typical material types and forms for tape laying and provides information on design guidelines for tape laying.

Adhesive bonding is a proven technology in the manufacture of automotive assemblies, helping carmakers achieve weight reduction goals without compromising body stiffness, crash performance, and noise-vibration-handling characteristics. This article discusses the advantages and limitations of adhesive-bonded aluminum joints and the procedures used to produce them. It addresses surface preparation, the addition of interfacial coatings and primers, and the application of thermoplastic and thermosetting resins. The article examines the nature and role of the various layers that constitute the joint and explains how each contributes to performance. It also discusses adhesive selection factors, joint design, and testing procedures.

Filament winding is a process that allows the precise lay-down of continuous reinforcement in predescribed patterns at a high rate of speed. This article discusses the filament winding process and includes a comparison to other compacting and curing processes. The article describes design factors, and techniques to produce aerodynamic surfaces, improve surface smoothness, and avoid slipping and bridging of filament. The article discusses tooling and the equipment used in the filament winding process, namely, mandrel design, winding machines, tensioners, and ovens.

This article begins with an overview of the fundamentals of adhesive technology, including functions, limitations, adhesive joint types, and the key factors in the selection of adhesives, including application, type of joint, process limitation, mechanical requirement, and service conditions. It then focuses on the characteristics, types, and properties of the five groups of adhesives, such as structural, hot melt, pressure sensitive, water based, ultraviolet, and electron beam cured adhesives. The article also discusses the functions and applications of adhesive modifiers, including fillers, adhesion promoters, tackifiers, and tougheners. It gives a short note on functions of primers and primerless bonding. Applications of adhesives in automotive, aerospace, electronics, electrical, medical, sports, and construction sectors are also described. Finally, the article describes the steps in adhesive bonding, including storage and handling of adhesives, bonding preparation, adhesive application, tooling, and curing.