The design and analysis of aerospace and industrial composite components and assemblies requires a detailed knowledge of materials properties, which, in turn, depend on the manufacturing, machining, and assembly methods used. This article, through several tables and graphs, provides the mechanical properties, physical properties, and service characteristics of representative composite fiber-resin combinations, including thermoplastic matrix composites such as thermoplastic polyester resins, thermoplastic polyamide resins, and thermoplastic polysulfone resins, and thermoset matrix composites such as thermoset polyester resins, thermoset phenolic resins, thermoset epoxy resins, thermoset polyimide resins, and thermoset bismaleimide resins.

The selection of engineered materials is an integrated process that requires an understanding of the interaction between materials properties, manufacturing characteristics, design considerations, and the total life cycle of the product. This article classifies various engineered materials, including ferrous alloys, nonferrous alloys, ceramics, cermets and cemented carbides, engineering plastics, polymer-matrix composites, metal-matrix composites, ceramic-matrix and carbon-carbon composites, and reviews their general property characteristics and applications. It describes the synergy between the elements of the materials selection process and presents a general comparison of material properties. Finally, the article provides a short note on computer aided materials selection systems, which help in proper archiving of materials selection decisions for future reference.

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.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of a type of resin-matrix composites, carbon-epoxy composites. The fractographs illustrate the fracture modes found in composite prepregs, composite panels, solid rocket motor nozzles, and tension, flexural, compressive, and shear loadings.

Relatively limited effort has gone into developing repair processes and materials for composites, in contrast to the significant labor and expense that has gone into the development of these materials for numerous critical applications. As composites gain wider acceptance as aerospace materials, there is a need to understand the requirements of the end users regarding repair of these advanced materials. This article focuses on the repair of graphite-epoxy structures designed in a variety of forms for a wide range of load intensities. Five repair concepts developed for generic laminate repair have been validated in this article through the required environmental and load condition tests. These include bonded-scarf joint flush repair, double-scarf joint flush repair, blind-side banded-scarf repair, blind-side sandwich repair, and bonded external patch repair. A brief note on thermoplastic repair concepts is also provided in this article.

Ultrasonic inspection is a nondestructive technique that is useful in both quality control and research applications for flaw detection in fiber-reinforced composite materials. This article describes ultrasonic nondestructive analysis by outlining its three basic types of scans. It reviews the important quality control techniques used during the manufacture of composite components by analyzing tooling control, material control, pattern orientation control, and in-process control.

The structural efficiency of a composite structure is established by its joints and assembly. Adhesive bonding, mechanical fastening, and fusion bonding are three types of joining methods for polymer-matrix composites. This article provides information on surface treatment and the applications of adhesive bonding. It discusses the types of adhesives, namely, epoxy adhesives, epoxy-phenolic adhesives, condensation-reaction PI adhesives, addition-reaction PI adhesives, bismaleimide adhesives, and structural adhesives. The article provides information on fastener selection considerations, including corrosion compatibility, fastener materials and strength, head configurations, importance of clamp-up, interference fit fasteners, lightning strike protection, blind fastening, and sensitivity to hole quality. Types of fusion bonding are presented, namely, thermal welding, friction welding, electromagnetic welding, and polymer-coated material welding.

Acoustic emission is the generation of stress waves by sudden movement in stressed materials. This article begins with a comparison of acoustic emission from most other nondestructive testing (NDT) methods, and discusses the range of applicability of acoustic emission. It describes the instrumentation principles of acoustic emission and reviews the role of acoustic emission in materials studies. The article illustrates the testing of metal-matrix composites (MMCs) using acoustic emission and the use of acoustic emission inspection in production quality control. It concludes with information on the structural test applications of acoustic emission inspection to find defects and to assess or ensure structural integrity.

Autoclave molding is a process used to impart a controlled heat and pressure cycle cure to a layup. This article describes the materials used for preparing a layup, including peel ply, separator, bleeder, barrier, breather, dam, and vacuum bag. It describes the major elements and functions of an autoclave system, including pressure vessel, gas stream heating and circulation sources, gas stream pressurizing systems, vacuum systems, control systems, and loading systems. The article includes information about modified autoclaves for specialized applications and safety practices in autoclave molding. It also describes the tooling configuration and type of tooling which includes aluminum and steel tooling, electroformed nickel tooling, graphite-epoxy tooling, and elastomeric tooling.

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.

Honeycomb is a product consisting of very thin sheets attached to form connecting cells. This article briefly explains the construction, core characteristics, properties, and testing methods of the honeycomb structures. It discusses the special processes used to custom fit the shape of core to fit customer’s specific needs. The article provides information on sandwich structures, including material selection, design guidelines, and structural efficiency.

Wet lay-up using hand or spray techniques is one of the simplest methods of combining a fiber reinforcement with a solidifying resin to form a composite structure. This article describes several wet lay-up processes - including contact molding, spray molding, vacuum bag molding, and autoclave molding - suited for making parts on open-faced molds using polyester and vinyl ester resins. The article also provides information on mechanically assisted lay-up which can be automated to alleviate some of the manual work.

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.

A thermosetting resin, or thermoset, is a synthetic organic polymer that cures to a solid, infusible mass by forming a three-dimensional network of covalent chemical bonds. Significant applications include construction and thermoset engineering plastics. This article discusses the general and family characteristics of thermosetting resin families, including allyls, aminos (urea formaldehyde and melamine formaldehyde), cyanates, epoxies, polybenzimidazoles, unsaturated polyesters, thermoset polyimides, phenolics, and vinyl esters. It also explains processing methods, including curing and curing agents. The article provides descriptions of commercial product forms and the wide array of applications of thermosetting resins. It also tabulates the performance properties (mechanical, thermal, electrical and chemical resistance) of some families of unfilled or unreinforced thermosetting resins and reinforced or filled grades.

This article describes the use of conventional machining techniques, laser cutting and water-jet cutting for producing finished composite parts. It explains two representative polymer-matrix composites--graphite and aramid composites--and discusses the machining and drilling problems such as delamination and fiber or resin pullout. The article describes machining and drilling techniques and the necessary tools and cutting parameters. It presents a description of laser cutting. The article also provides information on the advantages, disadvantages, cutting characteristics, and applications of water-jet cutting and abrasive water-jet cutting.

Bulk molding compounds can be molded into a variety of complex shapes by methods that can be readily automated for high volume production. This article describes the formulation and processing (compound formation, and molding methods) of bulk molding compounds. It discusses the effects of fiber type, fiber length, and matrix type on thermoset bulk molding compounds. The markets for long-fiber-reinforced bulk molding compounds are electrical, ordnance, aerospace, industrial, sporting goods, and automotive.

Braiding is a textile process that is known for its simplicity and versatility. Braided structures are unique in their high level of conformability, torsional stability, and damage resistance. This article describes the braiding process and the mechanical properties of two-dimensional and three-dimensional braiding.

Thermal analysis provides a powerful tool for researchers and engineers in determining both unknown and reproducible behavioral properties of polymer molecules. This article covers the thermal analysis and thermal properties of engineering plastics with respect to chemical composition, chain configuration, conformation of the base polymers, processing of the base polymers with or without additives; and the response to chemical, physical, and mechanical stresses of base polymers as unfilled, shaped articles or as components of composite structures. It also describes thermal analysis techniques, including differential scanning calorimetry, thermogravimetric analysis, thermomechanical analysis, and rheological analysis. This article also summarizes the basic thermal properties used in the application of engineering plastics, such as thermal conductivity, temperature resistance, thermal expansion, specific heat, and the determination of glass transition temperatures. It concludes with a discussion of the thermal and related properties of nine thermostat resin systems divided into three groups by low, medium, and high service temperature capabilities.