This article explores why structural element and subcomponent testing are conducted. It discusses the different types of failure modes in composites, and provides information on the testing methodology, fixturing, instrumentation, and data reporting. The article reviews various standard elements used to characterize composite materials for the various failure modes. Simple structural-element testing under in-plane unidirectional, multidirectional, and combined loading, as well as out-of-plane loading are discussed. Simple bolted and bonded joints, as well as data correlation are reviewed with analytical predictions. The article also provides a list of the ASTM testing standards applicable at the element level of testing for both polymer-matrix composites and metal-matrix composites. It concludes with a discussion on durability and damage tolerance testing.

This article presents the failure of polymer-matrix composites and the methodology for fractography. It provides a detailed discussion on the types of translaminar, interlaminar, and intralaminar failures. The article also presents a discussion on the types of fatigue failures, and the influence of composite architecture. It provides details of the fractography associated with defects and damage.

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.

This article describes the types of fabrics and preforms used in the manufacture of advanced composites and related selection, design, manufacturing, and performance considerations. The types of fabrics and preforms include unidirectional and two-directional fabrics; multidirectionally reinforced fabrics; hybrid fabrics; woven fabric prepregs; unidirectional and multidirectional tape prepregs; and the prepreg tow. The article discusses three major categories of tape manufacturing processes, namely, the hand lay-up, machine-cut patterns that are laid up by hand, and the automatic machine lay-up. It provides a description of the two classes of prepregs. These include those that are suitable for high-performance applications and suitable for lower-performance molding compounds.

Testing of fiber-reinforced composite materials is performed to determine uniaxial tensile strength, Young's modulus, and Poisson's ratio relative to principal material directions, that helps in the prediction of the properties of laminates. Beginning with an overview of the fundamentals of tensile testing of fiber-reinforced composites, this article describes environmental exposures that often occur during specimen preparation and testing. These include exposures during specimen preparation, and planned exposure such as moisture, damage (impact), and thermal cycling techniques. The article also discusses the test procedures, recommended configurations, test specimen considerations, and safety requirements considered in the four major types of mechanical testing of polymer-matrix composites: tensile test, compression test, flexural test, and shear test.

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.

This article describes the interaction of composition, manufacturing process, and composite properties of composites. The manufacturing process includes resin-matrix, metal-matrix, and carbon/carbon matrix processing. The article discusses various mechanical properties of composites. It explores how variations in the composition, manufacturing, shop process instructions, and loading/environmental conditions can affect the use of a composite product in a performance/service life operation.

This article presents a comprehendable and comprehensive physics-based approach for characterizing the strength of fiber-reinforced polymer composites. It begins with background information on the goals and attributes of this method. The article then addresses the characterization of fiber failures in laminates, because these are at the highest strengths that can be attained and, therefore, are usually the design objective. An exception would be if the design goal is to maximize energy absorption, rather than static strength. The discussion proceeds to situations in which the matrix fails first, either by intent, by design error, or because of impact damage. The state of the modeling propagation and arrest of matrix damage follows. Comparisons of this physics-based approach are then made to empirically based failure theories.

Control of grain flow is one of the major advantages of shaping metal parts by rolling, forging, or extrusion. This article shows the effects of anisotropy on mechanical properties. Cylindrical forgings commonly have a straight parting line located in a diametral plane. The alternate classes of parting lines are called either "straight" or "broken" for brevity. Regardless of whether draft is applied or natural, the forging will have its maximum spread or girth at the parting line. Proper placement of the parting line ensures that the principal grain flow direction within the forging will be parallel to the principal direction of service loading. The article reviews the mutual dependence of parting line and forging process. It provides a checklist for the forging designer that suggests a systematic approach for establishing parting line location. Finally, the article contains examples, with illustrations of parting line locations, accompanied by tables of design parameters.

Solidification of cast iron alloys brings about volumetric changes. This article describes direct measurements of volume changes with an illustration of the analysis of volumetric changes during solidification of cast iron with the use of a specially designed riser combined with a furnace. It provides a discussion on the dilatometer analysis that is generally used to measure linear displacement as a function of temperature for all types of materials, and the problems associated with volume-change measurements. The article presents a graphical representation of a consequence of the anisotropy, where the calculated volume change is illustrated as a function of temperature. It concludes with a review of kinetic of graphite expansion.

This article provides the general mechanical testing guidelines for the characterization of lamina and laminate properties. Guidelines are provided for tensile property, compressive property, shear property, flexure property, fracture toughness, and fatigue property test methods. The article also tabulates selected standards for lamina and laminate mechanical testing.

Pultrusion is an automated process for manufacturing composite materials into continuous, constant cross-sectional profiles. The article provides an overview of the pultrusion process and the wide range of materials that can be used to provide a broad spectrum of composite properties. It discusses the mechanical, physical and material properties of pultruded products, and the orientation options available to utilize the properties advantageously. The article also provides guidelines for designing pultruded products.

This article discusses the presses, auxiliary equipment, and dies used in the blanking and piercing of commonly used magnetically soft materials, namely, low-carbon electrical steels and oriented and nonoriented silicon electrical steels. It describes the effect of stock thickness and work metal composition and condition on blanking and piercing. The article provides an overview of the influence of burr height on stacking factors and presents a discussion on the lubrication and core plating of electrical steels that ease the process.

In the design of composite structures for durability and damage tolerance, the primary concerns are out-of-plane failures, such as delamination, material degradation associated with environment, stability under compression loading, large degree of scatter in fatigue life, and bearing failure of joints. This article presents an introductory discussion on the fatigue damage process, methodologies assessing fatigue behavior, and life prediction models. It describes the damage mechanisms introduced for a quasi-isotropic laminate under tension-compression fatigue loading. Delamination is a critical issue in fatigue and generally results from high interlaminar normal and shear stresses. The article schematically illustrates the structural elements in which high interlaminar stresses are common. It concludes with a discussion on the classification of fatigue models such as mechanistic or phenomenological, for composite materials under cyclic loading.

Detailed analyses and test correlations are typically required to support design development, structural sizing, and certification. This article addresses issues concerning building block levels ranging from design-allowables coupons up through subcomponents, as these levels exhibit a wide variety of test-analysis correlation objectives. At these levels, enhanced analysis capability can be used most effectively in minimizing test complexity and cost while also reducing design weight and risk. The article discusses the examples of tests for which good correlative capability has shown significant benefit. These include notched (open and/or filled hole) tension and compression, inter/intralaminar shear and tension, and pin bearing.

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.

Most surfaces have regular and irregular spacings that tend to form a pattern or texture on the surface. This article provides information on the general background of surface topography and discusses the different methods for measuring surface topography, namely, contact and noncontact techniques, and the focus-follow method. Examples of different types of parameters obtained and how they are applied can best be described by discussing the various types of surfaces generated by finishing methods. The surfaces include ground, turned, and milled machined surfaces; surfaces subjected to stress; bearing surfaces; plateau honed and tapped surfaces; and reflective, painted, elastic, and wear-resistant surfaces.

This article discusses the requirements that are typically considered in designing a steel casting. It describes the materials selection that forms a part of process of meeting the design criteria. The article provides information on the material selection guide for five major design applications. It examines the attributes that are specific to the manufacturing of steel castings. The article concludes with information on the various nondestructive examination methods available for ensuring manufacturing quality and part performance in steel castings.

Knowledge of fatigue behavior at the laminate level is essential for understanding the fatigue life of a laminated composite structure. This article describes fatigue failure of composite laminates in terms of layer cracking, delamination, and fiber break and interface debonding. It discusses the fatigue behavior of composite laminates in the form of a relation between applied maximum fatigue stress and fatigue life. The article explains Weibull distribution and parameters estimation for fatigue data analysis and life prediction of composite laminates. It analyzes the fatigue properties and damage tolerance of fiber-metal laminates such as ARALL and GLARE laminates. The article concludes with a discussion on the effects of fatigue on notched and unnotched specimens.

Steel castings can be made from any of the many types of carbon and alloy steel produced in wrought form. They are divided into four general groups according to composition. Carbon and low-alloy steel castings can meet a wide range of application requirements because composition and heat treatment can be selected to achieve specific combinations of properties, including hardness, strength, ductility, fatigue, and toughness. This article discusses physical, mechanical, and engineering properties as well as fatigue properties and the effects of section size and heat treatment. Highly stressed steel castings for aircraft and for high-pressure or high-temperature service must pass rigid nondestructive inspection.