This article provides an overview of the finite-element-based analyses (FEA) of advanced composite structures and highlights key aspects such as the homogenization of materials properties and post-processing of numerical results. It discusses the analysis of composite structures based on micromechanics and macromechanics. The article describes the FEA of 3-D solid elements, 2-D cylindrical shell elements, and 1-D beam elements. It contains a table that lists the commercially available finite element codes related to the analysis of fibrous composite materials. The article presents classical examples of the mechanics of composite materials to illustrate the aspects of multilayered composite structures.

Finite element analysis is a computer-based numerical method for solving engineering problems in bodies of user-defined geometry. This article introduces the important issues of finite elements (especially accuracy and efficiency) in a nonacademic manner. It describes the Rayleigh-Ritz procedure for solving structural problems based on the principle of virtual work. The article discusses continuum elements, such as hexahedra, pentahedra, tetrahedra, quadrilaterals, and triangles, commonly used in three- or two-dimensional domains. It considers structural elements such as beam element, plate element, shell element, and elbow element. The article presents three examples to illustrate the types of problems that can be addressed and the decisions that must be made when using finite element analysis.

High-velocity gas motion occurs in and around the arc during welding. This article describes the phenomena of gas flow in gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW). The effect of trace element impurities on GTA weld penetration of selected alloys is presented in a table. The article concludes with a discussion on submerged arc welding (SAW).

This article briefly discusses popular techniques for metals characterization. It begins with a description of the most common techniques for determining chemical composition of metals, namely X-ray fluorescence, optical emission spectroscopy, inductively coupled plasma optical emission spectroscopy, high-temperature combustion, and inert gas fusion. This is followed by a section on techniques for determining the atomic structure of crystals, namely X-ray diffraction, neutron diffraction, and electron diffraction. Types of electron microscopies most commonly used for microstructural analysis of metals, such as scanning electron microscopy, electron probe microanalysis, and transmission electron microscopy, are then reviewed. The article contains tables listing analytical methods used for characterization of metals and alloys and surface analysis techniques. It ends by discussing the objective of metallography.

This article discusses the advantages, disadvantages, applications, and selection criteria of various technologies and transduction modalities that can generate and detect ultrasonic waves. These include piezoelectric transducers, electromagnetic acoustic transducers (EMATs), laser ultrasound phased array transducers, magnetostriction transducers, and couplants. The article discusses four basic types of search units with piezoelectric transducers. These include the straight-beam contact type, the angle-beam contact type, the dual-element contact type, and the immersion type. The article concludes with information on immersion or contact type focused search units.

Fluid flow is important because it affects weld shape and is related to the formation of a variety of weld defects in gas tungsten arc (GTA) welds. This article describes the surface-tension-driven fluid flow model and its experimental observations. The effects of mass transport on arc plasma and weld pool are discussed. The article reviews the strategies for controlling poor and variable penetration and describes the formation of keyhole and fluid flow in electron beam and laser welds. It also explains the fluid flow in gas metal arc welding and submerged arc welding, presenting its transport equations.

Particle-induced x-ray emission (PIXE) is one of several quantitative analyses based on characteristic x-rays. This article provides a detailed account on the principles of PIXE, discussing the data-reduction codes used to identify, integrate, and reduce x-ray peaks into elemental concentrations. It provides information on the calibration of PIXE analysis, which is mostly performed using gravimetric standards to avoid serious absorption, refluorescence, or ion energy change corrections. A comparative study on PIXE and x-ray fluorescence is also included. Finally, the article discusses the applications of PIXE in three areas, namely, atmospheric physics and chemistry, external proton milliprobes and historical analysis, and PIXE microprobes.

This article provides a detailed account of particle-induced x-ray emission (PIXE), covering the basic principles of PIXE analysis and calibration and quality-assurance protocols employed. A comparative study on PIXE and x-ray fluorescence is then presented. The article also discusses the applications of PIXE in atmospheric physics and chemistry, external proton milliprobes and historical analysis, and PIXE microprobes.

This article provides a schematic illustration of factors that should be considered in component design. It discusses the effect of component geometry on the behavior of materials and groups the main parameters that affect the value of the factor of safety. The article illustrates the estimation of probability of failure with an example. It reviews the designing and selection of materials for static strength and stiffness. The article also describes the causes of failure of engineering components, including design deficiencies, poor selection of materials, and manufacturing defects.

X-ray diffraction techniques are useful for characterizing crystalline materials, such as metals, intermetallics, ceramics, minerals, polymers, plastics, and other inorganic or organic compounds. This article discusses the theory of x-rays and how they are generated and detected. It also describes the crystalline nature of certain materials and how the geometry of a unit cell, and hence crystal lattice, affects the direction and intensity of diffracted x-ray beams. The article concludes with several application examples involving measurements on single and polycrystalline materials.

This article discusses the methods of analyzing the directional dependence of the mechanical properties of composites, especially those perpendicular to the major plane of the laminate. It provides a description of the common indirect load cases and direct out-of-plane load cases. The article concludes with a discussion on composite materials that are reinforced in the z-direction (also known as three-dimensional, or 3-D composites).

This article describes the operation and capabilities of surface analysis methods of metals, including scanning electron microscopy, electron probe microanalysis, transmission electron microscopy, secondary ion mass spectroscopy, and X-ray photoelectron spectroscopy. It provides information on the capabilities, typical uses, spatial resolution, elemental analysis detection threshold and precision, limitations, sample requirements, and operating principles of the scanning auger microprobe.

This article discusses the capabilities and limitations of various material characterization methods that assist in the selection of a proper analytical tool for analyzing particulate materials. Commonly used methods are microanalysis, surface analysis, and bulk analysis. The techniques used for performing microanalysis include scanning electron microscopy and electron probe X-ray microanalysis. The article describes surface analysis techniques, including Auger electron spectroscopy, X-ray photoelectron spectroscopy, and ion-scattering spectroscopy. Bulk analysis techniques, such as X-ray powder diffraction, inductively coupled plasma atomic emission spectroscopy, atomic absorption spectroscopy, and atomic fluorescence spectrometry, are also discussed.

Coatings and thin films can be studied with surface analysis methods because their inherently small depth allows characterization of the surface composition, interface composition, and in-depth distribution of composition. This article describes principles and examples of common surface analysis methods, namely, Auger electron spectroscopy, X-ray photoelectron spectroscopy, ion scattering spectroscopy, secondary ion mass spectroscopy, and Rutherford backscattering spectroscopy. It also provides useful information on the applications of surface analysis.

A sandwich structure is comprised of layered composite materials formed by bonding two or more thin facings or facesheets to a relatively thick core material. This article describes the sandwich panel failure modes. It tabulates the nomenclature and definitions for loads, geometry, and material properties. The article illustrates critical strength-check locations for a flat sandwich panel. It discusses the analysis methods formulated for flat rectangular honeycomb panels; curved sandwich panel; and for each of the various sandwich panel failure modes. The article concludes with a discussion on flat panel stability analysis methods.

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.

Several methods are developed for the numerical solution of partial differential equations, namely, meshed-solution methods such as the finite-element method (FEM), finite-difference method, and boundary-element method; and numerical algorithms consisting of so-called meshed-solution methods. This article introduces the methods of so-called meshed solutions, with an emphasis on the FEM. It presents some basic differential equations that are used to model the responses of structures, components, processes, or systems with emphasis on continuum mechanics. The article provides an outline on the mathematical principles of solving differential equations. It also reviews linear structural problems to illustrate the concept of the FEMs.