Electromagnetic signals at microwave and millimeter-wave frequencies are well suited for inspecting dielectric materials and composite structures in many critical applications. This article presents a partial list of reported nondestructive testing (NDT) application areas for microwaves. It discusses the advantages and limitations of inspection with microwaves. The article discusses the physical principles, including reflection and refraction, absorption and dispersion, scattering, and standing waves. It provides a discussion on terahertz (THz) imaging for nondestructive evaluation (NDE). The article concludes with information on ground-penetration radar (GPR) that uses electromagnetic radiation and detects the reflected signals from subsurface structures.

Microwaves (or radar waves) are a form of electromagnetic radiation with wavelengths between 1000 cm and 1 mm in free space. One of the first important uses of microwaves in nondestructive evaluation was for components such as waveguides, attenuators, cavities, antennas, and antenna covers (radomes). This article focuses on the microwave inspection methods that were subsequently developed for evaluation of moisture content in dielectric materials; thickness measurements of thin metallic coatings on dielectric substrates; and detection of voids, delaminations, macroporosity, inclusions, and other flaws in plastic or ceramic materials. It also discusses the advantages and disadvantages and the general approaches that have been used in the development of microwave nondestructive inspection.

This article presents an overview of the electric and magnetic parameters and discusses the significance of these parameters for electronic applications. It describes the components of analog and digital electronic circuits. The article reviews the augmenting technologies: magnetic and special technologies such as electrooptical.

Microwave and guided wave (GW) nondestructive evaluation (NDE) techniques are capable of detecting corrosion damage, cracks, and other defect types in inaccessible areas. This article describes the operation principles of the techniques and provides information on hidden corrosion detection and the applications of microwave NDE devices and GW ultrasonic NDE devices.

Thermal spray processes involve complete or partial melting of a feedstock material in a high-temperature flame, and propelling and depositing the material as a coating on a substrate. This article describes the properties of sprayed electronic materials, including dielectrics, conductors, and resistors, and discusses their implications and associated limitations for device applications and potential remedial measures. The article presents specific examples of electrical/electronic device applications, including electromagnetic interference/radio-frequency interference shielding, planar microwave devices, waveguide devices, sensing devices, solid oxide fuel cells, heating elements, electrodes for capacitors and other electrochemical devices.

This article addresses electrical testing and characterization of plastics and presents a number of techniques for evaluating the electrical properties of insulating materials, with a special focus on plastics, accompanied by a list of the electrical properties of different types of plastics. It provides the reader with sufficient information to select the appropriate electrical test(s) for a specific application. The tests covered in this article are widely used in industry to determine the electrical properties of insulating materials, particularly plastics. The article lists and defines terms used in connection with testing and specification of plastics for electrical applications.

In terms of their electrical properties, plastics can be divided into thermosetting and thermoplastic materials, some of which are conductive or semiconductive. This article provides detailed information on factors that affect the property of plastics. It discusses the major test methods used to determine the following dielectric properties of plastics: dielectric breakdown voltage, dielectric strength, dielectric constant, dissipation factor, arc tracking resistance, insulation resistance, volume, and surface resistivity or conductivity. The test specifications and conditions, recommended by several U.S. and foreign testing organizations for characterizing the electrical properties of plastic materials are listed. The article describes the influence of these properties on selection of plastics for insulation application. An outline of the electromagnetic shielding and testing methods of electromagnetic interference are also provided. Designations, electrical properties, and applications of elastomers are tabulated.

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.

This article provides an overview of the types, properties, and applications of traditional and advanced ceramics and glasses. Principal product areas for traditional ceramics include whitewares, glazes, porcelain enamels, structural clay products, cements, and refractories. Advanced ceramics include electronic ceramics, optical ceramics, magnetic ceramics, and structural ceramics.

This article discusses the attempts made by the industry to create sensing approaches for modeling a process, part, and chemistry and kinetics. It reviews microwave curing of thick-section composites and the resin cure sensors that are used for resin cure monitoring. These include dielectric cure sensors, fiberoptics-based resin cure sensors, ultrasonics-based resin cure sensors, and dosimetry-based resin cure sensors. The article provides information on the resin cure control flow sensing, flow modeling, flow mapping, and resin flow. It addresses some practical issues in sensing resin cure and flow.

Ceramic materials serve important insulative, capacitive, conductive, resistive, sensor, electrooptic, and magnetic functions in a wide variety of electrical and electronic circuitry. This article focuses on various applications of advanced ceramics in both electric power and electronics industry, namely, dielectric, piezoelectric, ferroelectric, sensing, magnetic and superconducting devices.

This article discusses the use of a shaped electrode for electrical discharge machining (EDM). It describes the operational methodology of the EDM. Topography, metallurgical and chemical effects, and surface integrity of the EDM surface are reviewed. The article provides information on the characteristics of electrodes and the process features of electrode manufacturing. Functions of the dielectric fluids and applications of the EDM are discussed. The article reviews the advancement in EDM such as no-wear EDM and computer numerically controlled vertical EDM. It analyzes the applications and process of the traveling wire EDM. Health and safety measures for the EDM process are also discussed.

Engineering plastics offer unique product benefits based on physical properties, or combinations of physical properties, that allow vastly improved product performance. Providing an overview of the general characteristics and the mechanical and environmental stress response of engineering plastics, this article discusses various factors, including thermal, mechanical and electrical properties, environmental factors, and material cost that are important in the selection of engineering plastics for specific applications.

This article is a collection of tables that present information on the physical properties of periodic table elements, and maximum service temperatures, dielectric constants and typical dielectric properties of selected nonmetallic materials.

Electrical discharge grinding (EDG) is much like electrical discharge machining except that the electrode (tool) is a rotating graphite wheel. This article commences with a schematic illustration of a setup for EDG wheels and discusses the control operation of the EDG setup. It tabulates typical applications and conditions for the EDG of stainless steels using 300 mm diameter wheels. The article describes the process characteristics of the EDG in terms of applications, surface finish, corner radius, and wheel wear. It concludes with a graphical illustration of the effect of heat in electrical discharge grinding on the surface hardness of various work metals.

The electrical discharge machining (EDM) process is used for machining dies because of its ability to machining difficult geometries or materials with poor machinability. This article provides a discussion on the fundamentals of electrical discharge erosion and the principles of EDM and orbital-movement EDM. It discusses various aspects of wire EDM in machining dies and provides an overview of the materials used in EDM electrodes. The article concludes with a discussion on electrochemical machining.

This article provides an overview of the various types of unsaturated polyester resins and low-profile additives. The resins include general-purpose resins, isophthalic resins, bisphenol A fumarate resins, chlorendic resins, and vinyl ester resin. The article describes the mechanical and electrical properties, thermal and oxidative stability, and chemical and ultraviolet (UV) resistance of polyester resins. It concludes with a discussion on the flame-retardant polyester resins.