Search Results for hygrothermal behavior

Hygrothermal behavior of cured composite materials relates to the combined and commonly synergistic effects of moisture absorption and temperature on various physical, chemical and mechanical properties. This article focuses on the influence of resins or matrices, reinforcements, processing, and diffusion on hygrothermal behavior of polymer-matrix composites and provides an outline on general considerations in assessing them. It discusses the hygrothermal testing and conditioning of polymer-matrix composites to assess fundamental hygrothermal behavior. The article provides information on the accelerated aging process for understanding the degradation mechanisms and failure modes in composites. It also describes the effect of moisture absorption on mechanical properties of polymer-matrix composites.

This article focuses on the unique characteristics of composites and laminated plates, including orthotropic, anisotropic, and unsymmetric plates. It discusses the stability issues associated with practical, structural laminates based on the finite stack effects and transverse shear stiffness effects. The article presents the study of instability associated with postbuckling behavior and hygrothermal buckling in composite sandwich panels and shell panels.

Composite materials offer amazing opportunities for delivering structures that are optimized to meet design requirements. This article provides a summary of the concepts discussed in the articles under the section “Engineering Mechanics, Analysis, and Design” in ASM Handbook, Volume 21: Composites. The section introduces many of the engineering approaches used in composite industry.

This article begins with a discussion on fiber-reinforced composite materials and describes the generic behavior and structure/property relationships of composites. The article summarizes lamina properties and presents equations that help in the calculation of lamina properties. Composite laminates are constructed from lamina with uniaxial fiber orientation and frequently from textile fabrics as well. The article explains the characteristics of symmetric in-plane and through-thickness laminates; asymmetric in-plane and symmetric through-thickness laminates; asymmetric laminates; and curved laminates. It provides information on controlled thermal expansion composites, metal-matrix composites, and ceramic-matrix composites. The article illustrates the types of bonded joints and concludes with a discussion on design for manufacturing.

This article discusses the need for design allowables, development of design allowables, and important factors that affect the selection of the allowable. It provides a comparison between lamina and laminate allowables. The article discusses laminate results and specific techniques used in the statistical development of allowable values.

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.

A unidirectional fiber composite (UDC) consists of aligned continuous fibers that are embedded in a matrix. This article describes a variety of analytical methods that are used to determine the various physical properties of the UDC. These properties include elasticity, thermal expansion coefficients, moisture swelling coefficients, static and dynamic viscoelastic properties, conductivity, and moisture diffusivity.

Characterization of nonmechanical properties is performed in the testing and certification of composite materials. This article focuses on the properties of composites that are commonly investigated. The properties include: per ply thickness; constituent content; density; coefficient of thermal expansion and coefficient of moisture expansion; glass transition temperature; thermal conductivity, diffusivity, and specific heat.

This article describes the role of the full-scale testing in assessing composite structural systems of aircraft and qualifying them for in-service use. The typical full-scale tests include static, durability, and damage tolerance. The article discusses the parameters to be considered when developing the basic requirements for the static test. These parameters consist of material considerations, moisture and temperature effects, structure size, load application alternatives, instrumentation requirements, test procedure considerations, ultimate load requirements, and test results correlation. The basic requirements common for durability and damage tolerance tests, including environmental effects and inspection requirements, are also discussed.

This article describes the failure analysis procedures for composites and the techniques to be used in these analyses. These procedures include a review of the available in-service records, materials and processing methods, print requirements, and manufacturing records; visual analysis and nondestructive part evaluation; and verification of materials and processing methods. The article discusses the determination of fiber, matrix, and void volume fractions and verification of ply lay-up and orientation. A review of composites processing parameters; fractography and surface analysis; and mechanical testing and stress analysis is also presented.

This article provides an overview of the physics and math associated with moisture-related failures in plastic components. It develops key equations, showing how they are used to analyze the causes and effects of water uptake, diffusion, and moisture concentration in polymeric materials and resins. It explains how absorbed moisture affects a wide range of properties, including glass transition temperature, flexural and shear modulus,creep, stress relaxation, swelling, tensile and yield strength, and fatigue cracking. It provides relevant data on common polymers, resins, and fiber-resin composites.

This article provides non-proprietary and non-competition-sensitive information related to aircraft applications. It presents an overview of reliability and commonly used measurements. Failure modes that cause the negative performance are reviewed based on many types of sources. These include manufacturer service bulletins, reliability and customer service departments, literature reviews, demonstration programs, in-service evaluations, design guides, and surveys of commercial and military aircraft maintenance organizations. The article also describes lessons learned while attempting to avoid overlapping maintainability, reparability, and materials choice.

Cyanate ester resins are a family of high-temperature thermosetting resins that bridge the gap in thermal performance between engineering epoxy and high-temperature polyimides. This article discusses the chemistry, properties and characteristics of the cyanate ester resins. It describes the processing procedures for the cyanate ester resins and provides information on properties for selected applications, such as space applications, radomes, and printed circuit boards.

Accelerated life testing and aging methodologies are increasingly being used to generate engineering data for determining material property degradation and service life (or fitness for purpose) of plastic materials for hostile service conditions. This article presents an overview of accelerated life testing and aging of unreinforced and fiber-reinforced plastic materials for assessing long-term material properties and life expectancy in hostile service environments. It considers various environmental factors, such as temperature, humidity, pressure, weathering, liquid chemicals (i.e., alkalis and acids), ionizing radiation, and biological degradation, along with the combined effects of mechanical stress, temperature, and moisture (including environmental stress corrosion). The article also includes information on the use of accelerated testing for predicting material property degradation and long-term performance.

This article begins with a discussion on the criteria for evaluating computer programs for composites structural analysis, including database capabilities, types of engineering calculations supported, interface and operating systems, and technical support. It describes the capabilities of programs, such as CompositePro, ESAComp, and V-Lab that provide a graphical interface, built-in databases, and integrated modules for the different types of analyses. The article reviews the modules of other programs used for composite analysis. The programs include ASCA, CADEC, CoDA, COMPASS, ESDU, LAP, PROMAL, and SACL. The article concludes with information on on-line programs and recourses.

This article presents a comprehensive collection of the definition of terms related to metallurgy.