Analysis and Performance of Fiber Composites

Bhagwan D. Agarwal, Lawrence J. Broutman, K. Chandrashekhara

• Publisher: Wiley
• Year: 2017
• ISBN:
  9781119389972
• Edition: 4
• Topic: Technik & Maschinenbau
• Subtopic: Maschinenbau

Updated and expanded coverage of the latest trends and developments in fiber composite materials, processes, and applications

Analysis and Performance of Fiber Composites, Fourth Edition features updated and expanded coverage of all technical aspects of fiber composites, including the latest trends and developments in materials, manufacturing processes, and materials applications, as well as the latest experimental characterization methods.

Fiber reinforced composite materials have become a fundamental part of modern product manufacturing. Routinely used in such high-tech fields as electronics, automobiles, aircraft, and space vehicles, they are also essential to everyday staples of modern life, such as containers, piping, and appliances. Little wonder, when one considers their ease of fabrication, outstanding mechanical properties, design versatility, light weight, corrosion and impact resistance, and excellent fatigue strength. This Fourth Edition of the classic referencethe standard text for composite materials courses, worldwideoffers an unrivalled review of such an important class of engineering materials.

Still the most comprehensive, up-to-date treatment of the mechanics, materials, performance, analysis, fabrication, and characterization of fiber composite materials available, Analysis and Performance of Fiber Composites, Fourth Edition features:

• Expanded coverage of materials and manufacturing, with additional information on materials, processes, and material applications
• Updated and expanded information on experimental characterization methodsincluding many industry specific tests
• Discussions of damage identification techniques using nondestructive evaluation (NDE)
• Coverage of the influence of moisture on performance of polymer matrix composites, stress corrosion of glass fibers and glass reinforced plastics, and damage due to low-velocity impact
• New end-of-chapter problems and exercises with solutions found on an accompanying website
• Computer analysis of laminates

No other reference provides such exhaustive coverage of fiber composites with such clarity and depth. Analysis and Performance of Fiber Composites, Fourth Edition is, without a doubt, an indispensable resource for practicing engineers, as well as students of mechanics, mechanical engineering, and aerospace engineering.

Visit the Companion Website at: https://www.wiley.com/WileyCDA/Section/id-830336.html

1
INTRODUCTION

1.1 DEFINITION

The word composite means “consisting of two or more distinct parts.” Thus, a material having two or more distinct constituent materials or phases may be considered a composite material. However, we recognize materials as composites only when the constituent phases have significantly different physical properties, and thus the composite properties are noticeably different from the constituent properties. The difference in properties will be more obvious when the properties of one constituent are much greater (≥5 times) than the other, when this phase is in fiber or platelet form, and its volume fraction is greater than 10%. Many combinations of constituents do not result in a new material with significantly different properties. Such materials are not classified as composites. For example, common metals almost always contain unwanted impurities or alloying elements; plastics generally contain small quantities of fillers, lubricants, ultraviolet absorbers, and other materials for commercial reasons such as economy and ease of processing, yet these generally are not classified as composites. In the case of metals, the constituent phases often have nearly identical properties (e.g., modulus of elasticity), the phases are not generally fibrous in character, and one of the phases usually is present in small-volume fractions. Thus, the modulus of elasticity of a steel alloy is insensitive to the amount of the carbide present, and metallurgists generally have not considered metal alloys as composites, particularly from the point of view of analysis. Nevertheless, two-phase metal alloys are good examples of particulate composites in terms of structure. Although plastics, which are filled with small amounts of additives to reduce cost, are composites, they need not be considered as such if their physical properties are not greatly affected by the additives.

Within the wide range of composite materials, a definition may be adopted to suit one's requirements. For the purpose of discussion in this book, composites can be considered to be materials consisting of two or more chemically distinct constituents, on a macroscale, having a distinct interface separating them. This definition encompasses the fiber composites, which are of primary interest in this text. This definition also encompasses many other types of composites that are not treated specifically in this book.

1.2 CLASSIFICATION

Composites consist of one or more discontinuous phases embedded in a continuous phase. The discontinuous phase usually has higher stiffness and strength than the continuous phase and is called the reinforcement or reinforcing material, whereas the continuous phase is termed the matrix. Ceramic matrix composites could be exceptions since matrix may have higher stiffness than the reinforcement. Properties of composites are strongly influenced by the properties of constituent materials, their distribution, and the interaction among them. Therefore, proper description of a composite material as a system requires, besides the constituent materials and their properties, the geometry of the reinforcement (shape, size, and size distribution) and its concentration, concentration distribution, and orientation with reference to the system.

Most composite materials have, so far, been developed to improve mechanical properties such as strength, stiffness, toughness, and high-temperature performance. The mechanism of improving these properties strongly depends on the geometry of the reinforcement. Therefore, it is quite convenient to classify composite materials on the basis of the microstructure of a representative unit of reinforcement to study together the composites that have a common strengthening mechanism. Figure 1.1 represents a commonly accepted classification scheme for composite materials. With regard to this classification, the distinguishing characteristic of a particle is that it is nonfibrous in nature with all its dimensions approximately equal. It may be spherical, cubic, tetragonal, a platelet, or of other regular or irregular shape. A fiber is characterized by its length being much greater than its cross-sectional dimensions. Particle-reinforced composites are sometimes referred to as particulate composites. Fiber-reinforced composites are, understandably, called fiber composites.

Figure 1.1. Classification of composite materials.

1.3 PARTICULATE COMPOSITES

Particle-reinforced composites are called particulate composites. A particle generally has no long dimension, with the exception of platelets. The dimensions of the reinforcement determine its capability of contributing its properties to the composite. Also, a reinforcement with a long dimension inhibits the growth of cracks normal to the reinforcement that otherwise might lead to failure, particularly with brittle matrices. Therefore, particles, in general, are not very effective in improving fracture resistance. However, particles of rubberlike substances in brittle po...