Mechanics Of Composite Structures

V.V. Vasiliev

• Publisher: CRC Press
• Year: 2017
• Print ISBN: 9781560320340
• eBook ISBN: 9781351432559
• Topic: Physical Sciences
• Subtopic: Civil Engineering

This book compiles techniques used to analyze composite structural elements ranging from beams through plates to stiffened shells. The content is suitable for graduate-level students with a basic background in mechanics of composite materials. Moreover, this book will be placed in an active spot on the bookshelves of composite structures designers as well as researchers.

Chapter 1

INTRODUCTION TO STRUCTURAL PROPERTIES OF COMPOSITE MATERIALS

A composite material is a nonhomogeneous material having two or more components including reinforcing elements that provide necessary mechanical characteristics of the material and a matrix that allows uniform deformation of the reinforcements. The mechanical behavior of a composite material is determined by the properties of reinforcements and the matrix as well as by the adhesive strength at their interfaces. The properties of the composite material depend on those of the initial components and the methods used to combine them in one material. Different matrices and reinforcements can be combined to synthesize composite materials possessing both the properties of the initial components and also some new valuable characteristics. For example, interfaces between the reinforcements and the matrix substantially increase the fracture toughness of the material. Therefore, in contrast to metals, in composite materials, an increase in the static strength results, as a rule, and an increase in fracture toughness according to Mileiko [1]. In the following, we consider the main properties of reinforcements, various matrices, and composite materials made from them.

1.1 FIBERS

In modern composite materials, extensive use is made of thin, 5-200 × 10⁻⁶m in diameter, continuous or chopped fibers playing the part of reinforcements themselves or providing the basis for producing yarns, yarn bundles, and cloth of various weave types. Fibers must meet a set of operational and technical conditions. These requirements are imposed on their strength, stiffness, density, and stability during their operating life. Processability of fibers allows the development of efficient manufacturing processes. One more important requirement is the compatibility of fibers with the matrix material. Components are considered to be compatible if the adhesive strength at their interface is close to the matrix strength. Now consider the basic types of fibers.

1.1.1 Glass Fibers

Continuous glass fibers are 3-20 × 10⁻⁶m in diameter and are characterized by 2-6 GPa tensile strength, 50-100 GPa modulus of elasticity, and 2400-2600 kg/m³ density. The strength of such glass fibers essentially depends on temperature. With a decrease in temperature down to −196°C, the tensile strength increases by a factor of 1.5-2.0. Increasing the temperature decreases the tensile strength, especially below 300°C. The stiffness of glass fibers decreases only slightly with temperature rise up to the softening point.

In 1920, Griffith used glass fibers in the experiments that gave rise to mechanics of brittle fracture [2]. He established the major property of thin fibers – their high tensile strength in comparison with monolithic materials. As is well known, the strength of a material predicted with solid state physics considerably exceeds the experimental strength of real materials. In particular, the calculated tensile strength of glass was estimated by Griffith as 14 GPa, whereas the tensile strength of glass rods 1 × 10⁻³m in diameter turned out to be 1...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Translation Editor’s Preface
• Chapter 1 INTRODUCTION TO STRUCTURAL PROPERTIES OF COMPOSITE MATERIALS
• Chapter 2 EQUATIONS OF COMPOSITE STRUCTURE MECHANICS
• Chapter 3 COMPOSITE BEAMS, COLUMNS, AND RINGS
• Chapter 4 THIN-WALLED BEAMS
• Chapter 5 COMPOSITE PANELS AND PLATES
• Chapter 6 CIRCULAR CYLINDRICAL SHELLS
• Chapter 7 AXISYMMETRIC DEFORMATION OF SHELLS OF REVOLUTION
• References
• Index