Design and Analysis of Composite Structures: With Applications to Aerospace Structures, 2nd Edition

3

Review of Classical Laminated Plate Theory

This chapter gives some basic laminate definitions and a brief summary of the classical laminated-plate theory (CLPT). Aspects of CLPT, in particular, the laminate stiffness matrices are used throughout the remainder of this book.

3.1 Composite Materials: Definitions, Symbols and Terminology

A composite material is any material that consists of at least two constituents. In this book, the term ‘composite material’ refers to a mixture of fibres and matrix resulting in a configuration that combines some of the best characteristics of the two constituents. There is a large variety of possible combinations. For fibres, some of the options include, E- or S-glass, quartz, graphite, Kevlar®, boron, silicon, etc., appearing in long continuous or short discontinuous form. The matrix materials cover a wide range of thermoset (epoxy, polyester, phenolics, polyimides, bismaleimids) or thermoplastic resins or metals such as aluminium or steel. The building block of a composite material is the ply or lamina. Plies or laminae are stacked together (different orientations and materials can be combined) to make a laminate.

The most common plies used are unidirectional plies (where all fibres are aligned in one direction) or fabric plies (plain weave, satins, etc.) where fibres are oriented in two mutually perpendicular directions. If each ply in the stacking sequence or layup making up a laminate is denoted by its orientation θ (in degrees) relative ...