Chapter 2 - Fundamentals of aerospace composite materials

Abstract

This chapter is dedicated to the discussion of fundamental aspect of composite materials. The basic principles and notations of anisotropic elasticity theory are reviewed in tensor notations and in Voigt matrix notations. Strain–displacement and stress–strain relations, equation of motion in terms of stresses, and equation of motion in terms of displacements are introduced. Attention is next focused on the unidirectional (UD) composite lamina: formulae for the estimation of lamina elastic properties from the properties of the constituent fiber and matrix were presented in principal axes. The elastic constants in the longitudinal, transverse, in-plane shear, and transverse shear directions are deduced and the corresponding stiffness and compliance matrices are presented and related to the constitutive fiber and matrix properties. The induced-strain effects associated with thermal, hygroscopic, and piezoelectric effects as well as combinations thereof are discussed. The properties of the rotated UD lamina are considered next. The 3D rotation principles are reviewed and then applied to obtain the rotated strain, stress, stiffness, and compliance matrices. Composite failure is analyzed, failure modes are discussed and various failure criteria are presented and compared. A large number of worked-out examples are given, as well as associated problems and exercises.