TABLE OF CONTENTS The whole subject of composite materials is beyond the scope of the present text, and only some very basic key concepts are introduced in this appendix. Most of the material in this appendix is condensed from Tsai and Hahn. The interested reader is directed to this work and other referenced texts for a more in-depth treatment of the subject. Furthermore, only those topics that relate directly to composite blade construction are treated herein. Also, discussion is limited to only "symmetric" composites.
Except for exotic metal alloys most metals are completely isotropic in that they have the same properties in any direction. That is, their basic properties are invariant in all three dimensions. Moreover, the basic properties for metals are only two in number: the Young's modulus E, which governs tensile stress and strain, and the shear modulus G, which governs shear stress and strain. Alternatively, instead of the shear modulus, Poisson's ratio v could be used. The fundamental starting point in examining the elastic properties of materials is Hooke's law, which relates stresses to strains. For the general case of a solid, there are six stress components ? (three tensile and three shear) and six strain components ? (also three tensile and three shear) that are related by the following compliance matrix equation:
| (E.1) |  |
[It should be kept in mind that although strains are quantities that can be measured, stresses are really mathematical abstractions (albeit good...
