Orthotropic Lamina Hookes Law in Principal Material Coordinates

3 Orthotropic Lamina Hooke s Law in Principal Material Coordinates 

FIGURE 8.14 Representative volume element from a unidirectional lamina, (a) Micromechanics, representative heterogeneous element and (b) macromechanics, equivalent homogeneous orthotropic element. 

Alternatively, designating the coordinates directed along and perpendicular to the 

It is apparent from Equations 8.42 and 8.43 that four material elastic properties (compliance or stiffness) are needed to characterize the in-plane behavior of a linear elastic orthotropic lamina. It is convenient to define these material properties in terms of measured engineering constants (Young s moduli, El d Ej, shear modulus Glt, and Poisson s ratios u,lt and (Xtl). The longitudinal Young s 

The major Poisson s ratio Plt is obtained from the same tensile specimen by measuring transverse and longitudinal strains and taking their ratio, such that 

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