The elastic moduli of isotropic materials

Because the simplified notation involves a matrix rather than a tensor it is necessary to convert back into tensor notation in order to calculate, for instance, a compliance in terms of a rotated set of coordinate axes, using the tensor relationship 

Most of the present book is concerned with isotropic polymers, for which measured properties, such as the Young s modulus E, Poisson s ratio v and the shear modulus G, relate directly to the constants of the compliance matrix. 

Thus we obtain the stress-strain relationships derived more simply in Section 

Another basic quantity is the bulk modulus K, which determines the dilation A = + Cyy + gzz produced by a uniform hydrostatic pressure. Using the stress- 

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