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Software Support for Introduction to Composite Materials Design-- 3rd Edition, CRC (2018) by Ever J. Barbero

## Micromechanics-Unidirectional-Intralaminar Poisson's ratio

There are two intralaminar Poisson's ratios, denoted (1,3) and (2,3). The (1,3) is assumed to be equal to the in-plane (1,2) Poisson's ratio because the material is transversely isotropic in the (2,3) cross section of the lamina. The in-plane Poisson's ratio (1,2) has his own page for calculation. The intralaminar Poisson's ratio (2,3) is calculated by CADEC using the periodic microstructure micromechanics method. Intralaminar means that Poisson's deformations are observed on a cross section of the composite plate or shell. In a lamina, the deformation occurs inside (intra) the lamina. In a laminate the deformation occur inside all of the laminas. Intralaminar deformation causes (or is caused by) intralaminar stress. Since this intralaminar stress can be calculated at the interface between laminas, and those interfaces are the weakest point of the laminate, the term interlaminar is often used, erroneously, to denote stresses, strains, and elastic properties associated with intralaminar deformations.