Computation of equivalent engineering properties

Laminate Composites computes the following equivalent orthotropic engineering properties:

Property	Behavior	Components
Density
Young’s Modulus	Membrane	Ex, Ey
Young’s Modulus	Bending	Ebx, Eby
Poisson’s Ratio		νxy
Shear Modulus	Membrane	Gxy
Shear Modulus	Bending	Gbxy
Shear Modulus	Transverse Shear	Gxz, Gyz
Coefficient of Thermal Expansion	Membrane	αx, αy ,αxy
Thermal Conductivity	Membrane	Kx, Ky , Kxy

Equivalent properties are only available for symmetrical and balanced laminates.

In the case of a general laminate, one must question the validity of using these equivalent properties in a structural simulation. For example, would the predicted Ex give an accurate estimate of the first buckling load of a pinned-pinned straight bar?

To make an analogy, consider this figure which shows an imperfect setup for the determination of the Young’s modulus of an isotropic material. The setup is such that the load is not perfectly aligned with the long sides of the sample. This condition results in shearing of the sample, just like an unbalanced laminate shears when subjected to in-plane tension or compression. Moreover, the load is not aligned with the mid plane of the specimen and an eccentricity is present. As a result, just like an asymmetrical laminate, the specimen also bends. Offsetting the laminate changes its stiffness and the equivalent properties do not adequately account for the membrane and bending behaviors. You can remove the offset by setting the Reference Plane Location to Middle in the Laminate Properties group of the Laminate Modeler dialog box to display the equivalent properties for an offset symmetric laminate.

Calculating effective engineering properties for general laminates is equivalent to using the properties measured with such an imperfect tensile test setup. The usefulness of the measured properties depends on the magnitude of the imperfections, just like the usefulness of effective engineering properties for general laminates depends on the degree of imbalance and asymmetry presented by the laminate.

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Computation of equivalent engineering properties, Simcenter 3D 2021.1 Series

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