Learning topic
Basic Material Properties and Models
Homogeneous and heterogeneous, isotropic, anisotropic and orthotropic materials, plus linear and nonlinear material models.
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Every calculation equation relies on a particular material model. Before using it, we must understand which properties are assumed to be the same at different points and directions and how the material responds to loading.
Homogeneity and heterogeneity
A homogeneous model assumes the same properties at all points of the considered volume. In a heterogeneous material, properties vary spatially. Real microstructures are heterogeneous, but at a suitable engineering scale a material can often be represented by effective homogeneous properties.
Isotropy and anisotropy
An isotropic material model has the same mechanical properties in every direction. In an anisotropic material, properties depend on direction. Orthotropy is an important special case with three mutually perpendicular material symmetry directions; it is commonly used for wood and laminated composites.
Linearity and nonlinearity
In a linear-elastic model, stress and strain are linearly related within the model’s range of applicability. Nonlinear response may result from material behavior, large deformation, or other physical effects.
Why the model matters
Equations and constants derived for isotropic materials cannot be applied to anisotropic materials without verification. The model must match the material, scale, loading direction, and required accuracy.