The property of having identical mechanical behaviour regardless of the direction of loading or measurement.
An isotropic material has only two independent elastic constants: E and ν (the shear modulus G = E/2(1+ν) follows). In practice, perfect isotropy is an idealisation: even rolled sheet metal has mild texture. Cast metals and amorphous polymers approximate isotropy. For isotropic materials, stress-strain relationships are fully described by the generalised Hooke's law using E and ν.
Isotropic material models are valid for injection-moulded thermoplastics, cast metals, and some SLA/SLS 3D prints. Using isotropic models for FDM parts overestimates Z-direction properties. MJF (Multi Jet Fusion) and SLS powder-bed parts are nearly isotropic due to three-dimensional powder bonding: a key advantage over FDM for structural applications.
Assuming isotropy for FDM parts in FEA is a common and serious error: it typically overestimates Z-direction stiffness by 30-50% and strength by 50-100%. SLS and MJF parts are isotropic in a statistical sense but still have some surface-core property gradient. Always validate isotropy assumptions with mechanical testing in multiple orientations.
Related terms: Anisotropy, Young's Modulus, Poisson's Ratio
| Field | mechanics, engineering |
|---|---|
| Also called | Isotropic Material |
Engineer, author of The Big Book of 3D Printing and additive manufacturing expert