Difference Between Isotropic and Orthotropic

Key Difference – Isotropic vs Orthotropic
 

In material science, both the terms “isotropic” and “orthotropic” are related to mechanical and thermal properties along the three directions, but there exists a distinct difference between these two terms. The key difference between isotropic and orthotropic materials is that isotropic means having the same value for mechanical and thermal properties in all directions, and orthotropic means not having the same value in all directions.

What are Isotropic Materials?

The meaning of “isotropy” is uniform in all direction; this term is derived from two Greek words “isos” (equal) and “tropos” (way). This term is used in many areas, and its meaning slightly changes depending on the subject area. Mechanical properties of isotropic materials do not depend on the direction; in other words they possess identical values in all directions. Glass and metals are two examples of isotropic materials.

The microscopic structure of isotropic materials can be homogeneous or non-homogeneous; steel is isotropic, but its microscopic structure is non-homogenous.

Examples of isotropic material properties:

• Density
• Modulus of Elasticity
• Thermal coefficient of expansion
• Poisson’s Ratio
• Shear Modulus of Elasticity
• Damping
• Yield Strength
  

  3D representation of a liquid crystal in the isotropic state

What are Orthotropic Materials?

Orthotropic materials have different material properties along three perpendicular axes (axial, radial and circumferential). In general, these materials are orthotropic and inhomogeneous. The most common example for an orthotropic material is wood.

What is the difference between Isotropic and Orthotropic?

Definition of Isotropic and Orthotropic

Isotropic Materials: A material is said to be isotropic if its mechanical and thermal properties are same in all direction.

Orthotropic Materials: A materials are said to be orthotropic if its mechanical and thermal properties vary and independent in all three directions.

Characteristics of  Isotropic and Orthotropic

Properties

Isotropic Materials: Isotropic materials have a unique value for material properties such as density, modulus of elasticity, the thermal coefficient of expansion, Poisson’s ratio, damping, yield strength, etc.

Orthotropic Materials: Orthotropic materials do not have a unique value for the material properties throughout the material.

Microscopic Structure

Isotropic Materials: Isotropic materials can be either homogeneous or non-homogeneous.

Orthotropic Materials: As a whole, orthotropic materials are inhomogeneous.

Plane of Symmetry

Isotropic Materials: Isotropic materials have an infinite number of planes of symmetry.

Orthotropic Materials: Orthotropic materials have three planes (or axes) of symmetry.

Examples of Isotropic and Orthotropic Materials

Isotropic Materials: Glass, metals

Orthotropic Materials: Wood, many crystals and rolled materials.

 

Image Courtesy:

“Isotropic3d” by Stille – Own work. (CC BY-SA 3.0) via Wikimedia Commons

“Taxus wood” by MPF – copied from en.wikipedia 17:13, 5 November 2004 . . MPF . . 421×427 (38110 bytes)Original source: Photo: MPF. (CC BY-SA 3.0) via Commons