# Difference Between Isotropic and Orthotropic

## Main Difference – Isotropic vs Orthotropic

All materials have chemical and physical properties. Physical properties can be either mechanical properties or thermal properties. Materials can be categorized as isotropic, anisotropic or orthotropic based on the measured values for mechanical and thermal properties. The main difference between isotropic and orthotropic is that isotropic means having uniform mechanical and thermal properties in every direction whereas orthotropic means not having uniform mechanical and thermal properties in every direction.

### Key Areas Covered

1. What is Isotropic
– Definition, Properties, Examples
2. What is Orthotropic
– Definition, Properties,  Examples
3. What is the Difference Between Isotropic and Orthotropic
– Comparison of Key Differences

Key Terms: Anisotropic, Axes of Symmetry, Glass, Isotropic, Material, Metal, Orthotropic, Transversely Isotropic

## What is Isotropic

Isotropic refers to a particular substance having uniform mechanical and thermal properties in every direction. In other words, isotropic materials have the same values for thermal and mechanical properties in all direction. Isotropic materials have an infinite number of planes of symmetry.

A material becomes isotropic when there is a high degree of chemical bonding. For example, glass and metals are isotropic materials. In a metal, there are many atoms sharing electrons in different directions, and the chemical bonding is non-directional. Therefore, the mechanical and thermal properties are similar in every direction. This makes it isotropic.

Figure 1: Glass is an Isotropic Material

A mixture of gases is isotropic. This is because if heat is applied to that gas mixture, that heat will spread everywhere in that gas and the temperature of that gas mixture would be the same at every point of that mixture.

Isotropic material can be either homogeneous or non-homogeneous. For example, glass (in the above image) and steel are non-homogenous material but are isotropic. When a uniform pressure is applied to steel, every point will deform in equal amounts.

## What is Orthotropic

Orthotropic refers to not having uniform mechanical and thermal properties in every direction. Orthotropic materials have different values for the same property when measured in different directions. If a material is orthotropic, then it has mechanical and thermal properties that are unique and independent of that direction.

This term is defined for the three main directions that are used to give the dimensions of a material. These are perpendicular to each other ex: longitudinal, radial, and tangential directions. Therefore, orthotropic materials have three axes of symmetry.

Figure 2: Three Axes of Symmetry for a Log of Wood

Orthotropic materials show values for properties at a particular point in an object rather than the whole object. But if the object is homogenous, the values measured can be the same. Transversely isotropic materials are orthotropic materials that have only one axis of symmetry.

## Difference Between Isotropic and Orthotropic

### Definition

Isotropic: Isotropic refers to a particular substance having uniform mechanical and thermal properties in every direction.

Orthotropic:  Orthotropic refers to not having uniform mechanical and thermal properties in every direction.

### Axes of Symmetry

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

Orthotropic:  Orthotropic materials have three axes of symmetry.

### Examples

Isotropic: Isotropic properties can be observed in metal, glass, etc.

Orthotropic: Orthotropic properties can be observed in wood, some crystals, rolled materials, etc.

### Conclusion

Materials can be named as either isotropic or orthotropic based on the values measured for their physical properties. The main difference between isotropic and orthotropic is that isotropic means having uniform physical properties in every direction whereas orthotropic means not having uniform physical properties in every direction.

##### References:

1. “Isotropy: Definition & Materials.” Study.com, Available here.
2. “Isotropic and Orthotropic Materials.” 2012 SOLIDWORKS Help – Isotropic and Orthotropic Materials, Available here.
3. “Orthotropic material.” Wikipedia, Wikimedia Foundation, 26 Aug. 2017, Available here.

##### Image Courtesy:

1. “1476905” (Public Domain) via Pixabay
2. “Wood growth ill” (CC BY 2.5) via Commons Wikimedia