What Is

What is the Difference Between Orthotropic and Anisotropic

The key difference between orthotropic and anisotropic materials is that the orthotropic materials show similar results when similar stimuli are applied in only three mutually perpendicular directions whereas the anisotropic materials show different results when similar stimuli are applied in all possible directions.

All materials we know have chemical and physical properties. These physical properties can be either mechanical properties or thermal properties. And, depending on mechanical and thermal properties, we can categorize all materials into isotropic, orthotropic, and anisotropic materials. In this article, we are discussing orthotropic and anisotropic materials.

CONTENTS

1. Overview and Key Difference
2. What are Orthotropic Materials
3. What are Anisotropic Materials
4. Side by Side Comparison – Orthotropic vs Anisotropic in Tabular Form
5. Summary

What are Orthotropic Materials?

Orthotropic materials are substances that show similar results when similar stimuli are applied in only three mutually perpendicular directions. We mainly see this term in material science as a subgroup of anisotropic materials. This is because, in both these types of materials, the mechanical properties change in some direction when external stimulation is applied.

Wood is a common example of an orthotropic material. Wood has three mutually perpendicular directions at which the properties are different from each other. For example, it is very stiff along the grain, least stiff along the radial direction, and somewhat stiff at the circumferential direction. This is because most of the cellulose fibers are aligned that way along the grain of the wood.

Orthotropic materials are a subset of anisotropic materials. The properties of these materials depend on the direction in which they are measured. There are three planes or axes of symmetry in orthotropic materials. In contrast, isotropic materials have the same properties in every direction.

What are Anisotropic Materials?

Anisotropic materials are substances that show different results when similar stimuli are applied in all possible directions. Thus, this is the opposite of isotropy. We can define it as a difference when measured along different axes, considering the material’s physical or mechanical properties. A good example of an anisotropic material is light that comes through a polarizer.

When considering the features of anisotropic materials, the properties of these materials are direction-dependent, and the refractive index is more than one. Moreover, chemical bonding is uncertain, and light can pass through anisotropic materials, although the velocity of light through the material is different in different directions. In addition to the above, these materials appear in a light colour, and we can observe double refraction as well.

What is the Difference Between Orthotropic and Anisotropic?

We can classify all the materials we know into three groups as isotropic, orthotropic, and anisotropic materials. The key difference between orthotropic and anisotropic materials is that the orthotropic materials show similar results when similar stimuli are applied in only three mutually perpendicular directions whereas the anisotropic materials show different results when similar stimuli are applied in all possible directions.

Moreover, the refractive index of orthotropic material is less than one, but that of anisotropic material is higher than one.

The following infographic summarizes the differences between orthotropic and anisotropic materials in tabular form.

Summary – Orthotropic vs Anisotropic

Materials are in three major types depending on the mechanical and thermal properties as isotropic, orthotropic, and anisotropic materials. The key difference between orthotropic and anisotropic materials is that orthotropic materials show similar results when similar stimuli are applied in only three mutually perpendicular directions whereas anisotropic materials show different results when similar stimuli are applied in all possible directions.

Reference:

1. “Orthotropic Material.” Orthotropic Material – an Overview | ScienceDirect Topics, Available here.

2. “Definition of Anisotropy – Chemistry Dictionary.” ChemiCool, Available here.

Image Courtesy:

1. “Wood, logs, stack, wooden, lumber, cut, texture, material, brown, firewood” (CC0) via Pxfuel