What is Flexibility?
The ability of a material to deform elastically and return to its original shape after stress is removed.
Flexible materials can be stretched reversibly when they undergo elastic strain. The yield strength, or maximum stress that a material can withstand before breaking or permanently deforming, is the material property that characterizes the elastic limit.
Beyond thickness, the flexibility of materials can be compared using the yield strength to elastic modulus ratio, which reflects how strong or weak a material is.
Why Are Flexible Materials Important?
Flexibility is important because it allows parts or tools to give way when force is applied to them or when they collide with something. As a result, these parts or tools can perform tasks that require a light touch.
Common Applications for Flexible Materials
Flexible materials are commonly used to 3D print the following applications:
- Bumpers. “Bumpers” made of flexible materials can push glass or other breakable materials to the side without breaking them. In its bottling plant in Seville, Spain, Heineken uses flexible materials for this purpose.
- Joint sealing Sealing joints made of flexible materials can be used in all industries that use or process liquids or oils in their factories because of their ability to deform to the right geometry and allow for a tight fit.
- Grippers. Some companies make grippers out of flexible materials that allow for gentle product handling.
What Are the Various Types of Flexibility?
In everyday life, there are two types of flexibility: elasticity and plasticity. These two types of flexibility may appear to be quite similar on the surface, but once you understand how they work, they become something quite different and distinct from one another. When we reduce it to its most basic form, we can divide the ways that materials bend into two distinct categories and forms of change:
Elasticity means that materials can change their shape when a force is applied and will return to their original shape after this force is removed. Rubber is a good example of how this works- when you stop stretching a rubber band, it goes back to its original shape. Although the particles and their bonds between them are distorted when the force is applied, the internal structure of the material can return to its original form.
Plasticity means that materials can change their shape when a force is applied to them, but they do not return to their original shape when the force is removed and will require external force to bend them back into their original shape. Think about paperclips – we can bend and twist them into new shapes, and they hold these shapes until we bend them again. Although the internal structure remains a single unit, it’s permanently changed, some internal bonds may have been broken, and it won’t easily return to the exact structure that existed before the force was applied.
This is why even flexible materials can break: if the force applied to the material is too strong, the bonds between the particles can be damaged to the point where they completely split, and the material breaks.
When we bend the paperclip, the bonds between the latticed metal particles stretch and, if under too much tension, snap. Even the most elastic materials have a limit to how far they can be stretched before breaking.
All materials are elastic and plastic up to a certain point – and it’s important for people to understand how much so when they’re trying to make something – a building needs materials with a certain amount of elasticity so that if it’s hit by something, it can absorb some of the impacts without breaking, and plasticity to make sure that if the impact is beyond what the material can absorb without bending, that it bends more than breaking entirely.
What is the Difference Between Elasticity and Flexibility?
Elasticity and flexibility are two distinct concepts and properties. Rubbers, for example, are primarily elastic and flexible (ductile) materials at room temperature, whereas glass is also elastic but rigid (brittle). The flexibility of a material is a property related to its toughness (which is resistance to impact loading), not its elasticity.
As a result, elastic materials can be either extremely tough (ductile) or extremely brittle.
We can define elasticity as a material’s resistance to permanent deformation (against plastic deformation), whereas ductility (flexibility) is related to the amount of energy that a material can absorb during deformation. Glass is stiffer and more elastic than rubber, but it breaks with far less force. Rubber is tougher than glass but softer.