Industrial Engineering

Understanding Brittleness of materials

When under stress, a material is said to be brittle if it cracks with little elastic deformation and little or no plastic deformation. Even materials with high strengths that are brittle tend to absorb relatively little energy before breaking. A loud snapping sound is frequently present when something breaks.

It is typically used for materials that fail when there is little to no plastic deformation prior to failure when it is utilized in materials research. The fractured pieces should fit perfectly together as there hasn’t been any plastic deformation, which is one way to verify this.

Brittleness of a material

In this article, you’ll get the following questions will be discussed:

  • What is brittleness?
  • Brittleness in different materials
  • How do materials change to brittle?
  • What is the effect of pressure on brittleness?

 

Read more: Different types of material mechanical properties

What is brittleness?

The term “brittleness” refers to a material’s tendency to fracture under stress but to only slightly deform before to doing so. High compressive strength and low tensile strength are characteristics of brittle materials, as are little deformation, poor resistance to impact and vibration of load, and high compressive strength. The majority of non-metallic inorganic materials are fragile.

When under stress, a material is said to be brittle if it cracks with little elastic deformation and little or no plastic deformation. Even materials with high strengths that are brittle tend to absorb relatively little energy before breaking. A loud snapping sound is frequently present when something breaks.

It is typically used for materials that fail when there is little to no plastic deformation prior to failure when it is utilized in materials research. The fractured pieces should fit perfectly together as there hasn’t been any plastic deformation, which is one way to verify this.

Below a threshold temperature known as the glass transition temperature (Tg) or the ductile to brittle transition temperature (DBTT), metals and polymers become brittle. Particularly when forces are exerting themselves on the body, this fast change is disastrous. It is observed that the fracture growth is orthogonal to the applied forces that pass through molecular grains or grain borders.

In this case, the temperature affects a material’s molecular structure in a way that prevents it from maintaining its flexibility, which results in material failure. In general, all materials will eventually fail when their limits are exceeded, however, brittleness refers to a material’s tendency to fail before it changes in shape or size.

Failure of brittle materials happens under two circumstances: stress acting on the material’s surface and ambient temperatures below the material’s melting point.

Read more: Understanding Hardness, strength, and toughness of materials

Brittleness in different materials

The followings are materials with their level of brittleness:

Polymers

Polymer mechanical properties are susceptible to fluctuations in temperature close to room temperature. For instance, poly (methyl methacrylate) is exceedingly brittle at 4 °C but becomes more ductile as the temperature rises.

Amorphous polymers are those that respond differentially to temperature changes. At low temperatures, they may behave like glass (the glassy zone), at intermediate temperatures, they may behave like a rubbery solid (the leathery or glass transition region), and at higher temperatures, they may behave like a viscous liquid (the rubbery flow and viscous flow region).

Viscoelastic behavior is the name given to this action. The amorphous polymer will be hard and brittle in the glassy zone. The polymer will become less brittle as the temperature rises.

Read more: Raw materials used in making Iron and steel

Metals

Due to their slip systems, some metals exhibit brittle qualities. Metal is less brittle the more slip systems it has because several of these slip systems can undergo plastic deformation. On the other hand, the metal will be more brittle with fewer slip systems since less plastic deformation may take place. For instance, HCP (hexagonal close-packed) metals are often brittle and have few active slip systems.

Ceramics

Due to the difficulty of dislocation motion or slip, ceramics are typically brittle. Crystalline ceramics have a limited number of slip systems, which makes deformation challenging and increases the ceramic’s brittleness.

Ionic bonding is typically present in ceramic materials. Slip is further limited as a result of the ions’ electric charge and their attraction to other ions with similar charges.

Read more: Understanding powder metallurgy

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How do materials change to brittle?

Through toughening, materials can be made more brittle or less brittle. A material typically has two options when it reaches the limit of its strength: deformation or fracture. By preventing the mechanisms of plastic deformation, a naturally pliable metal can be made stronger, but if this is done to an extreme, fracture becomes the more likely result and the material can become brittle. Therefore, increasing material toughness requires careful balancing.

Glass and other naturally fragile materials can be efficiently toughened. The majority of these methods use one of two mechanisms: either to deflect or absorb the fracture tip as it spreads or to generate precisely regulated residual stresses that will drive cracks from specific known sources to shut.

Laminated glass, which consists of two sheets of glass separated by a polyvinyl butyral interlayer, uses the first principle. As a viscoelastic polymer, polyvinyl butyral absorbs the expanding crack. Toughened glass and pre-stressed concrete both employ the second technique.

Prince Rupert’s Drop offers an illustration of glass toughening. High-impact polystyrene, also known as HIPS, is a good illustration of how brittle polymers may be made tougher by incorporating metal particles to cause crazes when a sample is pressured. Silicon carbide and transformation-toughened zirconia are the least fragile structural ceramics.

Composite materials, where brittle glass fibers, for instance, are incorporated in a ductile matrix-like polyester resin, employ a distinct philosophy. At the glass–matrix interface, cracks emerge under tension, but there are so many of them that a lot of energy is absorbed, making the material more durable. Metal matrix composites are made using the same basic idea.

Read more: Different types of furnaces 

What is the effect of pressure on brittleness?

In general, pressure can be used to raise a material’s brittle strength. This occurs, for instance, in the brittle-ductile transition zone at a depth of about 10 kilometers (6.2 mi) in the Earth’s crust, where rock is more likely to bend ductilely and less prone to fracture.

FAQs

What are brittleness and its example?

After being strained beyond their elastic limit, brittle materials almost rapidly start to fail toward fracture or rupture because they have a tiny plastic zone. Brittle materials include things like bone, cast iron, porcelain, and concrete.

Read more: Understanding iron ore smelting process

What are ductility and brittleness?

While brittleness refers to a material’s propensity to fracture or break rather than bend plastically under tensile pressure, ductility refers to a solid material’s capacity to do so.

What are the types of brittleness?

Transgranular and intergranular fractures are the two main forms of brittle fractures.

Is Brittleness a metal property?

Ceramics, glass, and cold metals often make up the majority of brittle materials. Metal brittleness aids in identifying the threshold cooling temperature at which a ductile material becomes brittle.

What is a brittle material?

Glass, ceramic, graphite, and some alloys with very low plasticity are examples of brittle materials. In these materials, cracks can start without plastic deformation and quickly progress to brittle breakage.

Read more: Understanding the common types of metal, their properties & uses

In summary

Brittleness is an essential property to be considered when selecting materials for a project. It refers to a material’s tendency to fracture under stress but to only slightly deform before to doing so. High compressive strength and low tensile strength are characteristics of brittle materials, as are little deformation, poor resistance to impact and vibration of load, and high compressive strength.

That is all for this article, where the answers to the following questions are provided:

  • What is brittleness?
  • Brittleness in different materials
  • How do materials change to brittle?
  • What is the effect of pressure on brittleness?

I hope you learn a lot from the reading, if so, kindly share with others. Thanks for reading, see you around!