Brittle materials

The fragility is the ability of certain materials to fracture or breaks into smaller pieces, suffering little or no deformation. It is the opposite of toughness and is a property of substances whose response to stress or tension leads to the appearance of cracks inside.

The brittle materials thus have little or limited elasticity: are unable to recover its original shape after being subjected to a force exceeding its strength. Similarly, they are not very ductile, that is, they lack the ability to deform in the face of sustained effort over time.

However, brittleness and hardness should not be confused, since they refer to different properties: hardness has to do with the resistance of the surface of a material to deformations, while brittleness refers to its ability to fracture into small parts instead of to deform. 

Use of brittle materials

Since brittle materials are capable of absorbing a very limited amount of energy, they are not usually desirable when constructing or building durable objects, such as foundations or bridges. In fact, in these cases, brittleness is usually imposed by other materials, which in turn have indispensable specific properties, such as resistance to rust.

In other cases, on the other hand, brittleness is a desirable and predictable property, such as the case of emergency glass in a fire extinguisher box, which must be shattered with a relatively weak impact.

Examples of brittle materials

1. Diamond. The strongest known substance in the universe, diamond, is made of carbon atoms in such a tight arrangement that their bonds are almost unbreakable. However, the diamond can break, and then its enormous fragility is evident, as it breaks into smaller fragments and is impossible to deform.
2. Glass. One of the most verifiable examples of fragility in everyday life, it is enough to drop a glass vase on the ground to show its fracture into small pieces. This property allows it, along with its transparency, to be used in contexts where it may be necessary to break them in an emergency, such as fire extinguisher boxes or bus windshields.
3. Brick. One of the most used elements in construction is brick, a usually rectangular and hollow piece of fired clay, whose hardness and weight is comparable to its fragility. It is a very cooked (350 ° C) and very economical version of the adobe that ancient cultures used to make their homes.
4. Ceramic. Ceramic is called the art of making objects with earthenware, clay, clay, or other materials that, once fired, acquire hardness and fragility, and it is possible to paint and decorate. Examples of this are the ornamental or funerary vessels of ancient cultures, such as the Egyptian, or many ritual figures sculpted in this type of material as well.
5. Some polymers. Specifically, polymethylmethacrylate (PMMA), polystyrene (PMS), and lactic polyacid (PLA), among others, are organic substances usually derived from petroleum, built in the form of acrylic plates. They are usually resistant and transparent, but fragile.
6. The shell of the eggs. We have all had the disastrous experience of inadvertently breaking an egg, and we know that its shell is hard and firm but extremely fragile and that it takes just one hit to scratch and crack or tear it to bits. These shells are made of calcium crystals and other minerals bound together by a layer of protein.
7. Crystal. Crystals are forms of presentation of solid matter, whose molecules are arranged based on a specific, non-diffuse and well-defined pattern. They are formed from metamorphic processes of minerals, or from the solidification of gases (crystallization) or the evaporation of waters with high salt content. Crystals can be more or less resistant, but always fragile and not very elastic.
8. High carbon steels. Steel is the product of an alloy of iron and carbon, this metal being a ductile, resistant and tenacious, but vulnerable to corrosion. For this reason, it is alloyed with carbon and other materials to make it resistant to rust and to obtain steel; but in return, the presence of carbon at high levels makes it fragile, that is, it reduces its natural ductility and makes it brittle.
9. Porcelain. Porcelain is a white, compact, waterproof, hard, and fragile material that is very often used to make tableware, vases, lamps and ornamental objects, being more sophisticated than china or other clays, although just as fragile. It is made from quartz and other ground minerals, kaolin, feldspar, and everything is baked.
10. Whiteboard. Chalk or pastel is a fragile and powdery white clay, made in long sticks, a classic teaching instrument for writing on a blackboard. It is also used, pulverized, in the cleaning of some metals.
11. Dry plaster. This colorless calcium sulfate mineral is used, with an addition of water, to form a highly malleable plastic mass, ideal for construction or modeling work. By losing the water to the environment, the plaster proceeds to harden and become brittle, as it loses all its elasticity.
12. Graphite. Another of the natural presentations of carbon is this mineral made up of overlapping graphene layers. It is black, very soft and opaque, while fragile. In fact, it is used for pencil tips, which often tear into smaller pieces when we apply too much pressure or drop the pencil to the ground a lot.
13. Some woods. Although the specific properties of the wood vary according to the tree of its origin, some are more elastic than others and some much more fragile, easy to chip like balsa wood or wood in an advanced state of decomposition.
14. Tin rich bronzes. Bronze is the result of the alloy between copper and tin, and it is a very precious material for its ductility and malleability, but when having large amounts of tin in its constitution, it loses this property and becomes a brittle metal, easily splintered.
15. Alkali metals. Like sodium (Na), calcium (Ca), magnesium (Mg), and others, which in their solid-state become so desiccated that they obtain enormous hardness and also a lot of brittleness.