The fragility is the ability of certain materials to fracture or break into smaller pieces, undergoing 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. For example: diamond, brick, crystal, graphite.
The brittle materialsThus, they have little or limited elasticity: they are incapable of recovering their original shape once subjected to a force that exceeds their resistance. Similarly, they are little ductile, that is, they lack the ability to deform in the face of a sustained effort over time.
However, they should not be confused brittleness and hardness, since they refer to different properties: hardness has to do with the resistance of a material‘s surface to deformation, while brittleness refers to its ability to fracture into small parts instead of deforming.
Use of brittle materials
Since brittle materials are capable of absorb a very limited amount of energy, are not usually desirable when building or constructing durable objects, such as foundations or bridges. In fact, in these cases the brittleness is usually imposed by other materials, endowed in turn with essential specific properties, such as resistance to rust.
In other cases, however, brittleness is a desirable and predictable property, such as the emergency glass of a fire extinguisher box, which must shatter with a relatively low impact.
Examples of brittle materials
- Diamond. The strongest known substance in the universe, diamond is built of carbon atoms in such a close arrangement that their bonds are nearly unbreakable. However, the diamond can break and then its enormous fragility is evident, as it breaks into smaller fragments and is impossible to deform.
- Glass. One of the most verifiable examples of fragility in everyday life, it is enough to drop a glass to the ground to show its fracture into small pieces. This property allows, together 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.
- Brick. One of the most used elements in construction is brick, a usually rectangular and hollow piece of baked clay, whose hardness and weight is comparable to its fragility. It is a highly cooked (350 °C) and very cheap version of the adobe used by ancient cultures to make their homes.
- Ceramics. Ceramics is the art of making objects with earthenware, mud, clay or other materials that once cooked, 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.
- some polymers. Specifically, polymethylmethacrylate (PMMA), polystyrene (PMS) and polylactic acid (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.
- the shell of the eggs. We have all had the disastrous experience of accidentally breaking an egg, and we know that its shell is hard and firm but extremely fragile, and that a blow is enough to score it and crack it or turn it into little pieces. These shells are made of crystals of calcium and other minerals bound together by a layer of protein.
- Glass. Crystals are presentation forms 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 water with a high saline content. The crystals can be more or less resistant, but always fragile and very little elastic.
- high carbon steels. Steel is the product of an alloy of iron and carbon, this metal being ductile, resistant and tenacious, but vulnerable to corrosion. That is why it is alloyed with carbon and other materials to make it resistant to rust and obtain steel; but in return the presence of carbon in high levels makes it brittle, that is, it reduces its natural ductility and makes it brittle.
- Porcelain. Porcelain is a white, compact, waterproof, hard and fragile material that is very often used to make crockery, vases, lamps and ornamental objects, being more sophisticated than earthenware or other clays, although just as fragile. It is made from quartz and other ground minerals, kaolin, feldspar and everything is baked.
- Whiteboard. Chalk or pastel is a white, brittle and powdery clay, made into long sticks, a classic teaching tool for writing on a blackboard.. It is also used, powdered, in the cleaning of some metals.
- dry plaster. This colorless calcium sulfate mineral is used, with the addition of water, to form a highly malleable plastic mass, ideal for construction or modeling work. By losing water to the environment, the plaster proceeds to harden and become brittle, since it loses all its elasticity.
- Graphite. Another of the natural presentations of carbon is this mineral made up of superimposed layers of graphene. It is black, very soft and opaque, as well as fragile. In fact, it is used for the tips of pencils, which often break into smaller pieces when we apply a lot of pressure or drop the pencil on the ground a lot.
- some woods. Although the specific properties of wood vary depending on the tree it comes from, some are more elastic than others and some are much more fragile, easy to splinter such as balsa wood or wood in an advanced state of decomposition.
- Tin rich bronzes. Bronze is the result of the alloy between copper and tin, and it is a highly prized material due to its ductility and malleability, but since it contains large amounts of tin in its constitution, it loses this property and becomes a brittle, easily chipped metal.
- Alkali metals. Like sodium (Na), calcium (Ca), magnesium (Mg) and others, which dry out so much in their solid state that they become extremely hard and also very brittle.