10 Examples of Composite Materials

The composite materials are those that are made up of two or more different elements or substances, the combination of which gives the resulting matter the joint characteristics of its components, that is, those of the two original substances at the same time. For example: adobe, concrete, bone.

This allows a specific selection of components to obtain materials endowed with unusual characteristics in terms of rigidity, lightness, resistance, conduction of electricity, resistance to corrosion, etc.

Most composites are artificially created by man. However, some may appear in nature, the product of the evolution of living beings and in many cases they are binding materials that benefit from the chemical interaction of their components.

In general, composite materials are characterized by:

  • Consist of two or more physically distinguishable and mechanically separable components.
  • Have several chemically different phases, insoluble among themselves and separated by an intermediate phase or interface.
  • Possess high synergy, that is, its mechanical properties are superior to the simple sum of those of its separate components.
  • Distinguish from polyphase materials, such as metal alloys, in which it is possible to alter the phases present through thermal variation (heat).
  • Possess a reinforcing agent (fundamental in the constitution of the mechanical properties of the material) and a matrix (continuous phase that defines the physical and chemical properties of the material).

Types of composite materials

The following types of composite materials can be identified:

  • Particle Reinforcement Composites. In a softer and more ductile matrix, components of a hard and brittle material are discretely and uniformly dispersed.
  • Dispersion-hardened composites. They present reinforcing particles of very minute sizes, dispersed in the base matrix.
  • Fiber-reinforced composite materials. They usually contain tensile resistant fibers in a matrix usually made of resin that envelops the fibers, transfers the load from the broken fibers to the intact ones and gains strength.
  • Structural composite materials. They are made up of both simple and composite materials, usually laminar (sandwich) such as those used in construction, to combine the properties of both materials in the same wall.

Examples of composite materials

  1. Cermet. It is a conjunction of ceramic and metal, designed to withstand high temperatures and abrasion (like ceramics) but enjoy the malleability of metals. Usually the matrix of these materials is metal (nickel, molybdenum, cobalt) and the reinforcing phase is formed by refractory carbides, oxides, albumin and borides, typical of ceramics. This allows the manufacture of cutting tools that combine hardness with the property of being stainless (and have a long useful life), especially the new developments based on titanium and cobalt.
  2. Nacre. It is an example of a composite material of natural origin, without the intervention of man. It is a hard, white organic-inorganic substance with iridescent reflections, which forms the inner layer of the shell of many mollusks, such as mother-of-pearl. Mollusks can secrete this mixture of calcium carbonate and biopolymers to repair their shells or to encompass impurities or microbial agents that penetrate it, thus giving rise to pearls.
  3. Plywood. Also called multilaminate, plywood, plywood or plywood, it is a board of thin sheets of wood glued to each other with their fibers in transverse orientation, with synthetic resins, pressure and heat. It is coated with sulfuric acid after processing to be odorless, containing polymers and benzenes, and is particularly useful in construction.
  4. Adobe. They are uncooked bricks, that is, fillings for construction, made of clay and sand or other masses of mud, mixed with straw and dried in the sun. They have been used since ancient times to make walls and rudimentary constructions, usually in the form of bricks (rectangular). Despite being an excellent thermal insulator, adobe absorbs a lot of moisture by capillarity and loses its hardness, so it must be installed on a water-repellent stone or concrete base.
  5. Concrete. Also called “concrete”, it is the composite material most used in construction at the same time, it is a combination of various substances: cement, sand, gravel or gravel and water. With this combination, a homogeneous mixture is obtained that in a few hours sets and hardens to a stony consistency. Most civil engineering works involve the use of concrete.
  6. Oriented Strand Board. Called OSB (Oriented Strand Board in English), they are a type of conglomerate boards, an evolution of plywood, since instead of joining several sheets of wood, they are made with several layers of shavings or wood chips all oriented in the same direction. A homogeneous material is thus obtained from phenolic or polyurethane resins, formaldehyde or melamine. Often, other additives are also incorporated to improve resistance to fire, humidity or to repel insects.
  7. Pykrete. This composite material is made with 14% sawdust or some other organic wood pulp, in an 86% ice matrix. Its name comes from its inventor, Geoffrey Pyke, who proposed it to the Royal British Navy to make hard-to-sink aircraft carriers. Pykrete has hardness close to concrete, low melt index and enormous resistance to tensions.
  8. Glass reinforced plastic. Known as GFRP (Glass-Fiber Reinforced Plastic in English), is a composite material formed by a plastic or resin matrix, reinforced with glass fibers. The result is a lightweight, strong, easy-to-mold material, often popularly called “fiberglass”. It is widely used in the manufacture of parts, in the nautical and telecommunications industry, as well as in the construction sector.
  9. Asphalt concrete. Very used in the paving of roads or highways, it consists of a mixture of asphalt and mineral aggregates of various kinds, to obtain a uniform and bituminous paste that, when applied hot, hardens and waterproofs, and constitutes an ideal material for urban public works .
  10. Bone. It is a composite material that occurs in nature. Bones are made up of a bone matrix reinforced by collagen fibers, a protein that gives it its natural flexibility and also contains calcium phosphate, which helps maintain the strength of the bone structure. This results in a hard, brittle, resistant compound, flexible to some extent, but lightweight.