Composite materials: What are they and what are they for?

Composite materials have better strength, flexibility, toughness or lightness than many traditional materials.

A composite material comes from the union of several materials to generate another one with better properties. This is why they have multiple industrial applications. If you want to know what composite materials are, what they are used for, what are the different types that exist and their applications, read on.

What are composite materials?

A composite material is a combination of two materials that have different physical and chemical properties. Composite materials that are produced have better characteristics, for example, they may be stronger, lighter or electrically resistant, as they are often designed for a particular use that requires greater strength, efficiency or durability, among other characteristics.

The term composite refers more specifically to a structural material (such as plastic) within which a fibrous material (such as silicon carbide) is embedded.

Thanks to reverse engineering, we know that the remarkable properties of composite materials are achieved by inserting fibres of one substance into a matrix of another. While the structural value of a fibre bundle is low, the strength of the individual fibres can be harnessed if they are embedded in a matrix that acts as an adhesive, binding the fibres together and making the material strong.

Therefore, the constituent materials are not completely mixed and do not lose their individual identity, but are combined and contribute their most useful features to improve the final product.

In this sense, the constituent materials possess markedly different chemical or physical properties that merge to create a material with properties distinct from those of the individual elements. If we perform a chemical analysis of materials we can see how within the finished structure, the individual elements remain separate, which differentiates composite materials from mixtures and solid solutions.

The reason for their use over traditional materials is that they improve the properties of their base materials and are applicable in many situations.

Composite materials: examples

Some of the typical composite materials most commonly used in industry and engineering are as follows:

  • Reinforced concrete and masonry.
  • Composite wood, such as plywood.
  • Reinforced plastics, such as fibre-reinforced polymer or glass fibre.
  • Ceramic matrix composites (ceramic-metal composite matrices).
  • Metal matrix composites.

Types of composite materials

This type of material is made up of two components:

  1. The matrix, which shapes the part geometrically, gives cohesion to the material, is usually flexible and not very strong and transmits the stresses from one fibre to another.
  2. The reinforcement, which provides stiffness and strength to composite materials.

Therefore, we can classify composite materials according to either the type of matrix or the type of reinforcement.

Composite materials according to the type of matrix:

  • Metal matrix composites
  • Ceramic matrix composites
  • Organic, polymeric or reinforced plastic matrix composites. This group includes long fibre reinforced composites with a plastic matrix.

Organic matrices can be elastomers, thermosets or thermoplastics. In this aspect, thermosetting resins or matrices are the most commonly used to create high-performance composite materials. These resins produce a solid, insoluble and infusible product through a series of chemical reactions known as curing or cross-linking. Thermoplastics, on the other hand, melt when exposed to heat.

Composite materials according to reinforcements:

In terms of reinforcements, there are different types of reinforcements, such as carbon fibres, glass fibres, aramid fibres, natural fibres, etc.

Polymer matrix composites with fibre reinforcements are the most commonly used due to their light weight and excellent mechanical properties. These types of composite materials replace other traditional materials – mainly metallic – in those applications where the ratio of mechanical properties to weight has a decisive influence on the maintenance costs of the product.

The main fibres used as reinforcements are:

  • Glass fibres
  • Carbon fibres
  • Boron fibres
  • Ceramic fibres
  • Metallic fibres
  • Aramid fibres
  • Natural fibres such as sisal, hemp, flax, etc.

Regardless of the type of material they are made of, fibres may appear in the form of wicks, mats or fabrics.

Composite materials according to structure

On the other hand, composite materials can also be classified according to their structure as follows:

  • Sandwich structures: composed of a core and layers. They allow for improved mechanical properties, but without an excessive increase in weight. They also improve thermal and acoustic insulation.
  • Monolithic structures: pieces with a complex geometry, formed by superimposed fabrics with particular orientations that allow specific characteristics to be obtained. This type of material is designed to support the heaviest structural loads.

What are composite materials used for?

Composite materials have been used by humans for thousands of years. In Mesopotamia, strips of wood were glued on top of each other at different angles to create plywood, the Egyptians made death masks from flax or papyrus soaked in gypsum. Later, materials began to be reinforced with straw to strengthen mud bricks, pottery and boats. And so on until the 20th century, when the breakthrough in composite materials came with the invention of fibreglass.

The demand for lighter and stronger materials in industry has been the main driving force behind the development of composite materials, as they are cheaper, lighter, stronger and more durable compared to ordinary materials. In addition, one of the main advantages of composites is that they offer great design flexibility.

In this regard, they also resist heat and corrosion well. This makes them ideal for use in products exposed to extreme environments, such as ships, chemical handling equipment and the aircraft industry. When considering aircraft, it is worth remembering that composite materials are less likely than metals (such as aluminium) to break under stress.

Other common applications are in buildings, bridges and structures, swimming pool panels, car bodies, shower cabins, bathtubs, tanks, imitation granite, marble sinks and countertops.

Similarly, they are also increasingly used in general automotive applications, including panels, frames, interior components and other vehicle parts.

In Infinitia Industrial Consulting we have a wide experience in materials working in different projects to obtain high added value composite products. Do you want to improve your industrial products? Contact our Forensic Engineering team to offer you the best solution.