Material assembly: your ADDEV’s Guide

Material assembly consists of joining 2 materials together, in order to create a mechanical link. In this article we will detail the different techniques to help you determine which solution meets your needs.

What is a joint?

All materials can be joined, but the efficiency of the joining will depend on a large number of physical and chemical parameters. The choice of the joining process must therefore correspond to the constraints and needs of your specifications.

Here are the parameters to take into account:

• What materials are to be assembled (metal, plastic, composite, wood, glass…)
• Are there any treatments (pickling, plasma, primer)
• What is the surface roughness?
• What is the size, weight, density?
• What are the mechanical constraints (static, dynamic, shear, traction, peeling, cleavage)?
• What is the environment (temperature, UV, humidity, presence of solvents, chemicals)?
• What is the implementation of the assembly?

An assembly can be:

• Permanent (not removable)
• Dismountable
• Direct
• Indirect, through a 3rd material

The different assembly techniques

Mechanical assembly

There is an infinite number of mechanical assembly methods, here are the most known:

Examples of indirect mechanical assemblies

• Stapling
• Nailing
• Screwing
• Riveting

Examples of direct mechanical assemblies

• Irreversible elastic interlocking between 2 parts. Frequent assembly method in the plastics industry.
• Shrink fitting: assembly of 2 parts by reversible deformation, using controlled mechanical tolerances

Mechanical joints: disadvantages

Indirect mechanical assembly methods have the disadvantage of causing mechanical stresses in the materials and are sometimes synonymous with deterioration (drilling, deformations, cracks, etc.)

Assembly by welding or brazing

Welding and brazing are processes that join materials by fusion. These highly technical processes are commonly used to join metal structures.

Welding is an irreversible joining method that is particularly difficult to implement in the case of metals. Indeed, it can lead to the deterioration of mechanical properties if it is poorly controlled and often requires post-treatments.

Metals are not the only materials joined by welding: 

Thermoplastics are commonly assembled in this way, for example the sealing of plastic packaging.

Assembly by gluing

Bonding is a method of joining two materials using an adhesive mass.

Thanks to the technical progress made by the industry, it is now possible to assemble almost all materials by bonding, for structural or non-structural applications.

Adhesive film assembly

An adhesive film is a thin material on which an adhesive mass (a glue) is deposited. When this film is coated with glue on both sides, it can be used to permanently join two materials.

It is also possible to make removable joints, using:

• Velcro® double-sided adhesive tape
• Adhesive magnetic tape

Advantages of adhesives and tapes

In addition to their versatility, bonding methods that use adhesives have the advantage of not altering the core properties of the materials, which is not the case with welding and indirect mechanical bonding.

What type of assembly should I choose?

No assembly is impossible, as long as you choose the right process. Do you want to maintain the integrity of the materials to be joined? In this case, choose indirect joining methods such as gluing or the use of adhesives.

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