What’s the best adhesive for bonding composite materials?

Bonding composite materials can be a challenging process. If you have been struggling with this too, you’re not alone.

Here at Forgeway, we are manufacturers of specialist adhesives. Companies in the manufacturing sector often ask us how they can bond their composite materials. Whilst it is never a simple answer, there is always at least one adhesive that will stand out above others as the best for bonding your composite materials.

This article will discuss what you need to consider before bonding composite materials. You’ll also learn what considerations you should take before choosing your adhesive.

By the end of the article, you will know how to choose the best adhesive for bonding your composite materials.

What do we mean by composite materials?

‘Composite materials’ is very much an umbrella term. However, in simple terms, it means a substrate that is made up of more than one material.

A typical example of a composite material is a sandwich panel. Sandwich panels have a core material (usually plastic but can be anything) with a different material on both sides; like a sandwich. These are very popular in the construction industry as they are a combination of materials which gives them added benefits or characteristics to suit the user’s specific need.

One specific example of sandwich panels is an aluminium composite material (ACM) which is typically used for cladding. Even though ACM panels are a controversial topic in the construction industry, they are still very common. The core is surrounded by aluminium sheets on both sides. 

Other common composite materials include glass-reinforced plastic (GRP) and carbon fibre.

We will be using ACM panels for our examples in this article to help explain what we mean.

Is it difficult to bond composite materials?

No, it isn’t any more or less difficult to bond composite materials than other materials.

You just need to take more into consideration when choosing an adhesive. Because there is more than one material to consider, you will need to consider the whole composite panel when choosing an adhesive rather than just the outer material.

This means if you were bonding ACM panels to a building, you would need to consider what material is used for the core. Because the panel is on the exterior of the building, it will experience massive variations in weather conditions. Some materials that would typically make up the core (polyethylene or insulation) can be prone to thermal expansion and contraction. 

ACM panels are a typical example of composite materials

When this is happening, you will need to choose an adhesive that is not only temperature and weather-resistant but can also cope with the movement. So in this situation, you will need an adhesive with increased flexibility.

In summary, it isn’t any more or less difficult to bond composite materials, there are more materials you need to consider though.

How can I bond composite materials?

Since composite materials are used to create structures, it logically follows that you would need a structural adhesive to bond composites. We suggest you read our article on structural adhesives to get a better idea of them.

In summary, there are four main structural adhesives:

However, choosing an adhesive for bonding composite materials is very similar to choosing an adhesive for standard substrates. There are two steps where you need to pay extra attention when choosing the right adhesive for bonding composites.

Determine the material surface you are bonding to

The first thing you need to consider is the material you are actually bonding to. So with the ACM panel, the outer material is aluminium. This is the material you will be applying the adhesive to. In this instance, the surface material isn’t a problem as most adhesives will create a strong bond to aluminium.

Establish if that material is difficult to bond

A surface can be difficult to bond if it has contamination or its surface energy is low. Low surface energy plastics are notoriously difficult to bond. Polypropylene is a type of low surface energy plastic that is very common in the automotive and commercial vehicle industry. 

composite panel on the side of a vehicle
Composite panel on a caravan

So when choosing an adhesive to bond composite materials, you must first consider what the surface material is. The adhesive you choose must be able to achieve a strong bond to that material, and in order to do that you may need to consider a cleaning or priming process

Decide what characteristics your adhesive needs

Once you have established the adhesive will bond to the surface, you then need to make sure that bond will last. At this stage, you need to consider factors like strength, flexibility, and weathering resistance. Of course, there are other factors you need to consider when choosing a suitable adhesive, but you just need to make the bond will last and is durable.

Which is the best glue for bonding composite materials?

As we have already pointed out, there isn’t just one glue that is best for bonding composite materials. There are so many different types of composite materials that it is impossible to say there is one ‘best’ glue. It depends entirely on your application and what you want from the glue.

MS polymer and methyl methacrylate adhesives are extremely versatile. They can bond to most surfaces and have very few drawbacks. At least one of these will give you what you need from an adhesive.

However, as adhesive specialists, we want to help you choose the glue that is best for you. We manufacture over 3000 tonnes of adhesives every year. We know that there are some adhesives which will be better suited for your composite material bonding situation than others.

But without knowing your exact situation, we cannot say which glue is best for you. If you want the help of one of our experts, you can reach out to us for help, and one of our team will be in touch.

However, you also might want to figure it out for yourself. The article on structural adhesives will help you determine which one might be best for you.

Or you can download the comparison chart of structural adhesives by clicking on the banner below.

comparison chart of structural adhesives