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Carbon is an expensive but very versatile material that can withstand high loads and is therefore not only used in industry, but increasingly in the hobby sector as well. However, there are a few things to consider when bonding carbon, which we will explain to you below. We will also explain how to use certain adhesives for carbon bonding.
Table of Contents
What Is Carbon (CFRP)?
Carbon is also known as carbon fiber reinforced polymer (CFRP). It is a composite material made of carbon fibers with a plastic matrix that fills the spaces and bonds the fibers together. This combination creates a material that is expensive but extremely versatile, lightweight and incredibly strong, and can be used for a wide variety of projects.
As a rule, a resin, in particular epoxy resin, serves as the matrix. Various other thermoplastics and thermosets can also be used as the matrix. The resin gives the carbon its stability; the materials virtually interlock with each other and thus become particularly resistant to external influences. The fibers and matrix are laminated in both transverse and longitudinal directions to achieve the most durable and stable structure possible.
Carbon can be joined in various ways, but in principle, only bonding is advisable. This joining technique is not only less time-consuming than all other methods, it also does not lead to a weakening of the structure (as is the case with riveting or screwing, for example).
Applications for Carbon (Reinforced Plastic)
CFRP is used wherever materials are exposed to high loads. A high level of stiffness is required from the material. The many advantages of the material outweigh the disadvantage of its very high price.
Nowadays, carbon is used:
- As a progressive material in the automotive and aircraft industries;
- As a light and easily adaptable, but at the same time very stable, material in boat-building;
- As a material in wind turbines, especially in offshore operation;
- For road bikes to make them more stable and reduce their weight;
- For professional tennis rackets;
- In the hobby and crafts sector.
Important Points to Consider When Gluing Carbon Fiber
CFRP bonding presents some challenges to the user, but these are surmountable. You should pay attention to the following points:
- The carbon adhesive used must be low-shrinkage for CFRP bonding to succeed.
- The thickness of the adhesive layer should be as uniform as possible.
- Adhesives that ooze out must be avoided or removed immediately.
- The conditions under which the adhesive seam cures must be constant. For example, there must not be any high temperature or pressure differences.
- It is essential to pay attention to the thermal expansion behavior when bonding different materials, otherwise stresses will arise in the material that can lead to fractures or weakening.
- The curing temperature should be kept low, otherwise the outer shell could be subject to thermal damage.
Carbon Fiber Adhesive Recommendations
The best adhesive for carbon fiber can be found either in epoxy for carbon fiber or in carbon glue. We will discuss these two adhesive options in detail below, including the top-recommended product for each.
Epoxy for Carbon Fiber
An epoxy adhesive consists of two components that, once mixed, trigger a chemical reaction. A two-component epoxy-based adhesive forms extremely stable and durable bonds with a wide variety of materials. It also scores with many other advantages, which we will discuss below.
At this point, we recommend the Bob Smith Industries Quik-Cure two-component epoxy for bonding CFRP and carbon repair. This is an epoxy that will not only cure quickly, but it will form a durable yet flexible and lasting bond even in areas that tend to undergo high levels of vibration and stress. This product is not suitable for water immersion, but it is water-resistant to a degree, as it can be used on the interiors of wood-framed boats.
This epoxy can even be combined with micro-balloons in order to create a quick-curing putty. You need wait only one hour for the full durability of this epoxy to be realised, although your bonded items can be handled within just 15 minutes. This product offers a range of properties:
Due to its many advantages, we can absolutely recommend this two-component adhesive from Bob Smith Industries.
Areas of Application
In principle, a two-component epoxy resin-based adhesive is suitable for bonding all conceivable materials. Some plastics are an exception. The epoxy resin carbon adhesive is particularly suitable for very stable and durable joints that are exposed to high loads. For carbon repair, such as filling cracks and holes in the material, this two-component adhesive is the best choice.
Before bonding, the surface of both substrates must be roughened and thoroughly cleaned of dirt, dust, grease, and oil. Any wax must also be removed. Now, mix the components together on a disposable surface if the adhesive was not supplied in a double-chamber cartridge. Stir until the adhesive mass is cloudy, and then coat the substrates with the carbon adhesive. Make sure that the application is even, but not too thick.
The pot life of most epoxy adhesives is about five minutes. During this time, the two substrates must be joined at high pressure and fixed if necessary. After application, carefully close the cartridge or container. Now, you can store it for a long time without wasting the adhesive.
Superglue is the standard adhesive that every household should have. With its help, quick and easy repairs can be carried out, as it forms a stable bond with a wide variety of materials in the shortest possible time.
Our recommendation at this point is the Maxi Cure Insta-Set superglue combo pack by Bob Smith Industries. This superglue set includes a cyanoacrylate (CA) and accelerator, which when combined will form an immediate and super-strong bond.
This glue will bond to pretty much all surfaces, and can be applied in a variety of ways in order to achieve the strongest possible bond. This product can be used for bonding as well as gap-filling, and it can be carved, sanded, and feathered once dry to form a plastic-like finish.
The Bob Smith Industries superglue scores well with its many advantages and only one disadvantage. Thus, this product receives an absolute recommendation from us.
Areas of Application
Superglue is advisable for carbon fiber and many other materials whenever small, durable bonds need to be made. A little insider tip is the sealing of cut edges with the help of superglue. This not only seals them permanently, but also makes them absolutely water-resistant.
Such a seal is particularly advisable for CFRP cut edges to protect them from environmental influences. Simply apply the superglue to the cut edge with a fine dosing syringe and allow it to cure. Be careful not to apply the adhesive too thickly.
Superglue can be applied quite easily. As a rule, the tube is supplied with a very fine dosing syringe, with which the adhesive application is successful. The two substrates should be absolutely clean before application, i.e. free of grease, dust, and dirt. The adhesive is applied thinly and the two substrates are bonded together. Fixation is usually not necessary, as the superglue hardens very quickly.
Tips for Gluing Carbon Fiber
- For a better and more stable bond, you can heat the two surfaces to be bonded evenly. This better distributes subsequent loads over the bonded substrates.
- When repairing cracks, it is essential to pay attention to the manufacturer’s gap-bridging specification. This indicates the extent to which a crack or gap can be stably repaired.
If a hole is particularly large, it can be repaired by inserting new carbon layers. Before this, the old layers should be carefully ground off.
- Before applying the adhesive, the substrates must be thoroughly cleaned. They should be free of all potential soiling. This also applies to grease and oil residues.
- Cleaning can be carried out using organic solvents, or lukewarm water with added surfactants (soap). If you use a cloth for cleaning, it must be lint-free.
- After cleaning the gluing points, they should not be touched with bare hands, as otherwise the finger grease may deposit on them again. Use disposable gloves when gluing carbon fiber.
Prepare the Areas to Be Glued
- To achieve better adhesion, both substrate surfaces should be roughened. After this, of course, they must again be cleaned of the resulting grinding dust.
- After bonding, the substrates can be mechanically processed and painted without any problems.
Frequently Asked Questions
Can Objects Be Glued to Carbon?
The answer depends on the material of the object to be bonded. Basically, the answer is yes if, for example, the object is made of steel or another material that bonds well with CFRP.
CFRP is a very versatile and highly durable material that is relatively easy to bond. Pay attention to our tips for gluing carbon fiber, and then nothing can go wrong when working with it.