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A comprehensive guide offering technical advice about carbon fibre strengthening materials and how to properly prepare and handle carbon fibre composites

Carbon fibre is a pivotal ingredient to any strengthening and rehabilitation project – whether we are working on an industrial building, sewage works, or even a transport bridge. There are many reasons why we use and trust carbon fibre strengthening materials – they are lightweight, flexible, about three times stronger than steel, boost tensile strength, and, quite frankly, a joy to work with. The industry calls carbon fibre a `wonder material` and it is easy to see why.

But with all of these pros comes a rather chunky con – composite strengthening with carbon fibre is easy to mess up! We will say though, carbon fibre composites are a worthy application to master, and as long as you do your research and pick a specialist contractor who is fully trained and well-versed in the language of carbon fibre – you are on to a winning strengthening solution. In this comprehensive guide, we detail the `dos and don’ts` of using carbon fibre strengthening materials. We hope you find it useful, and if you have got any questions at any point, give us a call.

What are carbon fibre strengthening materials?

Carbon fibre strengthening materials are composites made from, and reinforced with, carbon fibre. Generally speaking, carbon fibre within composite strengthening is used to strengthen existing concrete structures or repair damaged structures – like buildings, factories, sewage works, bridges, and marine or coastal assets.

Carbon fibre composite materials come in lots of forms, including:

  • Carbon fibre sheet
  • Carbon fibre cloth
  • Carbon fibre strips
  • Carbon fibre fabric
  • Carbon fibre tubes
  • Pre-peg carbon fibre

Link to blog – The Pros and Cons of Carbon Fibre Reinforced Polymer

The don’ts of using carbon fibre strengthening materials

Because composite strengthening is relatively new in the specialist construction world, there is little advice out there detailing what you need to do if you hit a problem whilst using carbon fibre strengthening materials or similar products. Now, it is worth noting that carbon fibre has an intricate and complicated manufacturing process that uses lots and lots of energy. This means that 1) carbon fibre products are costly and you will want to avoid wasting them wherever possible and 2) repairing carbon fibre products, such as carbon fibre composites, is a whole lot tougher than producing them in the first place. In this section, we detail common mistakes that rookies (and some professional contractors) make while using carbon fibre strengthening materials.

Carbon fibre composites & common mistakes

The elements of carbon fibre composite materials are mixed to create the `matrix` – some of the ingredients exist to bind, meanwhile, others have the role of reinforcing – creating the ultimate strengthening potion. There are four types of matrix material in the carbon fibre product sphere: polymer, metal, ceramic, and carbon. Which category of matrix material your specialist contractor uses entirely depends on the project at hand – but one thing is for sure… every solution needs to be prepared, handled, and applied diligently or else your contractor could be faced with a common but costly mistake – which in turn, will become your problem!

Mistakes you will not see our contractors making

  1. The two parts of epoxy resin within carbon fibre composite products need to be mixed using specific proportions – the measures should not be misjudged, otherwise, the solution is at risk of being spoiled.
  2. If the epoxy resin solution is left standing for too long, it can cure at an unpredictable rate. This is bad news if the solution is left in its container without applying it soon enough – and normally the solution will spoil and will either be unusable or ineffective.
  3. Applying too much pressure when fastening, or using the wrong fasteners, or adding too many fastening points when using carbon fibre composite materials can lead to crumbling and flaking over time.
  4. The use of carbon fibre strengthening materials without being properly equipped with PPE – this can lead to serious problems with your skin, eyes, and respiratory system (please continue reading for more on this subject).

What are hazards of carbon fibre strengthening materials?

If we could write this section in neon lights with arrows pointing from every direction, we would. Composite materials can be hazardous to health. The correct PPE (industrial gloves, apron, and goggles as a minimum) need to be worn and the materials have to be handled responsibly, or serious injury can occur to contractors or those coming in contact with the project. Though, they are not any more or less hazardous than other materials of their ilk.

Here is a non-exhaustive list of the hazards of carbon fibre materials:

  1. The hardening aspect of epoxy resin contains amine compounds – which are skin, eye, and respiratory irritants;
  2. Certain machine cured fibres can become airbourne and become trapped in the lungs and lung tissue;
  3. When epoxies are mixed, they exude a toxic gas called exotherm (which is usually controlled). If this heats up uncontrollably (in a container, for example) the gas can bubble over and it may be inhaled;
  4. Tiny carbon fibres can scratch off and penetrate the skin, so it is recommended to wash the hands with soap and water well;
  5. Some people experience sensitivity to elements of the solution which can lead to skin or respiratory suffering. The only way to avoid this is by using the correct PPE, which is industrial gloves, an apron, and goggles as a minimum barrier of protection.

The dos of using carbon fibre strengthening materials

The best way to ensure the proper preparation, handling, and application of carbon fibre composites is to hire an expert who will get it right the first time. Do your research on specialist contractors and do not rush into a decision until you have at least booked a site visit (at CCUK, we call ours a feasibility study.

Techniques you may see our contractors trying

  1. Applying an extra 10 degrees of heat to curing (hardening or drying) epoxy resin – which generally doubles the reaction rate and speeds up our composite strengthening completion time.
  2. Preparing the surfaces beforehand to eradicate debris and to aid with binding – for example, cleaning the surface or sanding it down;
  3. Cleaning up any joints before the solution cures;
  4. Clamping the surfaces together while the solution dries; this technique helps to squeeze air and excess solution out while ensuring everything cures properly.

For further information on composite strengthening and its benefits, visit our designated webpage.

Carbon fibre composites glossary

Curing: The hardening process of the epoxy resin (related to curing time – which is the length of time it takes the resin to harden and gain full strength)

Exotherm/Exothermic reaction: A compound that releases heat and replaces weak bonds with stronger ones

Gelation: Where the solution turns from liquid to a gel-like substance, before eventually stiffening.

Matrix: Binding materials used to `glue` the reinforcement materials together

Post-cure: Where the materials are cured for additional time, at a higher temperature

Book your FREE quote & site visit for carbon fibre strengthening today

If you would like to know more about the benefits of carbon fibre strengthening, book your FREE quote and site visit here. There is no obligation to go ahead with the project afterward – it is simply your opportunity to get to know the product and whether the solution is suitable.