Introduction: Building a Low Cost and Simple Carbon Fibre Moulding

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About: As our name suggests, the principle of Easy Composites is to make a complex and challenging subject as straightforward and accessible as possible. We do this through careful product selection, rigorous testing…

Welcome to our new Instructable!

This project is the latest in our series of tutorials showing tried and tested composites methods and techniques which don't require specialist equipment or experience - making working with carbon fibre possible for everyone!

In this Instructable project we cover the simplest and lowest cost method for creating an original moulded carbon fibre (CFRP) component demonstrated with this half scale model of an Efficiency Racer - the ideal demonstration project for Schools, Universities, Greenpower teams and home-builders.

This mouldless construction method is much faster and comes with a far lower price tag than the traditional method of:

PATTERN - MOULD - MOULDING

The project has lots of advantages for prototypes and one-off components and it's possible to get really great results;

What you will learn:

  • Which materials and tools are needed
  • The best method for shaping the foam to match your design
  • How to stop resin from sticking to the foam
  • How to hand-laminate the resin and carbon fibre onto the foam former
  • How to apply a resin overcoat to improve the finish
  • How to flat and polish the surface

BUT this process isn't suitable if:

  • You are making multiple parts
  • You need to produce heavier components
  • If you need a high quality cosmetic appearance on your project

We hope you enjoy this Instructable and find it useful. We would love to know what you think and answer any questions you may have in the comments below and we'd love to see your results if you follow our process!

Supplies

For this Instructable we sourced most of our materials from Easy Composites, however lots of the items are readily available depending whether you are buying online or from your local supplier.

  • Foam for creating the former, a saw for cutting and shaping and glue to bond the foam together
  • Cardboard or similar to make your template and a marker pen
  • Carbon Fibre or Fibreglass Fabric Reinforcement
  • Epoxy Laminating Resin
  • Epoxy Coating Resin
  • Release Film and Spray Adhesive
  • Peel Ply
  • Abrasive Pads
  • Flash Tape
  • Sanding block / DA Sander / Electric Polisher
  • Composites shears
  • Water spray and microfibre cloth

You will also need to wear the following PPE:

  • Safety suit, work gloves, nitrile gloves (when using epoxy resins), mask and goggles*

The safety and technical datasheets for the products you use should advise on the Personal Protective Equipment you will need for each step.

Step 1: Safety Information

When working with carbon fibre and chemicals like epoxy resin, it's important to take appropriate safety precautions. Take the time to download and read the TDS (technical datasheets) and SDS (safety datasheets) for the products that you are using, not only will this keep you safe, it will also help you to get the most out of the materials.

Remember, if you're using different materials to the ones we're using in this guide, the handling and behaviour of the product may be considerably different.

General guidance when working with epoxy resin:

  • Always wear eye protection when measuring, mixing or laminating with epoxy resin
  • Always wear nitrile gloves (not latex)
  • Although epoxy resin is almost odourless and has no volatile solvents, always work in a well-ventilated area. If you can't work with adequate ventilation, wear a vapour mask.

General guidance when working with carbon fibre:

  • Wear protective gloves when demoulding carbon fibre parts, the edges can be very sharp
  • Always wear a respirator when cutting or sanding cured carbon fibre (just the same as you would when cutting/shaping wood)

Step 2: Preparing and Shaping the Foam

Beginning with the creation of a pattern or template for the part you would like to make, when you have this you can then source the correct amount of foam for the project.

We used expanded polystyrene (also known as 'bead board') which is widely available from DIY stores and is inexpensive. You could use an alternative like RTM Styrofoam (blue foam) or polyurethane foam, which is more conventionally used in composites pattern making, but we found the polystyrene more than adequate.

Remember that solvent-based resins, such polyester resin and body-filler, will dissolve polystyrene foam if they come into direct contact with it. We don't use any solvent-based resins in the project but this is an important consideration if you planned to use polyester resins or fillers.

The foam we used came in sheets, so to create the pattern we:

  • Cut the sheets down into suitable lengths
  • Bonded the sheets together to make a block using a foaming PU adhesive
  • Create cardboard templates of the top and side profile of the shape
  • Roughly shape the form using a hand saw to create the basic shape
  • Refine the shape either by hand using abrasive paper or a DA Sander with 120 grit pads
  • For the fine finishing of the shape - sand the former freehand and keep checking by eye to ensure accuracy - if a high level of accuracy is needed, create a template to guide you and keep checking the surface by hand to avoid high spots or rough spots
  • If you have used an power sander, finish the process by hand to assure a fine, smooth finish

Step 3: Applying the Release Film

Once you are happy with the shape you will need to apply a release film to prevent the resin from bonding to the foam. It's really important to use a release film as traditional release agents like wax or PVA won't work on the open texture of a foam like polystyrene and would still allow the resin to mechanically bond to it, making it difficult to remove.

Wrapping the foam with release film will also make the release from the polystyrene much better.

The release film is bonded to the foam block using a conventional tacky spray adhesive such as 3M Super 77 or other spray adhesives (just check the suitability of the adhesive and the polystyrene foam).

The film is then applied to the foam block and smoothed out as it is applied. Small creases are not an issue as they will not be seen on the finished part. The shape may need several pieces of film and they are applied in the same way and overlapped and taped using Flash Release Tape to cover the block completely.

Step 4: Adding the Peel Ply

With the former wrapped in release film you are now ready to measure out the peel ply and carbon fibre reinforcement.

  • Measure and cut-out the peel-ply to cover the whole former
  • Cut out the fabrics using sharp household scissors or if you plan to work with carbon fibre regularly a pair of composites shears
  • Use the peel ply cut outs as a template to cut out the carbon fibre* reinforcement
  • Aim for 1mm thickness overall - so with our material this required 3 layers of material
  • Our project shape required the process to be split into a top and a bottom half - depending on the shape you are laminating you may be able to do it in one go

*If you've never handled carbon fibre fabric before you will need to treat it with great care, it is very delicate and can distort and fray


Next, accurately measure and thoroughly mix up a quantity of hand laminating resin (according to the manufacturers instructions) to attach the peel ply and in turn the carbon fibre. Always ensure that you double-pot the resin to avoid unmixed resin getting on to the project.

As a rule of thumb, the amount of resin needed in hand layup is approximately the same as the weight of the fabric reinforcement:

  • Brush apply a layer of resin on to the former
  • Drape the peel ply over the resin and then wet out the layer using the brush to drive the resin up through the fabric

Step 5: Laminating the Reinforcement

Now that the peel ply had been wetted out, the layers of carbon fibre can be applied and wetted out one layer at a time.

Repeating the process with each layer or 'ply'. Take special care working the resin into the fibre of the fabric and if needed use flat spreaders, squeegees or a finned rollers to spread the resin. The aim is to wet out the fibres fully but without leaving an excessive wet film or causing the resin to pool on the surface.

Once the layers of reinforcement have been applied, the edges of the fabric can be trimmed off to neaten the edges. The laminate is then left to fully cure according to the manufacturers instructions.

If like in our project, you will need to prepare for the second half of the layup, the edges of the carbon are de-nibbed and keyed up using 120 grit sandpaper and cleaned up before completing the 2nd half of the lay-up.

Repeat the process for the top half of the lay up and once complete leave to fully cure.

Step 6: De-Nibbing the Reinforcement and Keying the Surface

Now that the whole part has fully cured, remove any high spots and give the surface a good overall key in preperation.

  • Using a 120 grit paper, de-nib and key the surface of the part.
  • The purpose is not to sand into the carbon but only to remove high spots and give the whole surface an overall key ready for the resin coating

It is possible to do this by hand or with an orbital sander although some corners and areas of detail may still need hand sanding to get an even finish. Once the surface has been fully sanded, the part should be wiped down to remove any dust or debris.

Step 7: Applying the Surface Coating Resin

It is now time to move on to applying the coating resin to the part to provide the surface layer that can be flatted and polished to provide an excellent clear gloss finish. It's expected that there might be some waves and ripples in the part - this is perfectly normal due to the drape of the material and common in the open lay up process.

To make it possible to flat the surface out and leave the part with a great surface finish you will need to apply a clear surface coat using the following steps:

  • Accurately measure out and thoroughly mix up a suitable epoxy coating resin*
  • Typically you will need 300-500g of resin per square metre
  • Brush apply a coating of the resin - applying it at a thickness that won't run-off or flow excessively
  • Once the coating is fully applied leave it to partially cure to the B-stage**

*Always ensure that you double-pot the resin to avoid unmixed resin getting on to the project.

**The B stage is when the resin has firmed up but is still tacky, this is the ideal stage to apply additional coats. To check that the resin has reached the B-stage using a gloved finger press on the resin surface and it should feel tacky but no residue should stick to the glove.

  • Repeat the coating process as necessary and then leave it to fully cure.

Step 8: Flatting and Polishing

Once the resin has fully cured on the final coat it is time to flat and polish the surface up to the desired finish.

Flatting

The coating resin will be glossy but on closer inspection it will appear slightly uneven and could in places have high spots, runs or drips - these will all need to be flatted and finally polished using the following process:

  • Using a DA Sander starting with a 120 grit abrasive disc working evenly over the whole surface
  • check regularly to see if certain areas need more work
  • It is likely that in some places you may break through the resin into the carbon fibre, if this happens it will be necessary to apply another thin coat of resin to the part and allow it to fully cure before carrying on with this step
  • Now work through the grits from 400 grit and 800 grit
  • Then use finer grits, you may need a foam backing for the disc to increase contact and also spray with a water mist on the finer grits of 1000 and 2000
  • Regularly clean the pads to make sure there is no clogging
  • Clean the surface thoroughly before moving on to the polishing stage


Polishing

  • Polish the part, we used a coarse, diminishing compound which we spread evenly and sparingly over the surface of the part
  • Polish using a polishing machine with a soft pad.
  • Work the compound over the surface, keeping the pad moving to avoid excessive heating of the surface
  • Check that the surface doesn't get hot and if it does allow it to cool before continuing
  • You may find that you are happy with the surface result after polishing, or you may want to use a high-gloss finishing compound to bring it up to the finish we achieved
  • Apply this product and work it in the same way as the coarse compound


For reference: this size project took around 4 hours to flat and polish (with power sander and polisher)

Step 9: Trimming the Part, Removing the Foam and Adding the Final Touches

To complete the project we trimmed the wheel wells, cut out the hatch and removed the foam.

A cut line for the hatch is marked out and then the hatch is carefully cut using a Permagrit 19mm tungsten carbide cutting disc. The Wheel wells are trimmed using a flap wheel in a grinder to sand down the bottoms and expose the foam. The hatch is then removed exposing the foam.

Removing the foam is best done with a chisel and ripping it out by hand. Dig out all the foam and remove it from the finished part. The release film and peel ply is then easy to rip from the surface of the part. The finish left behind by the peel ply is ideal for any further bonding or laminating depending on the application of the finished part.


Finally to create the rebate for the hatch, we attached a strip of 3/4mm thick carbon fibre sheet with MMA adhesive (methyl methacrylate) and added our branding vinyl wraps to complete the look.

Step 10: The Finished Mouldless Carbon Fibre Construction

That's how you can produce a carbon fibre part without a mould, saving you lots of money and

We hope you have found this Instructable fun and educational and would love to hear any comments you may have or answer any questions in relation to the processes in the project.

This really is a great way to access working with carbon fibre and composite material without the need for expensive equipment or experience, we'll share more projects with you soon!