Hi, I wonder if you can give me some advice on fixings for carbon fibre strips.

I'm woking on a project at the moment which requires me to provide a hole in one end of a cbrbon fibre strip to act as a 'fixed' fixing point for a screw to go through and a slot at the other end to allow for movement in the finished article as it needs to retain a degree of flexibility in use. I'm undecided about width and thickness of the strip I will need but would appreciate some advice if there is a minimum you would not recommend going below to avoid the risk of cracking or splitting whilst drilling the hole.

For the slotted end would a router be suitable for cutting the slot out of the material? Also, I am new to using carbon fibre and wondder if there are any perticular health and safety issues in cutting the material - i would be using a mask and protective glasses as a matter of course, but would I need to consider anything other than that?

As an alternative, I am also thinking about possibly using a solid rod of small diameter as this would make some other design issues easier to deal with, but I am a bit stuck when it comes to figuring out how this might be fixed - is there any sort of end connector (see attached rough sketch) available which could be fixed to the end of a rod to allow it to be screw-fixed in place?

I'd be grateful for any guidance you might be able to give

Hi David,

Thanks for the post. When machining composite materials, particularly pultrusions (because they are made from entirely unidirectional carbon fibres running lengthways) you need to be particularly carefull to avoid compromising the strength of the rod/strip/tube etc. As soon as you drill or slot through the section, you break the continuity of the fibres and really leave yourself with something that is far weaker than it would have been before the machining operation. For this reason, the very best thing you can do it what you've already suggested in your diagram which is to bond some fixings (eyelets, rod ends etc.) onto the end of the rod/tube/strip so that you can keep the carbon fibre intact and then make your fixings to the metal, which is far better suited to this type of work.

I'm afraid that we don't have any such fittings ready to go but I really do think it's a good idea and so would always suggest that people either hunt-out or even fabricate something like this and then bond the carbon fibre into the fixing using epoxy adhesive like our ET500 Rigid 5 Minute Epoxy Adhesive.

Also, I am new to using carbon fibre and wondder if there are any perticular health and safety issues in cutting the material - i would be using a mask and protective glasses as a matter of course, but would I need to consider anything other than that?

When cutting and finishing carbon fibre a good dust mask, adequate ventilation and safety goggles are the essential ingredients. Nothing else is required. Localised extraction (like a vacuum cleaner hose held in place) can make the trimming operation cleaner and safer still.

I hope this helps.

All the best, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

many thanks for your advice - very helpful