Hello,

I'm looking to run a finite element analysis to determine which of your standard tubes would be most suitable for use as wishbones. Would it be possible to get information on the lay-up of your standard tubes? Particularly the 14mm ID and 18mm ID tubes.

Also I'm a bit unfamiliar with the roll wrapping process and was wondering if the process electrically insulates the tube on the inside in any way so as to avoid corrosion as it shall be in contact with aluminium.

Lastly I was hoping to find out if you offer a tube cutting service before sending the tubes out for delivery as I would not be confident in our ability to cut the tubes in our workshop here.

Thanks,

Stuart

Hi Stuart,

Sure here's the layup schedule for those tubes:

[0, 90, 0, 90, 0]

0 deg layers are 300gsm Toray T700
90 deg layers are 300gsm E-Glass ~UD (80/20)

With Regard to electrical insulation, the simple answer is no the inner ply is carbon so in will conduct, although in practice you will not see any deterioration to the interface within the typical lifespan of a component; light aircraft are only now seeing any form of galvanic corrosion between aluminium and carbon after 20 years of use, and even in these cases I don't know of any component failures, The problem will require an electrolyte such as salt water, the problem may well occur more rapidly in a harsh environment such as marine componentry.  I can understand your concern, if you wished to insulate between the insert and the tube you could use a method commonly found in the aerospace industry which is to wrap the insert with a single ply of 25gsm glass cloth and epoxy resin allow this to cure with a peel-ply and then remove the peel-ply and bond the insert into the tube. however in theory if used with the correct gapping, adhesive should separate the components sufficiently.

I am aware of many Formula student teams (which I'm guessing that this is) successfully use the 14mm and 18mm tubing as wishbones with aluminium inserts bonded in directly.

I would suggest this epoxy adhesive it is used extensively in critical motorsport and aerospace applications and has excellent performance under high frequencies, the inserts and tube will need to be prepared properly; the insert should run approximately 1.5 times the tube diameter into the tube, in your case with a 14mm I.D. that would be 24mm, the end of the insert should feature a shallow bevel to reduce point loading, knurling of some description on the body would also be desirable as the adhesive will then achieve a mechanical lock. The inside of the tube should be prepared with a good abrasion with 120grit abrasive. To assist the load transfer a lip stop on the insert will help to ensure an even loading into the tube under compression.

With regard to tube cutting, unfortunately we cannot offer this as a standard service for various reasons, however the tube is very easy to work with, even careful cutting with a hacksaw will give good results, I would always advise cutting slightly oversize and sanding back to your final length, this will leave a really clean edge.

Paul Statham
Easy Composites / Carbon Mods - Technical

Fantastic advice, thanks very much. And yes, this is for a formula student car!

Hi Paul,

Alike Stuart, I too, am on the process of selecting our wishbones and modelling them through FEA.
The information you gave is indeed very useful, although it is unclear to me the layers of 300gsm E-Glass... what is E-glass??? Is it an epoxy of some sort? I thought the rods would have been mostly in carbon fibre...
What kind of Modulus would the E-glass layers have?

Cheers,
João

P.S.: it too is for a Formula student car

Hi João,

E-Glass is a type of glass reinforcement, it is pre-preg E-glass that is used along side the pre-preg carbon fibre. It represents only a 2/5 proportion of the reinforcement in our carbon fibre tubes and is used because it has properties which aid the manufacturing process whilst at the same time providing strength. Remember that the carbon used is high modulus T700 to more than compensate.


Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Hi 

Hi Roxane,

Answers to your questions as follows:

1. UD 80/20 means that the E-Glass is primary unidirectional with 80% of the fibres running down the warp direction but stitched together by 20% glass fibres in the weft direction.

2. There are five discreet layers of reinforcement in the tube, the first layer onto the mandrel is the T700 UD carbon, then there is a layer of the glass at 90' to provide hoot strength, then another layer of T700 going lengthways down the tube, one more layer of glass and then the final layer of T700 which is what you see on the outside.

3. Type 'Toray T700 tds' into google and the first thing that comes up is the Toray T700 Technical Datasheet. You'll find mechanical data for E-Glass fibres here on matbase. To find the thickness of each layer, take the wall thickness of the tube (listed on the product pages for each tube) and divide it by 5.

Best regards, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Thanks. Great explanations!

Hi Roxane,

I can't provide a datasheet for the pre-preg glass but I've provided the mechanical properties for the glass fibres and you know that they are 80% warp, 20% weft and you even know the thickness of the layer and the density of the glass fibres so you should be able to derive anything you need for your simulation from this.

Best regards, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Hi

I am going to use some of your carbon fibre tubes  (50 and 60mm diameter). Are they have the same mechanical properties as you mentioned in previous post?

I also need your advise on which adhesive is suitable for them. I need to bond these carbon fibre tubes with aluminum ones in order to carry heavy weight (3000-4000 Kg). Any suggestion?




Thanks

Rahh