General News
Carbon Fibre - A Mountain Bike Perspective - Tech Talk Series
Share on Facebook Share on TwitterPublished: 13th March, 2012
By cfrbikes.com
Those of you who have been around the sport for a few years will no doubt have moments when you think back to the 90s, a time of steel prestige, Tioga disks, and the unhealthy obsession with purple anodized bits.
You may even have an old relic hidden away somewhere, which despite your best efforts demonstrates that you too were part of this world!
If you were biking in the 90s this was what it was all about, a chain set with ratios to make a Tour de France rider cry, toe-clips, and lashings and lashing of purple (with maybe a dash of fading to orange for good measure)!
How things have changed!
One of most notable changes I am always stuck by is the incredible weight difference between yesteryears wonder race bike and today's. I mean is it that our old friends have been tucking into a few pies since been retired? From fully rigid race bikes weighing around 25Lbs, we are now seeing full sus steeds tipping the scales at a tasty 23Lbs, how? They still have two wheels, a seat, and a set of bars!
Part of this is thanks to the ever growing use of the wonder material carbon fibre, but what actually is it? Where does it come from? And how can something so light be so strong?
Over the next few weeks, CFR bikes, specialists in carbon frame repair, will be teaming up with XCracer.com to bring you a series of technical articles on carbon fibre from a mountain bike perspective. The articles will help to give an insight into this remarkable material, and hopefully remove some of the mystery surrounding it.
PART 1: Where does carbon fibre come from, and what is it?
When you look at a carbon fibre component you will more often than not see a black woven pattern which gives the appearance of a coarsely woven fabric coated in a hard translucent resin.
This is in actual fact exactly what it is, and is what is known as a composite, a material that combines the properties of two or more materials, to give a resulting material with improved properties.
The fabric is made up of weaving bundles of carbon filaments together in a variety of ways to optimise the properties of the composite in which the fabric will be used. (More on carbon fabrics in following articles).
The resin is fundamentally a very hi performance glue, and is commonly made from Epoxy, a two part adhesive which will only go hard when both parts (the adhesive and hardener) are mixed together in the exact proportions. (More on resins in following articles).
When layers of the carbon cloth are applied with resin and pressed together in a mould the carbon component is created. (we will come back to carbon lay up in a future article).
The basis of carbon fibre is continuous carbon filaments which are about 0.005-0.01mm in diameter.
A carbon filament running over a human hair.
These are produced using a chemical called polyacrylonitrile, an organic polymer. Through a complicated chemical process, a continuous filament is created which is then stabalised to alter the atomic bonding pattern by means of heating to around 300°c. The filament is then carbonised which consists of heating the filament up to between 1000°c-3000°c in an atmosphere devoid of any oxygen. This causes any non carbon atoms to be released, leaving a chain of carbon crystals made up of tightly bonded carbon atoms resulting in a carbon filament.
These filaments are then twisted into a yarn, which can then be woven into a fabric and used. It is when talking about fibres that the term modulus is often used. This refers to the tensile modulus or Young's modulus of the fibre. This is fundamentally a measure of the performance of the fibre, and is calculated by dividing Stress by stain. (Stress being defined as maximum load/ cross sectional area) and strain (being defined as change in length of the fibre divided by the original length).
The result is a value in pounds per square inch (PSI) or Pascals. As an indication a low modulus fibre has a tensile modulus of 34.8 million psi (240 million kPa), where as a high modulus carbon fibre has a tensile modulus of 72.5-145.0 million psi (500 million-1.0 billion kPa). As a comparison steel has a tensile modulus of 29 million psi (200 million kPa). Thus, the strongest carbon fibre is about five times stronger than steel! Combined with this, carbon has a density of 1740kg/m³ compared with steel which has a density of 7480kg/m³. So in conclusion, a carbon filament is about 5 times stronger than steel and 4 times lighter, making it a truly amazing material!
Next time on Carbon Tec talk:
How can things made from carbon fibre be so strong, yet so light?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
About the author:
CFR bikes was set up in response to growing need to offer a means by which damaged carbon fibre bicycle frames could be repaired.
Be it a mountain bike frame or a road frame, CFR bikes are here to get you back riding as soon as possible, and without the costly option of having to replace the carbon frame.
So whether your frame is cracked, holed, has a loose bottom bracket insert or broken cable stop, we are here to help.
Broken frames simply need to be sent to CFR bikes upon which they will be repaired, and returned.
Simply go to www.cfrbikes.com for details.
The people behind the operation.
CFR bikes was founded by Peter Hawkins a mechanical design engineer and long time mountain bike racer. During a work experience placement in 1995, at the carbon bicycle manufacturer Hotta, based in Totnes, Peter became interested in composites, and went on to study mechanical design and manufacture at the University of Plymouth. Upon graduating, he went on to work as a chassis design engineer at Jaguar Cars Ltd in Coventry.
During 2002, Peter and his brother James, also a mechanical engineer and bike nut, began making bikes, beginning with a homemade tandem that made it round the Newnham 90 enduro event! The following years saw ever more complicated and better bicycles being made, first from steel, then Aluminium, and finally carbon fibre. These bikes ranged from full suspension tandems to commuter specific bikes, peaking in 2008, when Peter Hawkins rode an aluminium and carbon composite full suspension bike to victory, in the X-terra off road triathlon world championships in Maui USA.
Peter Hawkins on his way to qualifying for the World Terra championships in Sardinia in 2008 on the home built "Preston" carbon and aluminium full sus, before going on to win his category at Maui on the same bike.
Combining his skills as a mechanical engineer, together with the first hand experience of actually working with, and making components from carbon fibre composites, Peter has developed a range of techniques which he has used over the years to repair numerous carbon frame issues ranging from chain damaged chain stays, to lose bottom brackets, to broken or loose cable stops on brands ranging from Cervélo to Scott, to Giant TCRs.
This road frame suffered from a broken seat stay, but thanks to CFR it was repaired and is now back on the road!
If you have a carbon frame which needs a bit of TLC get in touch with CFR bikes at www.cfrbikes.com for more information.
Related Articles
Carbon Fibre a mountain bike perspective resin
CARBON FIBRE - A MOUNTAIN BIKE PERSPECTIVE - so strong yet so light
Contact Us | Advertise | Use Our Online Entry System
All content © XC Racer.com | Website Designed and Developed by DesignUNLTD