About carbon repair
The look & ride feel of your bike can be maintained without compromising safety. We use pre-preg Carbon Fibre & quality equipment and processes to deliver Australia’s best Carbon Repair. We fix Carbon Fibre breaks, cracks or gouges in frames, stays, top/down tubes, wheels & other carbon fibre parts.
Carbon fibre repair techniques
STEP 1 - DAMAGE ASSESSMENT & REPAIR STRATEGY
Most of the damage sustained by carbon fibre bikes are cracks / fractures of one of the carbon fibre tubes. These cracks / fractures may be either be transverse or longitudinal cracks.
Ultrasound is used to determine the extent of damage, including the thickness of the part of the bike and map out the damaged section. We then develop a tailored repair strategy for each repair. We never cut out sections of tubes to “repair” them (unlike some competitors) as this is structurally unsound and does not meet the criteria for safe repair recognised by the aerospace industry.
STEP 2 - REMOVE DAMAGE & PREPARATION BY TAPER SANDING
To prepare the site, the damaged carbon fibre is removed by abrasion & sanding to form a crater until the crack or damage has been ‘chased out’, i.e. no further damage can be seen. The sides of the crater are sloped (very shallow) so that each to the layers become visible in concentric like circles or ellipses. We look to achieve a minimum of 30:1 overlap of each of the carbon fibre layers. This will re-establish the original strength when replaced by carbon fibre plies. This method is called a ‘scarf’ repair.
STEP 3 - CUT OUT REPAIR PLIES FROM PRE-PREG CARBON FIBRE SHEET
A number of repair plies (i.e. carbon fibre layers to be used in the repair) are cut from a sheet of pre-preg unidirectional carbon fibre to the shape of the ellipse in increasing sizes with the correct orientation of the carbon fibre.
STEP 4 - SET REPAIR PLIES IN PLACE
The ply location template is used to trace the shapes of each ply onto the pre-preg carbon fibre ensuring the correct angle of orientation. The plies are then arranged in order and pressed into the scarf site and ‘de-baulked’ – i.e. air removed – and ready for curing.
STEP 5 - HEAT BONDING
A localised heat (hot-bonding) process is used to create a strong thermoset bond and cure the repair under pressure, resulting in a uniform & level repair with only the minimum of finishing required. The repair becomes fully integrated with the original structure.
We use proprietary localised hot bonding equipment and techniques rather than using an oven for your complete frame. Total immersion of bike frame in a commercial oven for curing the carbon fibre repair risks further damage due to different thermal expansion rates of metal and carbon fibre and potential paint discolouration and damage to thermal graphic transfers.
Tech talk: Carbon Fibre Bike Construction
HOW IS MY CARBON FIBRE BIKE MADE?
Your Carbon Fibre bike frame, tube or part is made up of many different layers of carbon fibre and epoxy resin. The direction & orientation of each layer decides the structural properties of the product. Having many different layers helps take loads coming from different directions, so you can design the material to be strong in the direction that the product needs to be while being as light as possible.
When we repair your bike matching the existing layup of the repair area is therefore important to retain the designed characteristics of the bike, i.e. seat stay may be designed to flex or the top tube needs to have torsional stiffness.
PRE-PREG CARBON FIBRE VS WET LAYUP
There are two main methods to produce the carbon fibre composite - use of pre-preg carbon fibre or wet layup of carbon fibre.
PRE-PREG (PRE-IMPREGNATED CARBON FIBRE)
The thermoset resin is impregnated into the carbon fibre by the manufacturer in a controlled environment. In this controlled environment, the resin has the viscosity of water, this ensures the fibres are “wet out” soaked in resin and not just coated.
The exact/ optimal fibre to resin ratio is achieved 33% resin to fibre (no excess resin required). Which gives the product the best strength to weight ratio. This is why bikes, formula one cars, planes and any other quality carbon fibre product is made using this material and method. It costs more but is roughly 70% lighter than wet carbon fibre of the same strength characteristics.
Thermoset resins in pre-preg re-soften (Glass Transition Temperature Tg) at a higher temperature – 120 Degrees Celsius.
WET LAYUP / TRADITIONAL HAND LAYUP
Traditional hand / wet layup is when a dry fibre/ fabric is used and is wet out with a two-part room temperature cured (chemical reaction) resin. The maximum strength properties of the composite material in wet/ hand layup cannot be reached due to 50% resin content being the best that can be achieved. This means that the finished composite weight is 50% fabric and 50% resin.
Typical hand laminates, even when vacuum bagged, end up with a significant amount of excess resin. Excess resin increases the brittleness and reduces overall properties. On the other hand, most pre-pregs contain around 33% resin. This is the ideal resin to fibre ratio for optimal strength/ stiffness/ lightweight properties and generally impossible to achieve in normal wet/ hand lamination.
Wet lay-up resins used in hand layup re-soften (Glass Transition Temperature Tg) at a lower temperature – 80 Degrees Celsius.
Searching for Carbon Fibre Repair on the internet often results in products advertised for DIY carbon fibre repair, which includes a little jar of resin. This is a wet layup technique and should not be attempted by the home user. There are lots of videos of people who have repaired their own bikes, but this is a recipe for disaster. We don't recommend you ever do this. Talk to us - we are experts in carbon fibre repair.
WHY SHOULD PRE-PREG ONLY BE USED?
- It is what the frame was originally made from.
- Superior mechanical properties – resin to fibre ratio.
- Will not re-soften in a hot car.
- Takes out the human factor of mixing resins and hand wet out/ excess resin.
- You can be much neater and more precise with pre-preg.
- Lighter and stronger as per original – resin to fibre ratio.
- No extra material needed so the shape of your frame can be retained. No bulge or over wrap.
- DIY kits using wet layup bought on the internet will not deliver a safe or reliable result.
Amazing workmanship, short turnaround, great value. Highly recommended.
Brett Hosking, Customer
All repaired within 3 days-great job thanks so much!