About Carbon Fibre

WHAT IS CARBON?

When people talk about carbon they usually mean carbon fibre composites. These carbon fibres are embedded in a matrix of plastic. Carbon fibres are industrially produced fibres made from raw materials containing carbon, which, by means of thermal processes, are set into a graphite-like order. Carbon fibres are extremely light and of enormous tensile strength. To technically use the only 5-8 µm thin filaments either as rovings (skein) or as unidirectional fabrics they are included in a plastic matrix.
The first parts made of carbon fibre reinforced plastics (crp) appeared around the end of the 80s, back then they were made of “dry” carbon fibre fabrics, which were then soaked with liquid resin.
Some time later so called “Prepregs” became popular, “Prepreg” being short for “preimpregnated”. These Prepregs came immersed in a still wet plastic matrix, which makes for a better quality of the laminate with a more even distribution of the resin.
Schmolke Carbon was there right from the start. We learned our first lessons with „dry” carbon fibre fabrics already. Our understanding of quality made us moved on to Prepregs at an early stage already, even though back then Prepregs were still so rare (read: expensive) that they were only ever used in aerospace applications. Over the years the quality of the raw materials, the fibres in particular, improved, as did the quality of the Schmolke products. The evolution of the fibres since 2000, for example, equals an increase in ultimate tensile strength by the factor two. At Schmolke it has always been our policy to use the best materials money can buy, hence our head start has grown into a constantly growing lead in technology.

WHAT MAKES CARBON FIBRES SO SPECIAL?

Carbon fibres and the products made of them are characterised by outstanding strength and stiffness while being extremely lightweight at the same time. Carbon fibres are also remarkable for their „anisotropy”. So what does that mean? Metals for example withstand loads regardless of their direction. This property qualifies them for „isotropy”. In contrast to that plastics reinforced with carbon fibres survive loads in the direction of the fibres much better than loads perpendicular to the strands’ direction. They excel when it comes to tensile loads, for pressure loads they are not that good. This variation of characteristics is called „anisotropy”.

The material’s anisotropic nature can be used to advantage though. If one analyses the loads prevalent in a specific situation it is possible to lay the fibres only in the directions where they are actually required, thus saving both material and weight. This requires a thorough and deep understanding of loads and tensions a particular part has to withstand, and a fibre layout taking these factors into account. Years of experience with the construction and the manufacturing of carbon fibre parts are simply indispensable when it comes to making parts, which benchmark quality and performance in their field.

HOW TO FIT THE PARTS?

Tensile loads are carbon fibres forte. Bending loads always include tensile loads; hence they do not pose a real challenge for carbon either. Carbon fibres’ advantage is less evident with multi-axis-loads (that’s loads with different directions). These pressure situations are usually typical in places where the parts are compressed, as in clamping areas. We analyse the character of these stresses and reinforce our parts in the relevant places. Since we do not want to add excessive weight it is essential to define limits for these local loads. Please follow the recommended maximum torque settings and do not clamp the parts outside their marked reinforced area. However tough carbon fibre parts may be, clamping forces are their Achilles’ heel!

WHAT MAKES SCHMOLKE PRODUCTS DIFFERENT?

As usual quality comes at a price. Schmolke Carbon has defined the goal to be a lightweight and intelligent construction at the same time. This means, we design our products according to your demands and usage. The rider’s weight and style of riding is as important as the mileage. Custom-made parts are not only defined by their sizes and diameters, first and foremost it is the layering of the fibres, which makes each part unique. Each and every handlebar and seatpost are made to purpose, by hand, meticulously following a specific layout. This fibre layout shaves the grams off the parts – while leaving enough of a safety margin to survive even out of the ordinary situations.
In order to guarantee the highest possible quality we develop and manufacture all our parts in Germany.
Another factor which sets us apart from other, and possibly cheaper, producers is that we use only the best quality of fibres Toray, leader of market and technology from Japan can supply.
As illustrated by the diagram below the T1000 fibres we use in our TLO range have a tensile strength some 30% higher than the tensile strength of the T700 fibres more commonly used in the bicycle industry. The T1000 fibres cost twice as much.

Not the least contribution to Schmolke’s proven quality is our attention to detail. We use numerous thin plies because this is necessary to precisely model relevant loads. As a side effect multilayer constructions also improve fatigue strength, that’s the life span of the part. On top of that more layers make for a less sudden and unpredictable failure if the parts should break. Unlike simple designs with only few plies of many thin layers do not make the part “brittle” with a tendency for sudden failure; they are more reliable and safer.

THE K-FACTOR – WHAT IS 1K, 3K AND 12K?

Over the last couple of years marketing people have used terms such as 1K or 3K when writing about carbon. This specifies the number of miniscule fibres (filaments) used in one roving. 1K stands for 1000 filaments, 3K for 3000 and so on.
These rovings are then biaxially interwoven to make a carbon fabric. The differences between the fabrics are mainly in the looks.

UD – WHAT’S THE STORY?

UD is short for unidirectional. This means, that all the filaments lay parallel in one direction, no cross fibres or weaving. Things such as 1K, 3K or 12K are therefore of no importance at all. The only thing of relevance is the total number of fibres used, that’s the weight of the plies relative to the area. This is something marketing writers usually do not mention though.
UD is different to fabric not only because of its look, its mechanical properties are also different: In a fabric the fibres are slightly bent because of the weaving. This leads to a slightly reduced tensile strength; the fibres are not as straight as would be ideal. Fabrics with their mesh of filaments stop cracks better in the case of failure though.
UD fibres may therefore be not a bad idea for frames, where more than one tub supports the weight of the rider. The failure of one tube does not necessarily lead to a crash. For our parts we are not happy with the UD trend. If so desired we will make handlebars and seatposts with a UD surface layer, we will always use fabric underneath for safety reasons, it helps to prevent “brittle” breaks and a rapid expansion of cracks 

OVERSIZE VS. 26/25,4 MM DIAMETER

The trend to go oversize, that’s handlebars with 31.8 mm diameter, needs to be evaluated from different points of view. In general, it is true, that larger diameters with reduced wall thickness make for an over proportionally stiffer part with the weight remaining the same. With this in mind it would surely be a good idea to blow up the diameter and reduce wall thickness accordingly.
There is a limit to that though. The thinner the wall, the more fragile against pressure they become and – enter the well-known Coke-Can effect – they tend to dent easily. Since carbon fibre is much better at withstanding tensile loads than it is at withstanding pressure, it does not lend itself to the oversizing trend. With the pressure forces typical for the clamping of the bars by the stem this area needs to be reinforced.
Our oversized roadbar, the lightest in the world, weighs 5 g more than it’s standard-sized counterpart with 26 mm diameter. Still it features an ergonomic rest for the hands and it is stiffer, because the larger diameter is kept throughout the whole midsection of the bars.

DOES SCHMOLKE CARBON OFFER A WARRANTY FOR ITS PRODUCTS?

The relevant legal warranty period is 24 months. We go one better and cover all products with a three-year warranty. Outside of our standard warranty we also offer lifetime crash replacements. Crash replacements are determined case by case depending on product age. If you need a crash replacement, please send a copy of the invoice and a short description of the damage and photos to info@schmolke-carbon.de and we will get back to you within 48 hours.

WHAT DOES „SL” STAND FOR?

“SL” stands for “super light”. For our seatposts and handlebars we use T800 quality fibres for this line of products, whereas other manufacturer’s carbon fibre parts usually make do with anything from T300 to T700. In addition to that we know how to build carbon fibre parts, these two factors combined lead to the combination of low weights and reliability we stand for.

WHAT DOES “TLO” STAND FOR?

“TLO” –” the lightest one”. For this line of seatposts and handlebars we simply use the best money can buy, that’s T1000 fibres. Their tensile strength is yet another 16% higher than that of the T800. In addition to that our TLO laminates use yet a more difficult layer structure. The combination results in numerous world record weights; lighter still than the SL without compromising either reliability or stiffness.

HOW SAFE ARE SCHMOLKE CARBON PRODUCTS?

Prior to the start of production, we test our parts on a test bench specifically by us to do that job. Our test procedures comply with the standards defined by the new DIN EN 14781 and 14766 norms. Once we’re through with that we go one better and start our own, much harder test sequences. Under up to 150 kg of load the bars flex up to 30 mm!
Once production has started we continuously test samples to improve our seatposts and handlebars.
We are still not satisfied though. A testbench is only a testbench, so we take our stuff out to the roads and trails every day. There are two MTB Pro teams who ride and race our TLO parts.

 

WHY DON’T YOU PAINT YOUR PARTS’ SURFACES?

Our parts’ surfaces are not as shiny and polished as the surfaces of parts made in China. There is a reason for that: we do not paint our parts.
Paint doesn’t make the parts any stronger, it makes them heavier though. Most of the time the gloss doesn’t last that long anyway, paint often is quite sensitive when it comes to scratches and to exposure with chemicals. Our epoxy resin surface usually is much sturdier.
Still we like our parts to look as nice as painted, because of our extremely long experience and our optimized manufacturing processes with mirror like polished moulds.

 

CAN YOU REPAIR CARBON FIBRE PARTS?

As with most other high-end parts made from aluminium or titanium repairs are usually not economic. We would have to x-ray the part and check it with ultrasonic, both of which is very expensive and still does not give a fully reliable result.

DO CARBON FIBRE PARTS HAVE TO BE REPLACED AFTER EVERY CRASH?

In general any crash is a major incident for your handlebar. It may damage its internal structure terminally. In this respect carbon fibres are no different to other lightweight materials such as aluminium alloys.
For your own safety you should thoroughly check all components after a crash. If in doubt do not continue to use them but replace them or check with the manufacturer.

If your handlebar shows one or more of the following it is certainly damaged:

• Thorough visual inspection: visible cracks in the handlebar.
• Application of load: Pull, push and turn into different directions with the handlebar secured in the stem. If one side is noticeably weaker than the other it is damaged.
• Application of stress: Handlebar makes strange sound under loads while being secured in the stem.

If your seatpost does one or more of the following it is certainly damaged:

• Thorough visual inspection: Visible cracks in the seatpost.
• Application of load: Seatpost can be bent into one direction more than into another.
• Application of load: The seatpost makes strange sounds.

Please keep in mind, that the above is a guideline based on years of experience. Still we cannot possible guarantee a part after a crash even if none of the above is evident. If in doubt replace the part. Your safety should have highest priority!

Be careful with second hand carbon fibre parts! There isn’t a chance really to check what happened in its life before you bought it. At the end of the day what appeared to be a bargain may pose a considerable danger to your health.