The assessment of frames and components made of carbon is particularly critical, because overloads affecting this highly sophisticated composite material made of carbon fibres and resin are not necessarily visible in form of external damage as known from metallic components made of aluminium or steel.
To a cyclist the question therefore arises whether his/her bicycle with carbon frame and carbon components has suffered damage after an accident, fall or mere toppling over or whether he/she can continue riding on it. Retailers and manufacturers typically recommend a replacement due to a lack of reliable testing, even though this would not be necessary in many cases.
More than 25 years of experience with materials
This is an issue the team around graduate engineer Dirk Zedler has been dealing with for nearly 25 years. As a solution we have developed test procedures and test routines ensuring reliable testing of carbon frames involved in accidents. Simple x-raying procedures as well as the often cited random impulse thermography do not deliver reliable results, according to our experience. As these methods usually allow the assessment of a component’s condition only, if respective photos of the condition as new or precise construction details are available for comparison at the same time.
Stiffness tests are part of our testing routine. They produce values referring to the physical characteristics actually existent. These values are then compared to the values of components in the condition as new. One side effect of these stiffness tests is that possible cracks become visible under load and damage to the material audible by the typical noises caused by alternating loading and unloading. Furthermore, we are able to detect possible local damage by means of additional examinations. These procedures have been continuously refined and meanwhile applied by a few manufacturers, as well.
Moreover, we have access to high-definition computer tomography. This high-tech procedure can be employed for further analysis, e.g. to analyse the reasons of fracture.
Understanding of specific characteristics
Our power of judgement in this respect is based on the practical experience of our team members. They commute daily by bike or e-bike and in their spare time they also use their bicycles for cycle trips and other activities, such as training or competitions in different disciplines. On the other hand we are able to draw on 20 years of experience as technical bicycle experts and numerous concluded expert's reports as well as documented loss incidents. In addition, we are able to reliably assess durability and typical bicycle and pedelec component damage on the basis of thousands of fracture patterns. The latter were created during tests (until failure) in our in-house laboratory and are recorded in our company archives where they are accessible at any time. Our wealth of experience is particularly large in the case of bicycle components made of carbon; in case of damage their overload behaviour is fundamentally different from that of components made of metallic materials. The basis for that was laid by company founder Dirk Zedler in 1986 with his first practical and scientific works and ever since the expert knowledge on fibre-reinforced composites has increased continuously.
Focus on severe claims
The experts of GDFS draw up expert’s reports on bicycles, pedelecs and individual components made of carbon at a value as new of more than 2000 Euro. Expert’s reports for less expensive products are drawn up, in case of an insufficient plausibility of the incident of loss or if there are insufficient grounds for the claim for damages.
Reliable carbon tests are only profitable in the case of carbon frames and wheels. For all other components, such as handlebars, saddles, forks etc. replacing the component is the better choice.
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