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It has been suggested by some people that Ultrasound scans aren't useful because they don't find cracks and cannot differentiate between fillers used during manufacture and real defects.

It has even been suggested that because bikes are not aircraft, you don't need the same level of quality or care!

 

As a person with over 25 years Non DEstructive Inspection experience that has held CASA (Civil Aviation Safety Authority), certification as well as the equivalent FAA and a range of military approvals, I can answer these questions accurately.

 

Cracks that are perpendicular to the laminate plane are dificult to find with Ultrasound, however in carbon composite there is usually delamination associated with a crack. Delamination is easily found as it is a planar defect which Ultrasound is the proven method for detection. Cracks on the surface are also visible, therefore can easily be found by visual inspection, unlike internal delamination which cannot be found visually..

Using a combination of methods instead of being limited to only one method is the best approach for detecting, identifying and sizing damage and defects.

 

Fillers are sometimes used, it was common to find fillers on many older frames however the latest frames tend to use very little as the moulding methods have improved. Fillers also add weight to the bike which is undesirable so they avoid it's use where possible.

We know this because we section cut frames to see how they are built and use these as Ultrasound reference standards.

Ultrasonically, the velocity of sound of the fillers used is a little different to resin and carbon, which also varies due to fibre volume, type and resin content. The key ingredient using Ultrasound is experience and the difference is quite obvious between fillers and rejectable indications. The Ultrasound display may show a small interface which the inexperienced may see as a defect, however a back wall signal (the internal face of the part) will still exist. With a delamination the back wall signal will be scattered or may even disappear, so the experienced technician can tell the difference between fillers, voids, porosity, foreign object and delamination. To pass the CASA level exams you have to be able to do this.

Of course another big advantage of having Ultrasound scan capability is that we can ensure that our repairs (or other peoples repairs) do not have porosity or voids and are laminated correctly. So apart from finding all the damage, we can also provide the same level of confidence that the repair is sound as well. Without the scan you just don't know how good the repair is internally.

The level of care in aerospace has always been at a higher level than other fields such as automotive, boating etc. Be thankful that when you step on board an aircraft, they use Ultrasound scans to avoid catastrophic failure, not only on carbon parts but metal parts as well.

 

I don't know about you, but when I am flying (pun intended) down a big hill on my bike, I like to know that the highest level of care has been applied to avoid a component failure causing a crash with potential serious consequences.

 

I apply the same standards to your bike and that is why we are the "Gold Standard" in carbon bike assessment and repair.