Yesterday, we got a very nice and awaited for package from R&G GmbH:
Most probably you are wondering what these strange black rings are. Well, these are pultruded carbon profiles. To be precise twelve rolls à 50 metres with a cross section of 20 × 0,5 mm and a fibre volume ratio of over 60%. Half for me and half for a friend. Ok, but what are the profiles for? It’s for the spar caps. So, we got a delivery for one of the most important pieces of the wing—and thus the airplane. A good reason to feel like having Christmas!
Depending on the mechanical stress, several layers of profiles will make the spar caps up. The profiles have perfectly oriented carbon fibers and a very high fibre volume ratio. Much higher and more reliable than a self made roving spar cap. Unidirectional pultruded profiles are predestined for caps, which are mostly subjected to axial stress.
The last two months we made some intensive investigations on the properties of the profiles:
Flexural testing of carbon reinforced beams can be quite intimidating:
To be honest, I had not the courage to break the beam shown in the last photo. It provided some very good data, though:
Having the data, I calculated the amount needed for the wing and we could place our order at R&G.