Modelling of a pterosaur wing
This section draws on mainly on chapter 6 and 7 of my thesis, which can be found on the PhD page.
Using the approach and calculations described in my PhD, I have been experimenting with making models of possible pterosaur like wing membrane material. The structure was most likely highly anisotropic since it appears to have comprised a skin like material (perhaps like bat wing?) reinforced with thin, unidirectional fibres called actinofibrils; most likely made from keratin, which has a much higher tensile stiffness than the surrounding material.
In nature the actinofibrils are very fine indeed and packed closely together (there are many good references on this, but Chris Bennett’s 2015 paper is arguably the most comprehensive (and can be found amongst my list of references.) It was impractical to model these structure one to one, so I experimented with a range of different combinations of thin threads and spacings to give material with the correct load extension properties. These experiments are described here.
The latest incarnation is a 1.5m long wing which is waiting for the wind to drop so I can test it. I have set up a long zip wire in the garden and “fly” the wings on that, recording speed with a GPS and taking video of the way the membrane behaves. This is what the latest model looks like in anterior view. Note that the humerus is raised relative to the horizontal, but still the wing tip is ventrally depressed. This degree of curvature was not in the unloaded wing spar – it was only gently curved ventrally to reflect the curvature seen in the few fully 3D preserved wings bones that are available.
What happened was that as the membrane was attached to the wing spar, it induced not only a-p but also d-v curvature – a result I think of the unbalanced structural sections of the distal wing bones, where the vertical stiffness is only around half that in the a-p plane.
The picture below shows the wing in dorsal view.
