Around four years ago, Professor Phillip L. Manning of The University of Manchester’s Department of Earth and Environmental Sciences and Kevin Pickup, lead technologist – product verification at BAE Systems, met at an X-ray conference.
They chatted about parrots and sixth-generation fighter aircraft and, as a result of that fateful day, four years later Nature published a paper called ‘Harnessing 3D microarchitecture of pterosaur bone using multi-scale X-ray CT for aerospace material design.’
The lead author of the paper, Nathan Pili, a PhD student at The University of Manchester, explains to Runway Girl Network: “Phil and Kevin got chatting” at the X-ray conference, “Phil about dinosaurs, pterosaurs and fossils, the cool stuff that gets everyone’s attention, and Kevin about fighters.
“Kevin has a pet parrot, and the conversation turned to the adaptations parrots have for flying, sparking the collaboration that led to the research. They brought it to me to bring the information together in a PhD project as a pilot for this new ‘paleo-aircraft’ field; for my Masters, I had CT imaged titanium powders for additive manufacturing.”
Pili’s subsequent study applied advanced techniques in X-ray computed tomography (CT), pushing it to its limits and producing detailed images of ‘slices’ or ‘sections’ through a sample.
The University of Manchester notes that fossil bones were scanned at near sub-micrometre resolution, resolving complex structures approximately 20 times smaller than the width of a human hair. “3D mapping of internal structures permeating the wing bones of pterosaurs has never been achieved at these resolutions (~0.002 mm),” it states.
3D renderings from Pili’s CT X-ray work. Image (a) has the upper half of the bone rendered transparent to show the network of spaces, or canals. In (b) the canal volume is rendered semi-transparent to better show the canal positioning. Image c) shows the canal network parallel to the bone’s longitudinal axis and (d) the reduced concentration close to the bone’s edge. Much larger canals, 20μm (micron) or more in width, are highlighted in red in (d) and enlargement (e). (via Nathan Pili)
Pili discovered networks of minute weight-saving spaces or canals throughout the bones. These might also have carried nerves or other biological structures, and Pili realized that in aerospace materials manufactured to mimic pterosaur bones such spaces could accommodate sensors; they might be engineered with self-healing materials or, in future, perhaps with control or power architectures.
“For centuries, engineers have looked to nature for inspiration — like how the burrs from plants led to the invention of Velcro. But we rarely look back to extinct species when seeking inspiration for new engineering developments — but we should,” he says.
“We are so excited to find and map these microscopic interlocking structures in pterosaur bones, we hope one day we can use them to reduce the weight of aircraft materials, thereby reducing fuel consumption and potentially making planes safer.”
Previously unpublished images provided and described by Nathan Pili: 1) shows a normal photograph of the bone, and 2) is a macro CT scan of the whole bone, whilst 3) is the orange square in 2) when we micro CT scanned it. The resolution on 2) is 50 micron pixel size, and 3) is a 2 micron pixel size, showing around 25 times more detail! (via Nathan Pili)
Runway Girl Network directed Luca Wedge-Clarke, a design engineer at general aviation composite manufacturing specialist Swift Technology Group to Pili’s paper. Wedge-Clarke believes that a material manufactured with spaces in the region of 10-100μm across would provide an opportunity to incorporate the kinds of technologies Pili envisages.
Wedge-Clarke was more excited about the nearer-term possibilities for lightweight materials. “The core thesis of Nathan’s thoroughly researched paper appears very promising. If, as he suggests, a 16% density saving can produce a degradation in mechanical properties of only 3-4%, then an aerospace material produced on that basis would be incredibly useful.
“Where contemporary composites mostly use fiber reinforcements aligned to the load directions, it appears that pterosaur bones contained voids at a comparable scale, aligned the same way. The effects are different: where fiber reinforcements increase weight slightly for an outsized increase in mechanical properties, it appears voids decrease weight for a marginal cost in properties.”
Wedge-Clarke continued: “Porosity of the kind Pili describes is undesirable in traditional materials owing to its weakening effect and propensity to propagate cracks, but he describes the opposite effect. It would be very interesting to explore this element further.”
Nathan Pili is not the first to see aerospace potential in pterosaurs. During the mid-1920s the UK’s Westland, now part of Leonardo, began trials with a series of tailless aircraft under the generic name Pterodactyl, after the prehistoric creature whose Greek moniker means ‘winged-finger’.
Pili acknowledges the role he now has in helping industry understand and potentially manufacture materials based on his research. “The pterosaur wing should not have worked. With the CT project I think we’ve begun to understand how it did, and now we need an even deeper understanding to help apply what we’ve learned to aerospace.”
Nathan Pili, PhD student, Department of Earth and Environmental Sciences, The University of Manchester. (via Nathan Pili)
Related Articles:
Featured image credited to Nathan Pili, The University of Manchester
