Nav: Home

Researchers explain why feather shafts change shape when under stress

December 12, 2016

Researchers at the University of California San Diego for the first time have revealed why the shape of the feather shaft changes from round to square when it's put under stress in a paper published in recent issue of Advanced Science. Nature almost always favors roundness. Only under special circumstances does it opt for square shapes. Examples include the cells of plants -- which derive their name from the square cells of monks. At a larger, structural level, there are a few rare examples: the seahorse tail, a vine found in the Amazon that has a square cross section, and the feather rachis.

In their study, using fundamental mechanics equations and experiments in modeling materials, researchers show that the square shape provides greater rigidity and higher resistance to ovalization and buckling than a hollow round shape of the same weight. "The most amazing thing is that this reflects textbook mechanics," said Marc Meyers, the paper's senior author and a professor of mechanical and aerospace engineering at the Jacobs School of Engineering at UC San Diego. "And obviously, birds haven't studied that subject."

Ovalization can be observed by subjecting a drink straw to progressive bending: the section will gradually change from round to oval, and the stiffness is correspondingly decreased. But the feathers of flying birds, with a round-to-square sectional shape, retain their rigidity intact in spite of bending. By contrast, non-flight feathers, such as flightless ostrich wing feathers and peacock tail feathers, are not subjected to the same constraints and their shafts do not change from round to square. This is because a feather is a highly specialized appendage that enables birds to fly, generating thrust and lift. Its mechanical properties are optimized and weight minimized.

The feather-shaft cortex is a fibrous composite with varying fiber orientations along the length adjusting to local stress requirements: the increasing amount of axial fibers ensure sufficient flexural rigidity, while the crossed fibers provide reasonable flexibility and torsional rigidity.

The features revealed symbolize the unique adaptation of feathers for optimized stiffness and lightness, a natural structure inspiring for advanced engineering designs.

"Nature is indeed wondrous," said Bin Wang, the paper's lead author and a member of Meyers' research group. "And it is such a beauty to look at nature with human knowledge."

Wang and Meyers said that the findings could be used to build stronger, stiffer square foam-filled structures for lightweight vehicles, such as drones and other aircraft. They also said that the findings could be applied to other types of energy-efficient structures.

University of California - San Diego

Related Stress Articles:

Captive meerkats at risk of stress
Small groups of meerkats -- such as those commonly seen in zoos and safari parks -- are at greater risk of chronic stress, new research suggests.
Stress may protect -- at least in bacteria
Antibiotics harm bacteria and stress them. Trimethoprim, an antibiotic, inhibits the growth of the bacterium Escherichia coli and induces a stress response.
Some veggies each day keeps the stress blues away
Eating three to four servings of vegetables daily is associated with a lower incidence of psychological stress, new research by University of Sydney scholars reveals.
Prebiotics may help to cope with stress
Probiotics are well known to benefit digestive health, but prebiotics are less well understood.
Building stress-resistant memories
Though it's widely assumed that stress zaps a person's ability to recall memory, it doesn't have that effect when memory is tested immediately after a taxing event, and when subjects have engaged in a highly effective learning technique, a new study reports.
Stress during pregnancy
The environment the unborn child is exposed to inside the womb can have a major effect on her or his development and future health.
New insights into how the brain adapts to stress
New research led by the University of Bristol has found that genes in the brain that play a crucial role in behavioural adaptation to stressful challenges are controlled by epigenetic mechanisms.
Uncertainty can cause more stress than inevitable pain
Knowing that there is a small chance of getting a painful electric shock can lead to significantly more stress than knowing that you will definitely be shocked.
Stress could help activate brown fat
Mild stress stimulates the activity and heat production by brown fat associated with raised cortisol, according to a study published today in Experimental Physiology.
Experiencing major stress makes some older adults better able to handle daily stress
Dealing with a major stressful event appears to make some older adults better able to cope with the ups and downs of day-to-day stress.

Related Stress Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#532 A Class Conversation
This week we take a look at the sociology of class. What factors create and impact class? How do we try and study it? How does class play out differently in different countries like the US and the UK? How does it impact the political system? We talk with Daniel Laurison, Assistant Professor of Sociology at Swarthmore College and coauthor of the book "The Class Ceiling: Why it Pays to be Privileged", about class and its impacts on people and our systems.