Artificial fiber could replace spider silk in composites engineering research

  Researchers at the University of Nebraska at Lincoln could have found an innovative engineering solution to one of the trickier problems in materials science – making a structural fiber that is both strong enough to bear heavy loads and…

 

Researchers at the University of Nebraska at Lincoln could have found an innovative engineering solution to one of the trickier problems in materials science – making a structural fiber that is both strong enough to bear heavy loads and tough enough not to break under duress.

When manufacturers need a solid component, generally today, they rely on steel to provide the best mix of cost and strength. The metal is even used in some cases that require flexibility, weaving it into cords.But when weight and flexibility are as important as strength – as in many composite materials used in manufacturing or in items such as bulletproof vests – steel and other metals simply cannot provide the necessary attributes.Leading candidate

In years past, materials scientists identified a promising candidate in spider silk, one of the best mixtures of strength and toughness in the natural world. Silkworms have been domesticated in Asia for thousands of years, but spider silk represents an even greater opportunity because of its much greater strength and toughness. Strength in this case refers the ability of a material to retain its shape and carry heavy loads, while toughness represents the ability to deform rather than breaking.The difficulty comes in that spiders are not easy animals to domesticate like silkworms. Their aggressive and territorial nature makes them largely impossible to keep in the same enclosure, and collecting their silk is often more difficult.A variety of different projects have sought to replicate these immensely useful fibers without the actual difficulty of dealing with the spiders themselves. Engineering research on the subject has ranged everywhere from using modified silkworms to bacteria to the seemingly outlandish idea of goats.Cutting out biology
In many of these cases, the researchers have proven reasonably successful and spider silk is currently manufactured through bioengineered methods in some significant quantities.At the University of Nebraska, however, a team led by professor of mechanical and materials engineering Yuris Dzenis hoped to find a material that could fill the role of these spider silks without needing to rely on bio-based production.To accomplish this, the researchers used a technique known as electrospinning, which electrically charges a liquid base in a way that draws out an extremely fine stream of the substance. This stream can be dried and formed into a solid thread only nanometers in thickness.The material itself is known as polyacrilonitrile, a substance similar in some respects to acrylic and already in regular use. However, Dzenis and his team discovered that dramatically reducing the size of the threads could help to create a material that was both incredibly strong and remarkably tough. The first part was expected, as it is common for such thinly-spun threads to feature high proportional strength, but usually toughness and strength are somewhat mutually exclusive, in almost all areas of materials science.The current theory is that the extremely fine threads are less crystalline, with more areas that allow for relatively free movement of molecules, making them better able to withstand external pressures.“Our discovery adds a new material class to the very select current family of materials with demonstrated simultaneously high strength and toughness,” Dzenis said in a statement. “Whatever is made of composites can benefit from our nanofibers.”The research was funded at least in part by both the Air Force and the U.S. Army, both of which have a major stake in creating more resilient composite materials. Threads such as this can be used to create cheaper, lighter and more reliable bulletproof vests, while airplanes are highly reliant on composites to make airplanes that can suffer damage without experiencing a catastrophic failure.
Read more like this