Materials & Structures University Partnerships Offer Unique Force-Protection Opportunities and Directions
Military environments can be extremely challenging and often involve seemingly conflicting requirements, such as the need for materials that are both extremely lightweight and very, very strong. Taking nature as a guide, Raytheon and its university partners — the Institute for Soldier Nanotechnologies and the Ortiz Laboratory at MIT —have been studying nature to provide unique solutions to meet our customer's requirements and even go in new directions that may exceed customer expectations.
Although it is commonly acknowledged that nature inspires much of art, nature also has enormous potential to serve as inspiration for engineered processes, substances, devices and systems. Biological materials, such as musculoskeletal and exoskeletal tissues, have developed amazingly complex, hierarchical, heterogeneous nanostructures over millions of years of evolution in order to function properly under the mechanical loads they experience in their environment.
In addition to this, researchers have found that it is possible to amplify a material's properties in different ways just by creating structural differences at the nanoscale. Then, starting with more obtainable or perhaps even stronger materials, a better, lighter weight, more robust material or structure can be fabricated.
One example of such a natural material that has helped fabricate new forms of armor is nacre. Nacre — also known as mother-of-pearl — is essentially the strong part of a seashell and is primarily composed of calcium carbonate. Yet in a seashell the nacre has roughly 100X the fracture toughness and 5X the strength of most calcium carbonate samples. The secret to this strength is the multilayered structure, which the animal forms as the shell. These structural models have been used to fabricate similar mechanisms with stronger materials. Although research has yet to obtain the same strength amplification as that found in nature, researchers have demonstrated 10X increase in fracture toughness and 3X increase in strength in the same sample with no increase in density. This was accomplished merely through a nanoscale change in the material structure.
In an ongoing collaboration with the Institute for Soldier Nanotechnologies and the Ortiz Laboratory at MIT, Raytheon has been examining this and other natural systems. Another of the new systems being examined may help to save soldiers from improvised explosive device (IED) blast injuries. These injuries result from the after-affects of an explosion that causes enormous pressures to hit the soldier and compress the brain, producing in some cases damage that can never be repaired. These brain injuries can lead to life-long afflictions.
Nature has found a way to solve this problem, an approach which may prove useful to researchers attempting to mitigate this threat.
The bombardier beetle offers a unique unexplored opportunity — particularly for lightweight, soldier-protection applications such as blast shields — and a new direction in fire-retardant materials for first responders.
This type of beetle possesses a defense mechanism which involves ejecting a spray from the tip of the abdomen. The spray, which contains p-benzoquinones (a known chemical irritant) at elevated temperatures (100ºC), is ejected in a controlled direction and is accompanied by loud audible detonations. The quinones are generated explosively — completely within the interior of the beetle's body — by mixing two reactants: hydroquinones, hydrogen peroxide which are stored in two millimeter-sized reservoir chambers and then released by a valve into a reaction gland containing enzymes such as catalases and peroxidases, depending on the sub species of bombardier beetle. Oxygen is liberated (which acts as a propellant) from the hydrogen peroxide, and the hydroquinones are oxidized by the freed oxygen.
The reaction chamber and exit nozzles clearly have been designed over millions of years of evolution to protect the internal organs of the beetle from the resulting blast wave, heat and toxic chemicals during the defensive microexplosions. Currently, very little is known about the material structure and properties of this explosion-resistant pygidial chamber. The goal of the proposed research is to use new materials science and nanotechnological methodologies to investigate the detailed morphology and properties of this fascinating material. The fundamental materials design principles learned through this proposed research could likely be employed to develop a new class of fire-retardant materials, improved blast-protective equipment, and ultimately much lighter soldier loads.
The research in this area is ongoing. We are continuing to work with universities in an attempt to garner large, revolutionary breakthroughs in materials technology, not merely iterative performance increases. Engineers with ideas or thoughts relating to this ongoing research area are encouraged to contact either author with these for consideration.
In addition to this, researchers have found that it is possible to amplify a material's properties in different ways just by creating structural differences at the nanoscale. Then, starting with more obtainable or perhaps even stronger materials, a better, lighter weight, more robust material or structure can be fabricated.
