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DuPont's commitment to the U.S. military market began in 1965 when Stephanie Kwolek, a DuPont research scientist, developed DuPont™ KEVLAR® brand fiber by spinning the fiber from liquid crystalline solutions. KEVLAR does not melt or shrink when exposed to heat and flame, and only carbonizes at very high temperatures (about 900°F/482°C in air). It’s also extremely resistant to cuts and a broad range of chemicals. Today, there are many exciting applications for KEVLAR, not only for the military, but for law enforcement personnel.
Law enforcement applications
Because law enforcement and correction officers around the world have no way of knowing the threat they could be walking into at any time, DuPont introduced a new, sophisticated body armor system in 2001 — the first flexible system to protect against knife and bullet threats.
Unlike the heavier, bulkier protective garments typically made of metal or ceramic, vests featuring KEVLAR® MTP™ technology are much lighter, concealable, flexible and comfortable for everyday wear. Body armor with this new technology provides protection to officers involved in a wide range of duties such as airport security and prisoner transport, or in quelling domestic disputes — where the type of weapon threat is always unpredictable.
The most recent innovation from KEVLAR is KEVLAR® Comfort XLT™. This ballistic technology helps provide protection without sacrificing comfort and the freedom of movement that law enforcement officers depend on to do their job. KEVLAR Comfort XLT is a patented technology that delivers significantly improved ballistic performance, which enables vest designs to be at least 25 percent lighter than current all-aramid fabric designs. That’s a big weight off any officer’s shoulders.
This article was written by DuPont.
In This Issue:
Plastics in aerospace:
Applications in government and military
Test your knowledge
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FERONYL, a Belgium-based manufacturer of seats for both military and commercial aircraft, chose VICTREX PEEK™ polymer to replace a magnesium alloy in a variety of seat components.
“PEEK meets the key requirements for outstanding mechanical strength and low flammability/low toxicity requirements in fire situations while delivering lower part weights than metal,” explains Chris Karas, general manager for Victrex Americas. “Seats in aircraft manufactured by companies such as Airbus, Eurocopter and Mirage have become complex assemblies. In addition to offering maximum comfort for passengers and crew, they must also provide long-term functional safety and passenger protection.”
Karas says, “An aircraft seat consists of numerous components that have traditionally been made from a magnesium alloy. However, crash tests have revealed that this material does not consistently ensure optimum elasticity. The lumbar support adjuster, for example, can show a permanent deflection after an impact without springing back as required.”
To provide the necessary long-term strength as well as creep and fatigue resistance, FERONYL chose a carbon fiber reinforced PEEK to mold both the lumbar support adjuster and the headrest. Because both the headrest holder and the seat belt guides do not require the same high level of mechanical strength and stiffness, FERONYL chose a glass reinforced grade of PEEK polymer.
In addition to providing superior mechanical performance in compliance with industry’s crash performance standards, seat components must also satisfy fire, smoke and toxicity requirements. “PEEK polymer has a UL-94 V-O flammability rating,” says Karas. “Plus, it is an inherently pure material which results in extremely low smoke and toxic gas emissions in fire situations. This performance advantage can significantly raise the chances of survival for passengers and crew in the event of a fire.”
First, military material standards serve to classify polymers based on their chemistry. For example, MIL-P-46183 covers Plastic Molding and Extrusion Material, Polyetheretherketone (PEEK). These specifications set allowable ranges for physical properties so engineers may design to the listed values without repeating basic standardized tests each time they specify PEEK.
Second, military detail standards provide specific instructions including allowable materials used in common parts such as connectors or fasteners. Therefore, they may actually state which resin types may be used and then refer to the appropriate military material standard for reference.
Walling says, “In general, military specifications help engineers avoid repeated tests and time-consuming material selection exercises leading to faster development cycles.”
This article was written by Victrex USA Inc.
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During the past 50 years, aeronautics technology has soared, with plastics playing a major role in both pragmatic improvements and dramatic advances. In aircraft, missiles, satellites and shuttles, plastics and plastic materials have enhanced and sped significant developments in military air power and space exploration and civilian air travel. For many of the same reasons that make them the materials of choice for such a variety of products that benefit our lives, plastics are the right stuff in aerospace.
From necessity to invention
During the war years, vinyl resins became a major substitute for rubber in Air Corps applications such as fuel-tank linings and fliers’ boots. Plastics also began to be appreciated as first-choice materials. Virtually transparent to electromagnetic waves, the plastic used in radomes, which housed radar installations, allowed the waves to pass through with minimal loss, maximizing transmission to night-flying bombers. Its introduction was hailed as having significantly advanced the technology of airborne radar.
The development of plastics that literally could “take the heat” associated with many aerospace applications and the launching of the U.S. space program spurred additional interest and extensive research in plastics for flight. Soon, plastic materials were common in aerospace for everything from interior trim in airplanes to nose cones for missiles. New words became familiar as “solid fuel boosters” on rockets and “ablative shields” for reentry came to rely on plastic materials. And when man landed on the moon, so did plastics.
In the 1970s, the oil crisis forced aerospace companies to design aircraft that used less fuel. This meant more efficient engines, improved aerodynamics and reduced aircraft weight. It also meant a role for plastics. Today, jet engine manufacturers increasingly use plastics for the same reasons: reliability, efficiency, fuel savings and improved performance.
The heavier the vehicle, the more fuel it takes to power it. For jetliners, the weight-to-fuel impact is tremendous. Just a one-pound reduction in weight translates into $1,000 in lifetime fuel savings. As composite engines can offer weight reductions of some 300 pounds over other materials, savings can be enormous.
Plastics also save fuel and money because their smooth contours improve aerodynamics. And plastics, which are less expensive to manufacture than heavier materials, produce parts that are more resistant to wear, require less upkeep and are easier to repair.
In the structures, interiors and functional parts of air and space craft, new applications continue to be found for plastic materials, and new plastic materials continue to be created to meet aerospace needs.
A show of force
Helicopters, which vibrate a great deal, can be called on to carry heavy payloads of equipment and personnel. The design of these vehicles calls for one set of materials that can compensate for the stresses caused by vibration and another that is stiff enough to hold up under a heavy payload. Plastics can do both, and more.
In military applications of rotor craft, plastics have been on the front lines of innovation. A new entry into the field, the prototype X-wing craft, sports sophisticated plastic-composite wings that act as a rotor during takeoff and landing but lock into a set position once in the air. The stresses inflicted on such a craft are numerous and varied. Only stiff yet light composites can stand up to them. Though developed for military purposes, the X-wing is believed to have potential as a commercial shuttle and to be jet-powered. Other modern military rotor vehicles — including vertical takeoff aircraft, a gunship and a minesweeper — rely heavily on plastic materials to accomplish their specialized tasks.
Plastics also are being, or are expected to be, used extensively for other innovative military craft. One material’s near invisibility to radar makes it indispensable for “stealth” aircraft, which designers hope to make undetectable to infrared and optical spotters. And plastic fibers could play a significant role in a proposed blimp that would warn naval forces of surface-skimming missiles. Such vehicles are also being considered for nonmilitary use in fields such as forestry and scientific observation.
Up to the challenge
New aircraft designs with rear-mounted engines will rely on plastics to take the stress and better allocate weight. Still lighter materials will increase the crafts’ capacities for more sophisticated avionics and other on-board systems. And plastics are expected to answer many of NASA’s calls for materials to create and perfect high-performance supersonic/hypersonic aircraft, nuclear space power systems and space stations.
This article was written by The Society of the Plastics Industry.
Many types of plastics are used in government and military applications — spanning a wide variety of uses for a long list of products — from items that need to provide safety and security (such as windows in buildings or for armored cars), to protective helmets and bullet-proof vests, to parts and components for military aircraft and vehicles.
Choosing the right plastic for an application is critical to the success of any design project, especially when lives are on the line. Certain plastics are chosen based on their characteristics, such as chemical or temperature resistance or high strength, and the design or engineering requirements for a project or product.
To help designers, engineers and specifiers understand the different characteristics of a variety of thermoplastic materials, the IAPD has developed the IAPD Thermoplastics Rectangle. This excellent reference tool is a must-have resource, and best of all, it’s free. On one side, there is a list of thermoplastics broken out by type and characteristics, and the other side includes commonly used thermoplastics in property comparison graphs. Download the rectangle now at www.iapd.org.
For more ideas of applications in the government and military sector, there are many articles online at www.theiapdmagazine.com. Just check "government and military " when you search the archives to find them. There are also many other free resources on the IAPD web site at www.iapd.org.
What do you know about plastic materials used for in government and military applications? (Answers are at www.iapd.org/popquiz.html.)
1. 'Which of the following materials has the best "continuous maximum operating temperature?"
2. Which of the following ratings would be best suited for a material if it needed protection from a .44 Magnum gun?
Your IAPD distributor is your choice in finding the right material for your application. Go to www.iapd.org to find a distributor in your area. You can search by company name, location or product category.
The IAPD Magazine web site at www.theiapdmagazine.com allows you to search by material, trade name and fabrication process. You can also search for fabrication capabilities.
Designing with Plastics is published by the International Association of Plastics Distribution. While every effort has been made for accuracy, IAPD encourages you to verify information with a plastics distributor to ensure you select the correct plastic products to meet your needs.