??? Although its products are under consideration for light tactical vehicle armor, Montrose, Colo.-based Polystrand’s ThermoBallistic sheet has been field-tested primarily in blast mitigation applications on military tenting and deployment shelters, in the fast growing market for armor in at-risk stationary structures, military and civilian.

??? Polystrand president Ed Pilpel believes his company’s ThermoBallistic composite sheets, which combine E-glass, AGY’s S-2 Glass, or aramid fibers in a PP or PE matrix, “are helping bring thermoplastic armor into the mainstream through lower cost and processing advantages.” He explains that the sheet material “is a finished composite when it goes out the door, unlike an A-staged thermoset prepreg, although the structural properties of the final panels may change when integrated into a total armor package under thermoforming or autoclave molding.” Polystrand’s composite sheet features 0°/90° cross plies and can be “compaction pressed” at only 100 psi in 40 to 60 percent less time than required by semi-rigid composites, with less waste and no outgassing of volatile organic compounds
Polystrand

??? “The low waste and no VOCs or ‘green’ aspect of thermoplastics are becoming more important to our military customers,” Pilpel claims. “When thermoset composites in blast shielding for deployment shelters are used in a desert environment, the release of VOCs can drive soldiers out of their tents,” Pilpel claims. That said, he admits that “thermoplastics offer a paradigm shift from 30 years of thermoset materials that are mil spec’d and well documented and understood. It will take some time to get a comparable database in place for thermoplastics.”

??? The University of Maine, in conjunction with the U.S. Army’s Natick Soldier Research, Development and Engineering Center (Natick, Mass.), has developed composite panels that form modular ballistic protected systems (MBPS) for temporary military shelters.， Drawing upon staff expertise at the University’s Advanced Engineering Wood Composites Center (AEWC), requirements for the MBPS have been established as high fragmentation capture and blast wave pressure survivability, rapid installation and set-up, light weight, and reusability.

??? AEWC’s answer turns to reinforced polymer skins over a wood core in panels approximately 4-ft wide by 7-ft long (1.2m by 2.1m) and weighing 90 lb/41 kg each. Fitted into a frame system, the panels line the outside of standard military tents. Initial panels were constructed in 2007 and subjected to ballistic blast overpressure testing. Test success has resulted in accelerated panel development and initiation of transition to the field.

??? “It is important to note that the MBPS （modular ballistic protected systems） is more than just a collection of panels,” states Dr. Habib Dagher, professor of civil and structural engineering at AEWC. “Each shelter application requires specific mounting and attachment hardware, blast-resistant doors and all shipping/installation support data, which affects overall design.” Panels are designed to absorb blast energy without breaking apart, yet feature support points as much as 8 ft/2.4m apart. “Hardware is designed to reduce peak loads on the shelter structure within the effects of blast energy.” AEWC continues efforts to reduce panel weight and installation time, and to work with panel manufacturers on optimizing specific production parameters.????

??? Another blast protection product developed with the U.S. Army is X-FLEX, a peel-and-stick blast-mitigation material from Berry Plastics Corp. (Evansville, Ind.). 　

??? Comprising aramid scrim fabric sandwiched between two layers of polyurethane film, the product features, on one side, an adhesive specially designed to adhere to construction surfaces, including brick and concrete.

??? X-FLEX came out of a cooperative R&D agreement with the Army Corps of Engineers’ Engineer Research and Development Center (ERDC, Champaign, Ill.). “It was critical that we develop a system that is easy to deploy without special equipment but provides threat-level protection in line with ERDC goals,” says Elizabeth Curran, director of engineering protective systems for Berry Plastics’ Tapes and Coatings division. X-FLEX, she says, meets those criteria: “Unlike other composite blast mitigation systems, X-FLEX is immediately effective and requires no drying time.”

??? Used primarily in existing buildings, X-FLEX is designed to keep a wall, or much of it, intact during a blast wave and then resist damage, post-blast, from fragmentation debris. Curran indicates that protection initiatives have become a major business segment for Berry Plastics, “and we have invested significantly to help address the many government-owned and private facilities that need blast mitigation systems.” Norplex-Micarta (Postville, Iowa) has been offering its glass/phenolic ShotBlocker sheet in rigid ballistic building panels since 1997 and for military vehicles in the past three years.

??? Rated to the highest-level DOS certification (Level 7), ShotBlocker is suitable for safe rooms, guard stations, and infrastructure wall and door structures. The company’s director of business development Alan Johnson says that ShotBlocker sheets incorporate glass fiber supplied by AGY and Owens-Corning Composite Materials LLC (Toledo, Ohio), using resins supplied by Ashland inc. (Dublin, Ohio) and Georgia-Pacific Chemicals LLC (Atlanta, Ga.). Over the past year, the company has delivered more than 1 million lb/453,590 kg of composite armor sheet, specifically designed to combat EFPs.

??? Other composite blast mitigation systems include BlastShield from BAE Systems (Houston, Texas), which features Spectra yarn in fixed interior window protection, and low-cost, pultruded glass/phenolic panels from KaZaK Composites (Woburn, Mass.).

??? KaZaK helped develop the High Expansion Ratio Shelter (HERS) temporary shelter system prototype for the U.S. Army, and is currently working with several U.S. Department of Defense agencies toward the use of its composite panels, not only in ground vehicles and structures but also in helicopter and ship protection.
Jerry Fanucci, KaZaK president, feels confident that “large pultruded panels are the key to the cost-effective implementation of composites in many military applications because larger panels mean fewer joints, less assembly cost and lighter weight.” The company has built a “superscale” pultruder that can manufacture composite sandwich panels greater than 10-ft/3.1m wide and of unlimited length.

??? Peace of mind

??? During an armed attack, the use of composites can be, literally, a matter of life or death. Although no material system can bring peace in today’s war zones, the protection that composites can provide against ballistic and blast threats is well proven. As these materials proliferate, more lives will be saved and the resulting armor technologies will afford, at least, greater peace of mind.
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