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Investigations on the Broadband Shielding Effectiveness of Metallized Glass Fiber

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Final rept. for fiscal year 96

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Metallized glass fiber MGF is a glass fiber substrate with a metal coating that can be used to improve the electrical properties of reinforced composites. The material considered here RoMHOglasTrademark-metallized glass conductive fibers produced by Lundy Technical Center, Pompano Beach, Florida is an E-glass fiber metallized with Al and processed into a nonwoven mat. When formed into a mat, the MGFs lead to an effective sample conductivity, sigma eff, which is the parameter of interest for electromagnetic shielding in the RF region. Experimental results are presented that show that sigma eff is dependent on the resin and curing process used to produce the MGF samples. The sample conductivity was optimized using polyester resin and vacuum bagging techniques. The lessons learned were used to construct an MGF shielded Army tactical shelter size enclosure having no apertures or penetrations other than the door opening. We applied two layers of the MGF mat to the interior surfaces of a plywood, full-scale model of an Army tactical shelter. Using overlapping seams, we secured the MGF layers to the plywood walls and sprayed them with polyester resin. A vacuum bag was filled to the interior and exterior of the shelter model. A vacuum was applied to compress the two layers of MGF mat and remove excess resin. A metal door with an eight cleat clamping arrangement and an electromagnetic interference gasket was used to provide a continuously shielded enclosure. This shielded enclosure was then tested according to IEEE-STD-299-1991, with some modifications, at frequencies up to 17 GHz. The results are presented as recommended by the test standard and indicate that compressed MGF mat can provide roughly 60 dB of attenuation to a distant source, but very little shielding below 10 MHz.

Subject Categories:

  • Electromagnetic Shielding
  • Laminates and Composite Materials
  • Structural Engineering and Building Technology

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