ULTRA-LIGHTWEIGHT COMPOSITE-MATERIALS FOR EMI SHIELDING

Shielding against electromagnetic interference (EMI) is critical in ma ny aerospace and terrestrial applications. Conventional bulk metallic materials currently used for EMI shielding can incur large weight pena lties. To overcome such weight penalties, ultra-lightweight composite materials utilizing conductive fillers ranging from carbon microballoo ns to silver-coated ceramic microballoons are proposed. The crucial re quirement for EMI shielding is electrical conductivity of the constitu ent materials, while the hollow microballoon geometry is utilized to y ield low weight. Methods of processing, and composition effects are ex amined and these results are compared to the effectiveness of varying the conductive microballoon material. Three different test techniques, including X-band reflection, microwave anechoic chamber relative shie lding effectiveness, and coaxial transmission testing, are used to qua ntify, the shielding performance of these materials over a wide range of frequencies. The resulting ultra-lightweight materials, developed f or EMI shielding, can be tailored through the application of the under standing of the relative effects of variables such as microballoon mat erial, volume fraction, and distribution. Initial experimental results reveal that these tailored ultra-lightweight composite materials yiel d shielding effectiveness at least equal to traditional aluminum shiel ding at only a small fraction of the weight.