복합전도성 충전재를 사용한 섬유강화 복합재료의 전자파 차폐 특성에 관한 연구

Abstract

Due to the rapid growth of the electrical and electronic devices, which emit electromagnetic energy in the same frequency bands used by other users, it becomes essential to limit and shield electronic equipment against all source of interference caused by all these electromagnetic energies. In recent years, plastic industries have been increasingly involved with electronic devices such as TVs, office automatic instruments, computers etc. Because of the need for these housing to attenuate electromagnetic interference(EMI) and radio frequency interference(RFI), the technique of imparting shielding to EMI transparent polymers has received a great deal of attention. The EMI is basically electrical in nature and is due to unwanted electromagnetic emission being either radicated or conducted. Metal is considered to be the most effective material for electromagnetic shielding, but it is expensive and heavy. On the other hand, the use of polymer for housing the electronic device is popular due to its light weight, flexibility and less cost to make. Nowadays, housing of most electronic appliances is in plastics for the advantages of not only high production, light weight and design freedom, but also being natural insulator and reflection and/or absorbing EMI free. The objective of this thesis is to investigate the influence of material composition and design on to the electromagnetic interference shielding characteristics. Several fiber reinforced composite specimens consisting of general copper meshes, fine copper meshes, aluminum films, glass fiber, carbon fiber and stainless fibers were manufactured to perform the electromagnetic interference shielding experiments. In order to soak(absorb) the specimen in electromagnetic fields, flanged coaxial transmission line sample holder was fabricated according to ASTM D 4935-89. Electromagnetic shielding effiency (EMSE) was measured quantitatively to examine the electromagnetic shielding characteristics of designed specimens. The range of frequency considered is 300 - 1500MHz. The result of electromagnetic interference shielding experiments showed that maximum EMSE value of specimens with general and fine copper meshes were 60dB at a frequency of 600 MHz and 70dB at a frequency of 1500 MHz, respectively. The maximum EMSE value of sandwich type specimen, which consist of both two skin sheet with stainless fibers and core with glass fibers, was 80dB at a frequency of 1500 MHz. From these results, it was noted that the sandwich type specimen consisting of skin sheets with stainless fibers and core with glass fibers has an excellent electromagnetic interference shielding characteristics in a high frequency range of electromagnetic wave.