본 연구에서는 탄소섬유강화 복합재의 전자기파 차폐 특성에 관해 연구하였다. 탄소섬유-에폭시 프리프레그 135플라이를 몰더에 적층한 후 가열-가압법에 의해 성형하여 차폐시료제작에 사용하였다. 이때 섬유는 24 ton/㎟, 36 ton/㎟의 탄성률을 갖는 두 종류를 사용하였으며, 0, 30, 60, 90도의 배향각을 고려하여 시편을 절단하였다. 주파수 분산실험은 1㎓에서 25㎓까지 회로망 분석기를 이용하여 수행하였다. 그 결과 배향각도가 커지면서 투과 손실량이 적었으며, 특히 90도의 배향각에서는 주파수가 높아지면서 0.1%만이 투과될 뿐이었다(99.9% 차폐를 의미함). 또한 기존의 등방성 재료에서의 체적저항과 차폐효과의 반비례 관계는 본 섬유강화 복합재료에서는 성립하지 않았다. 즉 동일 구성(섬유함량, 섬유등급 같음)의 재료에서 섬유의 배향에 따라 차폐효과는 크게 다른 것으로 관측되었다. 따라서 섬유강화 차폐재료 제조에서는 성형체의 강도뿐만 아니라 효과적인 차폐 역할을 위해서는 섬유의 배향에 대한 영향을 크게 고려해야 할 것으로 판단된다.

In this research, the microwave shielding characteristics of the carbon fiber reinforced composites were studied. Carbon fiber-epoxy prepregs of 135 plies were laminated, hot-pressed and prepared for measuring the shielding effectiveness. Two kinds of carbon fibers with the modulus of 24 and 36ton/mm² were used and the fiber orientation angles of the composite sample were 0, 30, 60 and 90 degree, respectively. The experiments were carried out by using the network analyzer(HP 8510) in the corresponding frequency ranges of 1GHz-25GHz. As a result, the transmission loss was decreased as increase in the fiber orientation angle for the direction of the microwave. Especially, the composite sample with the fiber orientation of 90 degree shielded the microwave up to 99.9%(0.1% is only transmission power). Also the inverse proportional relationship between volume resistivity and shielding effectiveness in the typical isotropic materials were not established in the fibrous composite materials of this research. That is, in spite of the same constituent materials(such as fiber content, fiber grade), the shielding effectiveness as to the fiber orientation was revealed as a great differentiation. So, on preparing the fiber reinforced composites, the controlling of the fiber orientation within the composites must be considered for the shielding effectiveness as well as the mechanical properties of the fibrous composites.

Carbon Fiber Reflection Loss Transmission Loss Microwave Shielding Shielding Effectiveness Fiber Orientation

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