| The electromagnetic transmission performance of carbon/epoxy 2.5D composites with different fiber volume fraction and fiber types and weaving structure were researched by the Agilent ZNB40 vector network analyzer using free-space method. The scattering parameters, the electromagnetic wave reflection ER, wave absorbtion EA, multiple reflection EM and reflectivity Loss R were calculated. The calculation results of S scattering parameter show that:The wave absorption is the main form in the process of electromagnetic wave transmission and the Ku-band is the optimal absorption band (12-18GHz). In the Ku-band (12-18GHz), as the fiber volume fraction increases from 44.8% to 61.2%, the absolute value of reflection loss peak has a reduction of 5.46dB, with the loss peak moves to the low frequency. While other variables being constant, with the carbon fiber type changes (T800-6K, Toray T300-6K, domestic T800-6K, domestic T800-12K), the absolute value of reflection loss peak of composites in the Ku-band (12-18GHz) are-36.30dB,-36.21dB,-34.35dB, and-39.43dB, which indicate that fiber types have little influences on the electromagnetic wave absorption properties. The effect of three-dimensional orthogonal woven, warp layers to enhance the angle interlock and angle interlock interlocking structure of the carbon fiber composite materials on electromagnetic wave transmission performance is not obvious, those three structures have reached the minimum reflection losses-43.5185dB,-35.5471 dB,-40.0321dB at the frequency of 15.6GHz, from the analysis of reflection loss peak, three-dimensional orthogonal woven has the best performance on electromagnetic wave absorbing, while angle interlock interlocking structure is relatively worst. But it can be concluded from the reflection loss overall graphics that structure of the composite material has a certain influence on the electromagnetic wave transmission performance, but the effect is not obvious.
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