空气层匹配碳纤维吸波涂层的吸波性能

Absorbing Properties of Carbon Fiber Absorbing Coating Matched with Air Layer

目的探究空气层匹配厚度及碳纤维含量、长度对碳纤维吸波涂层吸波性能的影响。方法以短切碳纤维为吸收剂,水性聚氨酯为基体树脂,制备雷达吸波涂层。采用扫描电子显微镜和金相显微镜对短切碳纤维和涂层的微观形貌进行分析表征,将碳纤维涂层与空气层进行匹配,并采用矢量网络分析仪测试分析涂层的吸波性能。结果当空气匹配层厚度由1 mm逐渐增加到3.5 mm时,复合涂层的最大吸收峰由高频逐渐向低频移动。匹配厚度为3 mm时,反射率峰值最低(-41 d B)。匹配厚度为2.5 mm时,有效吸收频段(反射率<-10 d B)最宽,为8.6~18 GHz。随着碳纤维含量的增加,涂层的最大吸收峰频率均呈下降趋势,有效吸收频段向低频移动。碳纤维含量(质量分数)低于0.1%时,只有碳纤维长度达到3 mm,涂层才具备有效吸波性能。碳纤维含量为0.1%~0.2%,碳纤维长度为2 mm时,涂层吸波性能最好。碳纤维含量超出0.2%,碳纤维长度为1 mm时,涂层已经具备较好的吸波性能。结论通过调节空气层匹配厚度及碳纤维含量、长度,空气层匹配碳纤维吸波涂层在不同频段均能实现对电磁波的有效吸收。

The work aims to explore the effects of matching thickness as well as content and length of carbon fiber on ab- sorbing properties of carbon fiber absorbing coating. The radar absorbing coating was prepared with chopped carbon fiber as absorbent and waterborne polyurethane as matrix resin. Morphology of the chopped carbon fiber and the coating was analyzed and characterized by using scanning electron microscope （SEM） and metallurgical microscope. Carbon fiber coating was matched with air layer, and absorbing properties of the coating were tested by using vector network analyzer. As thickness of the air matching layer increased from 1 mm to 3.5 ram, the maximum absorption peak moved from high frequency to low frequen- cy. As the matching thickness was 3 nun, reflectivity peak was the lowest （-41 dB）. As the thickness was 2.5 mm, the effective absorption frequency （〈-10 dB） was the widest （8.6 ~ 18 GHz）. Maximum absorption peak frequency of the coating showed a decreasing trend as the carbon fiber content increased. When the carbon fiber content was lower than 0.1wt.%, the coating exhi-bited effective absorbing properties only when the carbon fiber length reached 3 mm. When the carbon fiber content was 0.1wt.% - 0.2wt.%, the absorbing property was the best when the carbon fiber length was 2 mm. When the carbon fiber content was over 0.2wt.%, the coating had better absorbing properties when the carbon fiber length was 1 mm. Effective absorbing properties of carbon fiber absorbing coating matched with air layer to electromagnetic wave can be achieved in several frequen- cy bands by adjusting matching thickness of air layer as well as content and length of carbon fiber.