Absorbing Of Pan-based Fibers And Absorbing Structure

The performance and preparation of plyacylonitrile(PAN) base microwave absorbing fiber and structure was researched in this paper, and microwave absorbing structure with good performance was made after optimization design.PAN preoxidized fiber was heat-treated at 550℃ , 600℃ and 650℃ to obtain microwave absorbing fibers. When the heat-treatment temperature is increased, the dielectric constant of the microwave absorbing fiber is increased too. When the heat-treatment temperature is 650 C,the tangent of dielectric loss angle of the fiber approachs to 1, and the frequency response characteristic is fine from 2GHz to 18GHz . In the heat-treatment ambience, the vapor is the most important factor, and reducing the vapor can make the electromagnetic properties more steady.3 kinds of composites with different fiber volume fraction were made with paraffin and microwave absorbing short cut fiber, and their dielectric constants were measured. Research shows that the dielectric constants fit empirical formula . For the real part of dielectric constants, n is 0.936, and for theimaginary part, n is 1.506.The microwave absobing fabric/resin composite materials were made with hand laying-up or mould pressing, and their dielectric constants were measured. Fabric multi-layer model was created, and equivalent thickness of fabric layer in this model was worked out. For hand laying-up the equivalent thickness was 0.65mm, and for mould pressing the equivalent thickness was 0.56mm.The short cut fiber coat was optimization designed. When the coat thickness is 2mm, the bandwidth less than -10dB can reach 6GHz.6 pieces of fabric microwave absorbing material were made, and their reflectivities were measured. Their reflectivities were calculated according to the fabric multi-layer model also, and compared with measured value. The result shows that they fit into each other well.The fabric microwave absrobing material is optimization designed.As a result, it is favourable that the count of layers is 4. The thickness of hand laying-up product is 5.2mm, and the bandwidth less than -10dB is 9.2GHz. The thickness of mould pressing product is 3.2mm, and the bandwidth less than- 10 dB is 10 GHz.The mechanical properties of microwave absrobing material are measured. The bending strength of hand laying-up product is 77MPa, and the bending modulus is 4.98GPa. The bending strength of mould pressing product is 173MPa, and the bending modulus is 12.53GPa.