Fabrication Of Ferromagnetic Metal/PLA Absorbing Coating By FDM And Its Microwave Electromagnetic Properties

3D printing technology has the advantages of one-step forming,rapid forming and high-precision preparation of complex structures,etc.It is a very potential fabrication method for structural wave-absorbing coatings.Ferromagnetic metals as electromagnetic wave absorbers have the advantages of high saturation magnetization,high cut-off frequency,high magnetic loss,good temperature stability and easy access.In this paper,the variation law of electromagnetic parameters of Co and FeSi ferromagnetic metals is studied.A electromagnetic parameter prediction model using BP neural network is realized and a wide-band electromagnetic wave ansorbing coating is designed In addition,the coaxial test samples and the large size wave absorbing coating were successfully prepared by FDM,using ferromagnetic metal/PLA wire,and the electromagnetic and wave absorbing properties were tested.The BP neural network optimized by genetic algorithm is used to predict the electromagnetic parameters.The generalization ability of the model is good,and the mean square error of the predicted results is 0.001.At the same time,the electromagnetic parameters and coating thickness of the coating were optimized by using genetic algorithm,and the designed double-layer coating could absorb more than 90% of the electromagnetic wave in S,X and Ku bands with the total coating thickness of 6.5 mm,and the effective absorption bandwidth reached 11.0 GHz.The ferromagnetic metal/PLA composite wire with the highest filling rate of60 wt.% was prepared by ball milling and melting extrusion.Coaxial ring samples formed by FDM can be directly used in coaxial fixture testing of vector network analyzer for electromagnetic parameters.The results are in good agreement with those of the ferromagnetic metal/paraffin coaxial samples pressed by the die.The absorption coating with the size of 180 mm×180 mm was successfully prepared by fused deposition modeling.The actual test results of reflection loss in microwave anechoic chamber showed that the effective absorption frequency band of the coating with the thickness of 2.5 mm covered 11.2-16.7 GHz,and the effective absorption frequency band of the coating with the thickness of 1.5 mm covered 14.7-18 GHz,These experimental results are verified by theoretical calculation.The fabrication method of absorbing coating by FDM has the advantages of one-step forming,simple operation and absorbing structure design.