Preparation Of Protective Materials Based On Highly Dispersive Shear-thickening Liquid And Simulation Of Electromagnetic Wave Absorption Performance

With the continuous development of weapons and equipment,it is of great significance to develop protective materials with high protection,light weight and multi-functionality.Shear thickening fluid(STF)is liquid without being impacted.Once it is severely impacted,shear thickening will occur and harden rapidly,thus playing a protective role.In this paper,gas-phase SiO₂nanoparticles with a specific surface area of 200 m~2/g and a particle size of 12 nm were used as the dispersed phase,Preparation of STF with polyethylene glycol(PEG 400)as dispersion medium,and ultra-high molecular weight polyethylene fiber(UHMWPEF)was used as the reinforcement phase.Oxygen resin composites were used as skins to prepare liquid/solid dual-phase composite protective materials,which were composited with Fe₃O₄@rGO particles and STF to endow the protective materials with electric wave absorption properties,and the related electromagnetic wave absorption properties were studied.The specific content and main results are as follows:(1)According to XRD and FT-IR,STF was successfully prepared through the bonding between the terminal hydroxyl groups of PEG 400 and the silanol groups on the surface of SiO₂.The effects of different preparation processes and SiO₂ filling amount on the steady-state rheological properties of STF were studied according to magnetorheology.At the same time,the particle size and dispersion of nanoparticles in STF were studied by DLS and SEM.The research results show that:(1)The synthesized STF is composed of high-purity amorphous structure gas-phase SiO₂nanoparticles and PEG 400.Due to the intermolecular dehydration of gas-phase SiO₂ and PEG 400,a new-Si-O-C-bond is formed.The form of solvated layer was adsorbed on the surface of SiO₂,which made SiO₂ stably dispersed in PEG 400.(2)For a system with a larger amount of SiO₂,the SiO₂ agglomerates are more likely to collide,so the critical shear rate is lower,and the particle clusters formed by the agglomerates are larger and better to hinder the fluid movement,resulting in an increase in viscosity.(3)STF prepared by different processes has different dispersibility,and good dispersibility can make the particle size distribution uniform,thereby reducing the critical shear rate.The STF with SiO₂ filling content of 20%prepared by mechanical stirring-ultrasonic combined treatment has the best dispersibility,the peak viscosity is 1058.9 Pa·s,and the critical shear rate is 3.49 s^-1.It can meet the requirements of subsequent liquid protective materials for STF rheological properties.(2)On the basis of the optimal STF preparation process,STF infiltrated fibers are prepared by compounding with ultra-high molecular weight polyethylene fibers,and multi-layer STF infiltrated fibers are edge-sealed to prepare flexible liquid protective materials,and glass fiber skins are used to prepare"mouth-shaped"hard The impact resistance of the two protective materials was studied by a drop weight tester.The research results show that:(1)For liquid protective materials,the impact resistance of the liquid protective material composed of 2 layers of STF-impregnated fibers is better than that of the 8-layer pure fiber protective material,and the effect of STF is significantly weakened with the increase of the number of layers.(2)For the flexible liquid protective material,the 2-layer flexible liquid protective material has the best STF enhancement effect,the energy absorption is 11.62 J,and the STF enhancement factor is20.04.(3)Among the hard protective materials,the shear thinning property has little effect on the impact resistance of the protective material,while the shear thickening property can greatly improve its impact resistance,indicating whether STF shears in the hard protective material.Thickening will not cause the impact resistance of the protective material to decrease.The 4-layer hard protective material has the best STF enhancement effect,and the energy absorption is 47.298 J,and the energy absorption of the rigid composite material composed of pure fiber is increased by 4.271 times.The structures of the two protective materials have excellent impact resistance,which meets the requirements for the structure in the subsequent microwave absorption simulation of functionalized protective composite materials.(3)Fe₃O₄@rGO absorbing particles were used to blend with the liquid protective material,and the electromagnetic parameters of the functionalized liquid protective material were extracted by the coaxial method,and the CST microwave studio was used to conduct simulation experiments to optimize the structural parameters and study its related absorption.Wave properties and laws and put forward the corresponding mechanism explanation.The research results show that:(1)The optimal number of layers of the two functionalized protective materials is 9 layers,and the effective absorption frequency of the flexible functionalized protective material is 5.35-7.79 GHz,the effective absorption bandwidth reaches 2.44 GHz,and the minimum reflection loss is at 6.74 GHz Reaching-20.60 d B,the effective absorption frequency of the hard functionalized protective material is 3.94-5.68 GHz and 14.94-17.52 GHz,the effective absorption bandwidth reaches 4.32 GHz,and the minimum reflection loss reaches-26.73 d B at 15.96 GHz.(2)The loss form of Fe₃O₄@rGO particle functionalized flexible protective material is mainly electrical loss.(3)There is a standing wave phenomenon in functionalized protective materials.,which indicated that the ₄~1?resonance was generated at the absorption frequency,and the standing wave phenomenon of the hard functionalized protective materials was more obvious.(4)It can be seen from the Smith chart that the skin also has the effect of improving impedance matching.