| Aramid honeycomb core(ARHC)is a lightweight structural core material with flame retardancy,high temperature resistance and electrical insulation,high specific strength and specific stiffness,which is widely used in many fields.However,the hollow structure of ARHC causes serious defects in sound absorption and heat insulation,making it can't be used as a multifunctional structural material.In order to solve the above problems,this paper proposed the idea of filling the ARHC core grid with polyimide foam(PIF)which has excellent sound absorption and heat insulation performance to greatly improve the performance of ARHC.Using PIF one-step preparation technology,the one-step PIF filled honeycomb core(ARHC/PIF)composite material was successfully prepared with sound absorption and heat insulation performance far superior to ARHC.This article mainly carried out the construction work of PIF with different pore structure,different density and different hollow glass beads(HGB)content in ARHC,and studied the overall sound absorption,heat insulation and mechanical properties of ARHC/PIF composites.By adjusting the foaming slurry quality and the volume ratio(M/V)of the closed mold for molding,the density of the PIF filled in the core grid and the pore structure parameters were greatly adjusted.As the density of the composite core material gradually increased,the average cell size of the PIF filled in the core grid gradually decreased,but the open cell ratio presented a trend of first increasing and then decreasing;the thermal conductivity of ARHC/PIF had gradually increased,and the lowest value reached 0.048 W/(m·K),which was reduced by about 28% compared with ARHC materials;compression performance test showed that ARHC and PIF had an obvious synergy in mechanical properties.The filling of PIF greatly improved the sound absorption performance of the material.With the increase of PIF density,ARHC/PIF can greatly improve the absorption effect of sound waves below 800 Hz while keeping the sound absorption behavior in the middle and high frequency range the same basically;however,when the density of PIF reached 220 kg/m~3 or more,the effect of improving the sound absorption behavior of the composite material was greatly weakened due to the drastic change of the cell structure.In order to ensure the lightweight properties and thermal insulation effect of the composite core material,according to the ARHC/PIF-1 preparation process,the method of adjusting the amount of foaming agent and surfactant in the slurry was selected to adjust the PIF pore structure parameters,and the optimal results were screened.The results showed that the pore structure of PIF in ARHC/PIF-6 was the most uniform,with an open cell ratio of36.7% and an average cell size as low as 0.2 mm;the sound absorption coefficient was the highest in the middle and high frequency range,and the peak value reached 0.9,and the average sound absorption coefficient and NRC reached 0.78 and 0.58 respectively;the thermal conductivity remained at 0.049 W/(m·K).HGB were selected as the sound-absorbing and heat-insulating filler,and the influence of HGB on the sound-absorbing and heat-insulating properties of ARHC/PIF materials was studied,and the optimal results were screened.With the increase of the amount of HGB in the foamed slurry,the open cell ratio and average cell size of PIF showed a trend of first increasing and then decreasing and first decreasing and then increasing,and the thermal conductivity was maintained at 0.046?0.049 W/(m·K).The results showed that when the amount of HGB was 20 wt%,the open cell ratio of ARHC/PIF-HGB-2 reached 45%,the average cell size was 183 ?m,and the average sound absorption coefficient and NRC reached0.88 and 0.71,respectively. |
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