| Foam metal has the characteristics of sound absorption and noise reduction,and has broad application prospects in the control of noise pollution in environ-mental protection,transportation,military and other fields.But the low porosity and single pore structure of foam metal has low sound absorption property and the high porosity of foam metal has low strength,which can not meet the needs of noise control fields.By improving porosity and making periodical pore structure of porous foam metal,we can optimize the sound absorption properties of materials.Moreover,compositing fiber can make up for the decrease of the strength caused by the increase of porosity,ob-taining high sound absorption and high strength foam metal.In this paper,high porosity,layered periodic pore structure Al-Si12 alloy foam(abbreviation HLA alloy foam)and high porosity,layered periodic Al-Si12 / stainless steel fiber composite foam(abbreviation HLAS composite foam)was prepared by infiltration casting method with Al-Si12 alloy as raw material.The mechanical properties,acoustic properties,preparation,and pore structure characterization of high porosity layered Al-Si12 / stainless steel fiber composite foam were studied.The main results of this paper are as follows:(1)The HLAS composite foam has a porosity of 73%~86%,a size of Ф30×30 mm,including 4 layers of periodic structure for each layer of 7.5 mm(7.5(0.5+0.2)mm+7.5(0.8+0.35)mm+7.5(0.5+0.2)mm+7.5(0.8+0.35)mm).(2)The test results of compression property of HLA S composite foams with different porosity show that the compressive yield strength of HLAS composite foam decreases greatly with increasing porosity.The porosity of HLAS composite foam increases from 70.25% to 86.04%,the compressive yield strength decrea ses from 18.83 MPa to 2.51 MPa.Stainless steel fibers are embedded in the alloy matrix by being surrounded or half-enclosed by the cell walls,passing through the holes,protruding from the holes,can withstand partial external pressure.With the increase of fiber content,the compressive yield strength of the HLAS composite foam increases first and then decreases.When the porosity was 81%,the fiber diameter was 0.10 mm,and the fiber content increases from 0vol.% to 5vol.%,the compressive yield strength increased from 5.09 MPa to 7.58 MPa.When it increased to 8 vol.%,the compressive yield strength decreased to 4.99 MPa.When the indenter is applied to different apertures,the material has the same mechanical properties.(3)The results of sound absorption property tests of HLAS composite foams with different porosities at 800~6300 Hz show that the sound absorption coefficient of HLAS composite foams increases first and then decreases with the increase of porosity.The porosity increases from 70.25% to 81.60% and finally increases to 86.04%,the average sound absorption coefficient of the HLAS composite foam increases from 0.68 to 0.81 and finally decreases to 0.68.Stainless steel fibers staggering in the holes,hindering the propagation of acoustic wav es in the HLAS composite foam.With the increase of fiber content,the average sound absorption coefficient of HLAS composite foam first increases and then decreases.With a porosity of 82%,a fiber diameter of 0.10 mm,and a fiber content of 0vol.% to 5vo l.%,the average sound absorption coefficient increases from 0.75 to 0.8,and finally increases to 8vol.%,the average sound absorption coefficient decreases to 0.77.When the sound waves are incident from the large aperture surface,the material has bette r sound absorption properties.(4)The sound absorption mechanism of the HLAS composite foam was analyzed: The depletion of the acoustic wave in the fiber composite foam mainly depends on the pore size,porosity,hole bending and surface roughness of the c omposite foam.With the increase of porosity,the decrease of average pore size,the embedding of fibers and the periodicity of pore structure,the flow resistance of the material increases and the sound absorption property increases. |
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