Sound Insulation And Mechanical Properties Of Composite Sandwich Panels For High-speed Train Floors

It becomes a new norm to frequent travel and to commute between cities in today's fast facing society.High-speed trains are effective in meeting this ever growing demand.The rapid development of high-speed trains greatly shortens travel time,but high noise comes with high speed.Therefore,it is necessary to construct the high-speed trains with materials which have both lightweight and better sound proof.It have important practical significance for sustainable and stable development.In this paper takes the floor of high-speed train as the object of study.The standard floor(current 350km/h high speed train floor)was used as the reference.To achieve weight reduction,composite panels having sandwich structures were selected as the floor material.Nomex honeycomb core was selected for its low density and high stiffness,a new type of skin made out of polyphenylene sulfone(PPS)non-woven prepreg,together with fiberglass and carbon fiber prepreg were used as the skin materials.The sandwich panels were fabricated by compression molding,cut and tested for their sound insulation,flexure strength and compressive strength.The first series of sandwich panels were made using Nomex honeycomb cores having different cell size and density,together with a selected type of prepreg material.The results showed that the thickness,density and skin material of the prepreg all had a certain effect on the sound proof performance of the sandwich panels.When the core thickness and density increased,the panels' sound proof performance improved.Furthermore,the PPS non-woven skin was found to be the best sound proofing amongst the skin materials.On the other hand,the cell length of the honeycomb core had little effect on sound insulation.When the panels used PPS non-woven prepreg,together with glass fiber prepreg or carbon fiber prepreg as hybrid skin,the results were quite consistent,showing that PPS non-woven prepreg mixed with a layer of carbon fiber or fiberglass prepreg as the inner or outer layers of the hybrid skin had little effect on the sound insulation performance of the sandwich panels.In the second series,the sandwich panels were made by different honeycomb cores with a single type of prepreg material.Their flexure properties and compressive strength were tested.The results showed that the thickness,density,cell length of the honeycomb core,together with skin types,all had some effects on flexure properties.When the core thickness and density increased,while cell length decreased,the flexural stiffness of the sandwich panel increased.The carbon fiber skin was the best for achieving high flexural properties.The factors,namely core thickness,density and cell length,had different effects on the compressive modulus of the sandwich panels.Increasing compressive strength was found with increasing core density and thickness,but with decreasing cell length.The skin material had almost no effect on the panels' compressive properties.Finally,PPS non-woven prepreg and carbon fiber prepreg were used as mixed skin materials and honeycomb core having favorable performances,i.e.large thickness,high density,and low cell length.In addition,hollow glass spheres were added to improve the sound insulation.The sandwich panel thus produced was tested for sound insulation,flexural,and compressive tests.The results showed that adding hollow glass spheres,at the loading level of 5wt% based on prepreg resin content,showed improved the sound insulation of 5-8 d B between 500-1300 Hz,compared to that of the standard floor panels.While,while in the frequency range of 500-1300 Hz,the composite floor panels performed equally to the standard floor panel,and was slightly inferior to the standard floor panels between 1300-2500 Hz.In terms of mechanical properties,the flexural stiffness and the compressive strength of the composite panel were slightly better than that of the standard panel.The most significant result was that the composite floor panels was 30% lighter than the standard panels,making them a strong candidate for higher speed train floors,with both improved weight reduction and sound proofing.