Study On Preparation And Properties Of Polyurethane Wave Absorbing Composites

In 21 st century,people live on an earth that full of electromagnetic waves,facing the problem of electromagnetic wave pollution.Meanwhile,in military field,people have to reduce the reflection of electromagnetic wave to decrease the possibility of being dected.Therefore,the study of wave absorbing materials has been one of the focuses in the study of composite materials for many years.In this paper,polyurethane wave absorbing composite material was made by using rigid polyurethane foam as matrix,and using carbon fiber and micro Fe,Co,Ni powder as absorbers with a mass fraction of 1~9%.The sample's fireretardant properties,thermal stability,and mechanical properties by using limiting oxygen index instrument,thermogravimetric analyzer,universal testing machine,and choose one of the materials that has the best properties to make 100 times bigger samples.The reflectivity characteristics of these enlarged samples are analyzed by NRL-arc method.The result shows:(1)The limit oxygen index of the samples increases with the increase of carbon fiber content,and reached it's maximum of 24.7% when the content of carbon fiber was 9%.On the other hand,samples' limit oxygen index decreases with the increase of micro metal powder content.(2)The four kinds of wave absorber have little improvement on the thermal stability of polyurethane matrix,but the difference is not markable.(3)Carbon fiber has the best effect on mechanical properties of polyurethane.The compressive strength of the samples increases with the increase of carbon fiber content,and reached it's maximum of 1103.9kPa when the content of carbon fiber was 9%.(4)The sample had it's best wave absorbing properties when the content of carbon fiber was 1%,and would showed the peak value of-30.56 dB at 12.01 GHz,and band width under-10 dB and-20 dB were 14.87 GHz and 5.06 GHz.