Mechanical-thermal Coupling Response Characteristics Of Porous Polymers

In the thesis, static and dyna mic mechanical properties under mult ip le factors and mechanical- ther mal coupling response characterist ics of the porous polymers are studied. The ma in research content is as fo llows,1. Based on the three- dimens iona l digita l speckle dyna mic deformat ion measureme nt and ana lys is techniques together w ith t he materia l testing syste m, quasi-static tens ile and compression tests of r igid polyuretha ne foam p last ics(RPUR) and silicone rubber foam(SR) are perfor med. The ther ma l and mechanica l behavior of RPUR and SR under var ious condit ions suc h as different stra in- rates, sampling direct ions and temperatures are obtained. Experimenta l results show that, under the invest igated condit io ns, the strain- rate effect and temperature effect in both tens ion and compression experiments of RPUR and SR are not quite obvio us. However, the temperature sensit ivit y in compression tests is stronger than that in tensile tests, the temperature sens it ivit y of high dens ity RPUR is stronger than that of low dens it y RPUR too, and the tensile strengt h and yield strength of RPUR and SR decrease w ith the increase of temperature. The specimens show anisotropic behavior in compression tests and in tens ile tests. Different specimen s izes of compression tests have negligib le influence on the mechanica l behavior of SR, but it has a significant impact on the mecha nical behavior of RPUR. The dama ge of SR specime ns in tensile tests is observed to be caused by the productio n of bubble ho le groove, but the fa ilure of compression specimens is due to the collapse of cells under externa l loading. O bvio us cracks in bubble ho les of RPUR are existed in tens ile tests, while compression specimens is due to the bubble ho le stress in t he defor mat ion and destroyed comp letely.2. Based on split Hopkinson pressure bar(SHPB), dyna mic mechanica l properties of RPUR and SR at high strain- rates are performed. It is found that the dyna mic mechanica l properties of RPUR and SR materia ls are different from their stat ic mechanic perfor mance, the strain- rate effect is not obvious w ithin the research scope of high strain- rates, and comparing t he static and dynamic cond it ions, later has obvious correlatio n wit h strain- rate.3. When the destruction of specimens occurs, the interna l temperature of specimens reaches highest. Temperature variat ions at different locatio ns of specimens are basica lly ident ica l, and the maximum te mperature rise of SR is sma ll. Therefore, exper iments conducted in this study can be regarded as isother mal tests, and the temperature rise of RPUR is larger, and the heat ing rate and the ma ximum te mperature rise increase w ith the incre ase of loading ve locity.