Effects of strain-rate and temperature on mechanical behavior of polyimide foam in compression

Polymeric materials are now major materials used in various situations. However, most polymers are usually unsuitable for use in high temperature environments because of low glass transition temperature. In polymers, however, polyimide is one of polymers having relatively higher glass transition temperature and high strength. This means that the mechanical property of polyimide has been said not to be changed very much by temperature. Therefore, polyimide foam is expected to show good mechanical performance over wide temperature range. In order to increase the use of a polyimide foam in industrial applications, it is necessary to know its deformation behavior in wide range of strain rates and temperature. In this study, a series of compression tests at various strain rates, from 10-3 to 103 s-1 were carried out in order to examine the effect of strain rate on the compressive properties of polyimide foam. It was found that the flow stress of polyimide foam increased dramatically at dynamic strain rates. The effect of ambient temperature on the properties of polyimide foam was also investigated at temperature from -190 °C to 270 °C. The flow stress decreased with increasing temperature in the range from room temperature to 270 °C. At -190 °C, the deformation behavior of polyimide foam changed to be brittle