The mechanical properties of polymers, particularly as a function of temperature and strain rate, are key for implementation of these materials in design. In this paper, the compressive response of low density polyethylene (LDPE) was investigated across a range of strain rates and temperatures. The mechanical response was found to be temperature and strain rate dependent, showing an increase in stress with increasing strain rate or decreasing temperature. A single linear dependence was observed for flow stress on temperature and log strain rate over the full range of conditions investigated. The temperature and strain rate data were mapped using the method developed by Siviour et al. based on time-temperature superposition using a single mapping parameter indicating that there are no phase transitions over the rates and temperatures investigated. Taylor impact experiments were conducted showing a double deformation zone and yield strength measurements in agreement with compression experiments.

The procedure for determining quasi-static fracture toughness of ceramics has been standardized. To expand the loading rate into the dynamic region, the dynamic equilibrium over the entire specimen needs to be satisfied to interpret the crack tip loading state with the far-field loading conditions. Furthermore, to determine the loading-rate effects, the loading rate at the crack tip should be nearly constant during an experiment. A new fourpoint bending experimental technique, based on a split Hopkinson pressure bar, has been developed to determine the dynamic fracture toughness of ceramics at high rates under valid conditions, which is demonstrated through the determination of the dynamic fracture toughness as a function of loading rate for a silicon carbide (SiC-N).

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