A microscopic study on local strain rate sensitivity of polypropylene syntactic foam with microballoons

The local strain rate sensitivity of polypropylene syntactic foams with polymer microballoons in the relative density from 0.5 to 0.8 is studied at the nominal strain rate ranged from 10^-1 to 10² s ^-1. Johnson-Cook law is employed to show the viscoelastic properties of polymer syntactic foams. A microscopic investigation reveals that the strain rate sensitivity and the effect of localised deformations can be observed at the higher strain rate (50-100 s^-1). The local deformation mechanism is different in different strain rate regimes due to the effect of local strain rate. At strain rates below 10 s^-1, cell-face stretching is the dominant deformation mechanism. At strain rates from 50 s^-1 to 100 s^-1, cell-face stretching and cell-edge bending are the main deformation mechanism.