The rate dependence of confer polyurethane foams

A low resilience polyurethane foam was compressed under impact, constant st rain rate and creep loading conditions, over a range of temperatures. The f oam was characterised by scanning electron microscopy and image analysis. T he compressive collapse stress was found to be strongly strain rate and tem perature dependent, with the maximum rate effect in the impact velocity ran ge from 1 to 10 m/s. The highly viscoelastic response is due to the glass t ransition temperature being about 20 degrees C, and the low crystallinity o f the foam. The foam creep response is similar in many ways to that of conv entional flexible PU foam, but the creep strain can stabilise at intermedia te values.