It is noted from Fig. 5(a) and (b) that the net section stress drops to zero in the tensile tests at an opening displacement Du=1–2 mm for both foams. The displacement at fracture is almost independent of a/W for the Alcan foam, see Fig. 5(b); for Alporas foam, it decreases by about a factor of 2 when a/W is increased from 0 to 0.6, refer to Fig. 5(a). In contrast, the compressive net section stress remains almost constant with increasing deformation; the tests were terminated before the notch faces came into contact. A similar response has been observed previously [13] in deep notch compression tests on the Alporas foam.