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L. Marsavina et alii, Frattura ed Integrità Strutturale, 34 (2015) 387-396; DOI: 10.3221/IGF-ESIS.34.43 394 experimental crack propagation angles differ from the predicted values. It can be also observed that the foam with density 300 kg/m 3 , with a microstructure close to a porous solid gives closer propagation angles to theoretical predictions (especially to MTS and ESIF), developed for brittle solid materials. Noury et al. [13] also found, investigating PVC foams in mixed mode loading, that MTS criterion gives the closest crack initiation angles to experimental values. Comparing the two type of specimens the crack initiation angles obtained on SEC specimens are above those results for testing ASCB specimens, and closer to the theoretical predictions. 0 15 30 45 60 75 90 0 15 30 45 60 75 90  c [degrees] Me [degrees] Density 100 kg/m 3 0 15 30 45 60 75 90 0 15 30 45 60 75 90  c [degrees] Me [degrees] Density 145 kg/m 3 a . Density 100 kg/m 3 b . Density 145 kg/m 3 0 15 30 45 60 75 90 0 15 30 45 60 75 90  c [degrees] Me [degrees] Density 300 kg/m 3 c . Density 300 kg/m 3 Legend Figure 7 : Comparison between experimental and theoretical crack initiation angles. In order to investigate the effect of density, the mean value of crack initiation angle is plotted versus the support position S 2 for ASCB specimens in Fig. 8.a, respectively versus loading angle  for SEC specimens, Fig. 8.b. The crack initiation angles are slightly different for the investigated densities. This is more pronounced for ASCB specimen, where maximum relative difference between densities 145 and 300 kg/m 3 and mode II loading ( S 2 =2.66 mm) is 22.3%. The maximum relative difference for SEC specimens was observed for loading angle   = 30 0 is 7.2% and this could be considered in the range of experimental determination. C ONCLUSIONS rack initiation angle on mixed mode loading for PUR foams of three different densities was investigated experimentally. Two specimens ASCB and SEC were considered, which allow to produce mixed mode loading only by changing some loading configurations. The obtained values were compared with four most used fracture C