caa a22 4500 469123605 CHVBK 20180323133145.0 cr unu---uuuuu 170328e19920801xx s 000 0 eng 10.1007/BF00015865 doi (NATIONALLICENCE)springer-10.1007/BF00015865 Theocaris Pericles National Academy of Athens, P.O. Box 77230, 175-10, Athens, Greece aut Failure modes of closed-cell polyurethane foams [Elektronische Daten] [Pericles Theocaris] The failure modes of closed-cell polyurethane foams were studied by applying the elliptic paraboloid failure surface criterion. A series of three polyurethane rigid foams (PUR-foams) were examined presenting different amounts of porosity from a highly porous material having a low density of 64 kg/m3 to a compact one with a density of 192 kg/m3. All these PUR-foams were of the same batch of material presenting a cell-wall density ϱ5=1200 kg/m3. Samples were tested in simple tension and compression along the three principal axes of anisotropy of the materials. It was shown that all three types of foams may be closely represented by transversely isotropic materials. The elliptic paraboloid failure surfaces (EPFS) for these three materials were defined from the six values of principal failure stresses in tension and compression. It was shown that the theoretically plotted paraboloid surfaces along all their principal-plane intersections were in good agreement with experiments. Since cellular materials collapse, either under elastic buckling in the compressive octant of the principal stress space, or under fast brittle fracture in the tensile octant, it was shown that the elliptic paraboloid failure surface is truncated by the intersection of the EPFS and an ellipsoid whose position and dimensions are interrelated with those of the EPFS. Again, experimental evidence with elastic buckling of foams corroborated the results of this theory. An important feature for the failure behavior of the foams was derived by this study according to which the foamed materials change mode of failure from a compression strong to a tension strong mode as their porosity is increased. In between they pass through a quasi-isotropic state. Kluwer Academic Publishers, 1992 International Journal of Fracture Kluwer Academic Publishers 56/4(1992-08-01), 353-375 0376-9429 56:4<353 1992 56 10704 https://doi.org/10.1007/BF00015865 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00015865 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Theocaris Pericles National Academy of Athens, P.O. Box 77230, 175-10, Athens, Greece aut NATIONALLICENCE 773 0- International Journal of Fracture Kluwer Academic Publishers 56/4(1992-08-01), 353-375 0376-9429 56:4<353 1992 56 10704 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer