Refinements on fracture toughness of PUR foams

Many efforts have been made in recent years to determine the fracture toughness of different types of foams in static and dynamic loading conditions. Taking into account that there is no standard method for the experimental determination of the fracture toughness of plastic foams different procedures and specimens were used. This paper presents the polyurethane foam fracture toughness results obtained for different foam densities. Two types of specimens were used for determining fracture toughness in modes I, II and a mixed one, and also the size effect, loading speed and loading direction were investigated. The paper proposed correlations for density, cell orientation and mixed mode loading based on the experimental testing results.