Size effect on stress–strain relation of neat polyurethane foam

The basic mechanical properties of a structural engineering material are usually obtained by uniaxial tension testing using a dog-bone type specimen and little attention is paid to the size of the specimen or the size of the strain measuring gage. We show that for the neat polyurethane foam material, two different size specimens exhibit a large difference on their mechanical response to load. A unique experimental mechanics technique called the multi-scale speckle method is introduced to obtain the mechanical properties of the specimens. The larger specimens were tested using a tabletop testing machine, while the smaller ones were tested inside the chamber of a scanning electron microscope.