Strains in an Inflated Rubber Sheet, and the Mechanism of Bursting

Abstract The two principal strains in a circular sheet of rubber clamped round its circumference and inflated are measured at all points on the surface of the spheroidal balloon thus formed. The principal strains may show relatively-large variations over an area in which the form is nearly spherical and the thickness is approximately constant. The reasons for this, and for certain other effects brought out in the experiments, are discussed. In experiments on the bursting of sheets of various rubbers (natural and synthetic), there appeared to be a general relation between the hardness at the instant of breaking and the number and regularity of the radial tears. From the strain measurements it is concluded that these radial tears are not caused by the relatively slight radial orientation of the molecules in the sheet. A detailed mechanism of bursting is suggested, in which the radial tears are compared with the radial cracks associated with glass fractures.