Petal formation law in a cellophane diaphragm subjected to a pressure difference

In this study, a layer of cellophane, subjected to an air-pressure difference, was ruptured using a piercing needle. Accordingly, petal-like fragmentation was observed in the layer via high-speed imaging. Two types of crack-propagation regimes were subsequently observed experimentally. If a tensile stress lower than 20.6 MPa acted on the cellophane diaphragm, a single crack was generated, whose propagation speed was lower than that under higher-stress conditions. For tensile stresses greater than 23.7 MPa, the crack-propagation speed remained constant at approximately 0.86 km/s, even after altering the device size, pressure, and humidity on the low-pressure side. The number of cracks equidistant from the piercing point was expressed as a linear function of the tensile stress acting on the diaphragm.