Impact of a pressurized membrane: Coefficient of restitution

Pressurized membranes are usually used for low cost structures (e.g., inflatable beds), impact protections (e.g., airbags), or sport balls. The last two examples deal with impacts on the human body. Underinflated protective membranes are not effective whereas overinflated objects can cause injury at impact. The coefficient of restitution represents the ability of a membrane to dissipate energy during an impact. Its dependence on membrane properties and inflation pressure is investigated on a model experiment using a spherical membrane. The coefficient of restitution increases with inflation pressure but decreases with impact speed. For a spherical membrane, it is shown that kinetic energy is lost by transfer to vibration modes. A physical modeling of a spherical membrane impact is built considering a quasistatic impact with small indentation. Finally, the dependency of the coefficient of restitution with mechanical parameters, pressurization, and impact characteristics is given.