A project to develop pedestrian friendly motor vehicle front ends using a Shock Absorbing Liquid (SALi) developed by UK engineer Bill Courtney has recently received £256,000 of British government funding, with the American industrial giant Dow agreeing to invest a further £364,000 in the project.
SALi is a patented elastic shock absorbing fluid for protecting the human body and other delicate objects. When suitably packaged, the fluid combines the elastic properties of an elastomeric foam with the viscous damping and pressure equalisation properties of liquids.
The essential ingredients of any SALi based impact absorber are a number of small, closely packed resilient capsules with an incompressible matrix fluid filling all of the void space between them, with the mixture stored in a container or strong, flexible package, which does not stretch significantly during an impact.
During an impact, the capsules are compressed and occupy a smaller fraction of the total volume of the capsules plus matrix fluid mixture. This means that, even if the capsules are close packed when in the rest state, they become separated by layers of matrix fluid during the impact, enabling them to move freely inside the package, to accommodate the shape of the front face of the impacting body.
The matrix fluid also permits hydraulic pressure transmission, allowing elastomeric capsules to the sides of the impact zone to participate in the energy absorbing process. The capsules immersed in the matrix fluid create an inhomogeneous mixture, which is predicted to scatter shock and other acoustic waves, accounting for its blast mitigation properties.
SALi can also be incorporated into helmets, gloves, shin pads, saddles, hip pads for Osteoporosis sufferers, car bumpers, suspension systems, fuel-tanks of aircraft and prefabricated structures in war zones.
It’s developers say that it exhibits superior impact energy reduction benefits, compared with existing shock absorbing materials. Preliminary experiments also indicate that it has good blast mitigation properties.
SALi is re-usable, allowing it to accept many impacts. It is also good for the environment, because it can be recycled locally, without using expensive heat treatments.