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SALi - What Is SALi Technology(TM)?
SALi Technology provides a new way of protecting people and property from impacts, vibrations and shock waves. A brief introduction to SALi Basic SALi based impact absorbers consist of lots of small, elastic capsules blended with a liquid, mastic or grease, with the mixture being retained in a strong package, which does not stretch significantly during an impact.
SALi impact absorbers = lots of elastic capsules + matrix fluid How does it work?
Figure 1. During an impact the capsules shrink in size as they are compressed on all sides by the matrix fluid. The capsules, lubricated by the fluid, re-arrange themselves inside the package, so that the front face of the package takes up the shape of the impacting body. In principle any liquid or grease which allows the hydraulic transfer of pressure can be used as the matrix fluid. In experiments liquid paraffin, glycol anti-freeze, wall-paper paste, Vaseline, mastic sealant and a range of engineering greases have been used as the matrix fluid. In order to maximise viscous damping very thick liquids having a viscosity similar to treacle are preferred. Non-setting gooey mastics are good because there are no leakage problems if the packaging is damaged. Shear thickening fluids are appealing because they allow the shape of the package to deform easily when bent slowly, but stiffen up during violent impacts. This feature is appealing in protective clothing, for example in pads to protect the spinal column of motorbike or equestrian riders. Elastomeric capsules investigated include expanded polystyrene beads, polymeric microspheres, bubbles cut from bubble packing and narrow diameter, open ended, hollow tubes, with filaments of air trapped inside them. All of the blends tested to date display useful impact absorbing characteristics. The diverse choice of materials available for making up blends of SALi should allow us to develop formulations to provide different elastic and viscous damping characteristics, to solve a wide range of impact absorbing problems. Keeping the weight down The basic SALi formulation as illustrated in Figure 1 has a single size range of capsules, with the matrix fluid occupying about 34% of the volume. The fluid fraction can be reduced to about 12% by using a blend of expanded polystyrene beads and polymeric microspheres. Blending is discussed in detail ob the Project advice page. (Se menu on the right.) Features & Benefits of SALi
The importance of SALi can judged from the support we have received:
SALi - SALi Vs. Foam Figure 2.
Packaging SALi
Strong, low
stretch clothing fabric forms a s suitable outer packing for many
applications, e.g. hip pads, sports equipment and basic research work
s
Figure 3 The left hand diagram shows correct, low stretch packaging being
used. The elastomeric capsules are compressed by the impact. Please note: "Shock Absorbing Liquid", "SALi" and "SALi Technology" are Cheshire Innovation trade marks. (TM) Their use to describe products or research results where low stretch packaging is not used will be considered as passing off, liable to deceive the public or funding bodies.
Find out more about SALi Technology projects
Limitations to our technology We specialise in impact, vibration and blast mitigating devices. Our markets, intellectual property and research data are restricted to dynamic applications, where the stresses on the SALi materials vary rapidly with time.
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