Originally Posted by
Limper
The term "fluid" was mentioned a few times on the first page of the thread, in the context of the composition of certain helmets, and was a little confusing. Fluid describes both liquids and gasses. Fluids conform to the shape of the container they're in. Gasses are compressible fluids, liquids are incompressible fluids. Now go ahead and tell me I'm mansplaining.
Personally I intended "fluid" in the general sense that you mention (except for plasma of course) because I envision some shock absorption due to properties of the fluid flow, which could occur with either liquid or gas. That's really how a "gel helmet" might work, in addition to elastic cell walls. I'm not aware of the specifics of any product like that.
Someone was worried about air trapped in the cells (thinking that they don't store energy when compressed or something like that), but it doesn't have to do with the gel helmet question.