By Janis Stoffel
Liquid Armour
One application of non-Newtonian fluid could be a flexible military suit. Inside the suit there would be some kind of non-Newtonian fluid which would remain in liquid state while the soldier stands still, moves or runs, but would immediately go into the solid state when the bullet hits, acting as a sort of flexible bulletproof armor.
The main problems in designing such a protective armor is to make detailed calculations of:
Viscous coupling In four-wheel drive vehicles the driving and non-driving shafts are connected by a mechanical device called viscous coupling. The device consists of many circular plates with perforations. Those plates are placed in a drum and fitted very close to each other. Inside the drum there is a non-Newtonian fluid whose viscosity increases with shear stress. Plates are alternately connected to the driving shaft at one end and non-driving shaft at the other.
When a vehicle moves without skidding, both shafts together with their connected plates rotate with the same rotational speed. The non-Newtonian fluid remains in liquid state due to the absence of shear between adjacent plates. But, in a situation in which the vehicle is skidding the difference in rotational speed of adjacent plates produces shear stress: the fluid abruptly increases its viscosity (it responds much like a solid) and therefore transfers motion between plates. The end effect is a transfer of torque from driving to the non-driving shaft - in other words, we switch from a two-wheel to a four-wheel drive.
Body armour
Various corporate and government entities are researching the application of shear thickening fluids for use as body armor. Such a system could allow the wearer flexibility for a normal range of movement, yet provide rigidity to resist piercing by bullets, stabbing knife blows, and similar attacks. The principle is similar to that of mail armor, though body armor using a dilatant would be much lighter. The dilatant fluid would disperse the force of a sudden blow over a wider area of the user's body, reducing the blunt force trauma. However, against slow attacks which would allow flow to occur, such as a slow but forceful stab, the dilatant would not provide any additional protection.
In one study, standard Kevlar fabric was compared to a composite armor of Kevlar and a proprietary shear-thickening fluid. The results showed that the Kevlar/fluid combination performed better than the pure-Kevlar material, despite having less than one-third the Kevlar thickness.
Two examples of dilatant materials being used in personal protective equipment are d3o, and 'Active Protection System', manufactured by Dow Corning.
Non-Newtonian fluids are also used in modern iPhone cases, the impact shield.
One application of non-Newtonian fluid could be a flexible military suit. Inside the suit there would be some kind of non-Newtonian fluid which would remain in liquid state while the soldier stands still, moves or runs, but would immediately go into the solid state when the bullet hits, acting as a sort of flexible bulletproof armor.
The main problems in designing such a protective armor is to make detailed calculations of:
- stresses which occurs during different soldier's activities and during hits of a bullet
- viscosity vs. stress dependence of the fluid
- mechanical properties of the fluid while in liquid and solid state
- and, of course, design and synthesize a fluid with the desired properties calculated above
Viscous coupling In four-wheel drive vehicles the driving and non-driving shafts are connected by a mechanical device called viscous coupling. The device consists of many circular plates with perforations. Those plates are placed in a drum and fitted very close to each other. Inside the drum there is a non-Newtonian fluid whose viscosity increases with shear stress. Plates are alternately connected to the driving shaft at one end and non-driving shaft at the other.
When a vehicle moves without skidding, both shafts together with their connected plates rotate with the same rotational speed. The non-Newtonian fluid remains in liquid state due to the absence of shear between adjacent plates. But, in a situation in which the vehicle is skidding the difference in rotational speed of adjacent plates produces shear stress: the fluid abruptly increases its viscosity (it responds much like a solid) and therefore transfers motion between plates. The end effect is a transfer of torque from driving to the non-driving shaft - in other words, we switch from a two-wheel to a four-wheel drive.
Body armour
Various corporate and government entities are researching the application of shear thickening fluids for use as body armor. Such a system could allow the wearer flexibility for a normal range of movement, yet provide rigidity to resist piercing by bullets, stabbing knife blows, and similar attacks. The principle is similar to that of mail armor, though body armor using a dilatant would be much lighter. The dilatant fluid would disperse the force of a sudden blow over a wider area of the user's body, reducing the blunt force trauma. However, against slow attacks which would allow flow to occur, such as a slow but forceful stab, the dilatant would not provide any additional protection.
In one study, standard Kevlar fabric was compared to a composite armor of Kevlar and a proprietary shear-thickening fluid. The results showed that the Kevlar/fluid combination performed better than the pure-Kevlar material, despite having less than one-third the Kevlar thickness.
Two examples of dilatant materials being used in personal protective equipment are d3o, and 'Active Protection System', manufactured by Dow Corning.
Non-Newtonian fluids are also used in modern iPhone cases, the impact shield.