Shear-thickening

Definition

Shear-thickening refers to a behavior exhibited by some non-Newtonian fluids where their viscosity increases with an increase in shear rate. In simple terms, as you stir or apply force to these fluids, they become thicker and more resistant to flow, making them behave more like a solid. This phenomenon is crucial in understanding how certain materials, like cornstarch mixed with water or certain polymer solutions, respond under different conditions.

5 Must Know Facts For Your Next Test

1. Shear-thickening behavior is often observed in materials like cornstarch-water mixtures, which become solid-like when subjected to sudden stress.
2. This phenomenon can be explained by the interactions between particles in a suspension, which can form temporary structures that resist flow under stress.
3. Shear-thickening is distinct from shear-thinning, where a fluid becomes less viscous with increased shear rate.
4. Applications of shear-thickening materials include protective gear, such as body armor, which remains flexible under normal conditions but hardens upon impact.
5. Understanding shear-thickening is important in industries like food processing and cosmetics, where the texture and flow of products are critical.

Review Questions

• How does shear-thickening differ from shear-thinning in terms of fluid behavior under stress?
  • Shear-thickening and shear-thinning are two opposing behaviors of non-Newtonian fluids when stress is applied. Shear-thickening fluids increase in viscosity with higher shear rates, becoming more solid-like, whereas shear-thinning fluids decrease in viscosity and become more fluid-like under the same conditions. This distinction is important for applications where material response to forces is critical, such as in protective equipment or food products.
• Discuss the role of particle interactions in the mechanism of shear-thickening behavior.
  • Particle interactions play a significant role in shear-thickening behavior by forming transient structures within the fluid. When stress is applied, particles may aggregate and create a network that impedes flow, leading to an increase in viscosity. This phenomenon can be observed in mixtures like cornstarch and water, where the particles' arrangement changes under stress, resulting in a thicker consistency that resists deformation.
• Evaluate the practical applications of shear-thickening materials and their importance in various industries.
  • Shear-thickening materials have valuable applications across several industries due to their unique properties. For example, they are used in body armor that remains flexible during regular movement but becomes rigid upon impact, offering protection. In food processing and cosmetics, understanding how these materials behave under stress is essential for controlling product texture and stability. The versatility of shear-thickening materials highlights their significance in innovation and safety across multiple fields.

Related terms

Viscosity: A measure of a fluid's resistance to deformation or flow, which can change under different conditions like temperature and shear rate.

Non-Newtonian Fluid: Fluids whose flow behavior cannot be described by a single constant viscosity, showing varied viscosity depending on the applied shear rate.

Shear Rate: The rate at which a fluid is deformed or the velocity gradient of the fluid layers as they slide past one another.