Shear stresses, tearing under

Such effects are likely to be important. The use of SP interactions to create bioinspired material properties (e.g., see Chap. 9) implies that the ultimate yield behavior of SP materials could depend on the mechanical response of supramolecular interactions. Paulusse and Sijbesma (2004) have also shown that ultrasound-generated shear stresses can mechanically tear apart coordination SPs, damage that is subsequently repaired during dynamic equilibration once the shear stresses are removed. The mechanical response of supramolecular interactions within materials has potentially important consequences in the context of self-repairing materials, where the mpture of sacrificial supramolecular interactions protects a permanent, underlying materials architecture. The dynamic repair of the SP component in... 

Tearing under shear stresses (schematic). (From Knauss (1970) and Ahagon et al. 

Although the fluids most often considered in biofluid mechanics studies are blood and air, other fluids such as urine, perspiration, tears, ocular aqueous and vitreous fluids, and the synovial fluid in the joints can also be important in evaluating tissue system behavioral responses to induced chemical and physical stresses. For purposes of analysis, these fluids are often assumed to exhibit Newtonian behavior, although the synovial fluid and blood under certain conditions can be non-Newtonian. Since blood is a suspension it has interesting properties it behaves as a Newtonian fluid for large shear rates, but is highly non-Newtonian for low shear rates. The synovial fluid exhibits viscoelastic characteristics that are particularly suited to its function of j oint lubrication, for which elasticity is beneficial. These viscoelastic characteristics must be accounted for when considering tissue therapy for joint injuries. 

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