Viscoelastic properties cords

This study Is concerned exclusively with the role and optimization of viscoelastic properties of cords, an area where tire mechanics made very significant progress during the recent few years. 

When the strain amplitude Is relatively large as In the case of tire cord In a running tire, the viscoelastic behavior Is no longer linear. The stress-strain loop Is not elliptic but distorted (Figure 1). The material properties In the nonlinear regime can not be represented with the real and Imaginary moduli. In the present study, we characterize the viscoelastic properties In nonlinear regime by the effective dynamic modulus and mechanical loss.(J )... 

Figure 9. Effect of twist on viscoelastic properties of PET cords. Reproduced with permission from Ref. 2. Copyright 1979 ASIH,...

Andrescai A, Cordes HG, Herwig H et al (1976) Influence of long-chain branching on the viscoelastic properties of low-density polyethyltaies. Angew Chem bit Ed 15 630-632... 

Hyaluronic acid is found in most connective tissues including human vitreous, skin, synovial fluid and umbilical cord. One of its biological roles is its ability to contain large amounts of water in intercellular space. It can thus locate cells in a jelly-like matrix and resistance of tissue towards infection may partly depend on this property. The intercellular matrix has a viscoelastic nature [75-77] and is thought to have a role in absorbing shock. Hyaluronic acid can exist in the form of aggregates [81,82] or a network structure [78-80], Such a network offers a filter or macromolecular sieve-like resistance to other molecules as well as cells [83,84],... 

A major difference may exist between HA in vivo and HA chains that are extricated from the in situ situation. Very little is known about the properties of the HA within the narrow confines of the ECM or the restricted volume of the intercellular space. However, when HA undergoes aqueous extraction from major sources, such as from the mucoid layer of the rooster comb, from joint fluid, the perivascular space of the umbilical cord (Wharton s jelly), or from bacterial capsules, the extraction fluid has very high viscoelasticity. Such HA is in a random coil conformation. However, HA is unlikely to be in such a conformation in vivo, and little is known about the state of the HA within tight tissue spaces. It is probably much more structured, and probably has many additional functions that are unknown and lost when examined in vitro [15]. 

When a viscoelastic material such as tire cord or rubber Is subjected to a small amplitude sinusoidal straining, the resulting stress-strain curve Is an ellipse and the material properties are characterized by the real and Imaginary moduli E and E" or the ratio E /E ( tan[Pg.372]

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