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Inhomogeneity in a sheared elastomeric layer as a result of thermally induced scission and healing. (English) Zbl 1167.74362

Summary: When an elastomeric material is held at a fixed stretch at a sufficiently high temperature, the macromolecular network junctions undergo time-dependent scission and the applied force relaxes with time. The affected molecules recoil and re-crosslink to form a new network that is stress free in a new reference configuration. Experiments indicate that this process only occurs when the temperature exceeds a critical value, that it occurs faster at higher temperatures and stops when temperature is reduced below the critical value. They also indicate that if the material is loaded during the scission and re-crosslinking process and is then unloaded and cooled, it has a permanent set and a modified stiffness.
This work considers the consequences of these events on an elastomeric component. An elastomeric layer is sheared with one surface held at a constant temperature while the other surface is heated and then cooled. Using a constitutive equation that accounts for the scission and re-crosslinking process, it is shown that the layer develops an inhomogeneous shear modulus as well as permanent set. An expression is developed for the shear modulus at a material element in terms of its temperature history and scission and re-cosslinking kinetics. A numerical example illustrates the nature of the inhomogeneity.

MSC:

74E05 Inhomogeneity in solid mechanics
74F05 Thermal effects in solid mechanics
74B20 Nonlinear elasticity
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