Experimental Methods for Hard Viscoelastic Solids

The devices of the preceding chapter are designed for viscoelastic solids with moduli in the general range from 10 to 10 dynes/cm (10 to 10 Pa) some are appropriate for low values of tan 6, others for intermediate to high tan 8. For harder solids with moduli in the range of 10 to 10 dynes/cm (10 to 10 Pa), there is no difference in principle in the application of the same experimental methods, and indeed some of them can be used without modification, but some new features appear with the increase in stiffness of several orders of magnitude. 

Geometries, coordinates, and dimensions for investigation of hard viscoelastic solids (in addition to some shown in Figs. 5-1 and 6-1). (a) cantilever with rectangular cross-section (b) cantilever with circular cross-section (c) flexure of rectangular bar with both ends clamped (d) flexure of rectangular bar with knife edge support. 

X2 = linear displacement (perpendicular to direction of stretch in sample) 

A modification of arrangement (d) in which the load is applied by two knife edge contacts has also been used.  

An extremely versatile and accurate instrument designed by Sternstein has been used to subject hard polymeric solids to combined tension and torsion and can be programmed for computerized data acquisition and processing with a variety of loading patterns including creep, relaxation, and recovery. 

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