Methods for Measuring Dynamic Mechanical Properties of Rubber-Like Materials

Five methods are described for measuring the complex differential dynamic Young's modulus of rubber-like materials, under conditions of very small sinusoidal strain variations, at frequencies from 10−1 to 105 cycles per second and in a temperature range which at its widest limits extends from minus 60 to plus 100 degrees centigrade. These methods are (1) measurement of the frequency of oscillation and the decrement of a ``rocking-beam oscillator'' in which the restoring force is supplied by rubber (0.1 to 25 c.p.s.); (2) measurement of the frequency of resonance and the band width of a rubber reed which executes forced oscillation (10 to 500 c.p.s.); (3) measurement of the phase velocity and the attenuation of longitudinal waves in a thin rubber strip in the absence of standing waves (1 to 40 Kc); (4) measurement of the frequency of longitudinal-wave resonance and the band-width of a half-wave transmission line (below 300 c.p.s.); (5) measurement of the change in the frequency of resonance and the change in the band width of a magnetostrictive rod against whose end a rubber sample is pressed (12 to 120 Kc). Equations are developed for calculating the complex modulus from the results of each experiment, and the practical advantages and limitations of the methods are described.