Application of Fractional Derivatives Models to Time-dependent Materials

Visco-elastic properties of polymers and elastomers are of fundamental importance to understand their mechanical behavior, especially dealing with dynamic and vibration problems. In this paper experimental results of a series of compression and tension tests on specimens of styrene-butadiene rubber and polypropylene plastic are presented; tests consist in cyclic loading at different frequencies, relaxation tests and creep tests. Experimental data are used to calibrate some linear viscoelastic models; besides the classical approach based on a combination in series or parallel of standard mechanical elements (springs and dashpots), a new method based on differential equations of fractional order (Fractional Derivative Model) is investigated. The two approaches are compared analyzing their capability to reproduce the experimental data.