Exact computation of creep compliance and relaxation modulus from complex modulus measurement data

It is well-known that for a linear viscoelastic material, there is a relationship between the complex modulus, the creep function and the relaxation modulus. It should be sufficient to collect one of these functions by a measurement to obtain the two other functions. However, this process seems to be rarely used. One reason for this may be the very large frequency intervals over which the Fourier transform should be computed. It is not unusual to find a ratio of 1030 between the lowest and the highest frequencies. We propose a semi-analytical algorithm for computing the creep and the relaxation functions from complex modulus data. Exact in nature, it makes use of very basic assumptions. Good correlation with approximate alternative methods is found. In this paper, we illustrate our method using some examples of creep compliance and relaxation modulus synthesis from the master curves.