Viscoelastic characterization of seven laminated glass interlayer materials from static tests

•Stress relaxation tests were conducted on seven laminated glass interlayers.•The master curves were obtained by using the t-T-P shifting (CFS) algorithm.•The stiffness of all tested interlayers decreased over time and temperature.•An equation to fit each relaxation master curve was represented by a Prony series.•The storage and loss modulus were obtained by using interconversion methods. The mechanical behaviour of laminated glass is strongly affected by the polymeric interlayer placed between glass layers. In general, this interlayer is a viscoelastic material, and therefore it may experience creep and stress relaxation when subjected for an extended period to a constant stress or strain respectively. In this study, seven different commercial interlayer materials (EVALAM, EVASAFE, PVB BG-R20, Saflex DG-41, PVB ES, SentryGlas, and TPU) were evaluated with relaxation tests at different temperatures, in order to build the relaxation master curves through the time-temperature superposition principle. A generalized Maxwell model was chosen to describe the viscoelastic behaviour of the tested materials. This paper includes the coefficients of the Prony series that fit better the experimental results. This paper has two main goals. First, to present the Prony coefficients (ei and τi), which can then be used to create numerical models that take into consideration the time and temperature-dependant behaviour of the interlayer. Second, to provide the two components of the complex modulus (E*(ω)) of each material, the storage modulus (E’(ω)) and the loss modulus (E’’(ω)), which can be obtained from the relaxation modulus (E(t)) by using analytical interconversions.