Research of expanded polystyrene (EPS) stress relaxation under uniaxial loading conditions using statistical design method of experiments

The results of stress relaxation under uniaxial compression experimental research of expanded polystyrene products with the types of EPS 80/90/100/120 and EPS 150 at a constant ε₀=(1,2±0,2)%, that was fixed at a specific compressive load σ_н(=0,35·σ_10%) acting perpendicular to the surface of products, are presented. The method of mathematical and statistical experimental design optimization models taking into account the thickness of specimens is proposed to determine the relaxation coefficient K_r at the time t=8 h, the attenuation factor to reduce the compressive stress K_atten and relaxation compliance J_r(t→∞). The graphical interpretation of the models is presented: depending level line of the relaxation coefficient K_r at the time t=8 h, relaxation resistance coefficient K_r and compliance with the relaxation J_r to t→∞. On the basis of quantitative experimental values of compliance J_r (t→∞) with the relaxation in the range of permanent compressive strain ε₀=(1,2±0,2)%, the linear equations of interdependence between J_r (t→∞) and J_c(t_n=122 days) are given. Empirical equations for the calculation of the established equilibrium stress at a relaxation are offered.

S.I VAITKUS, Candidate of Sciences (Engineering) (This email address is being protected from spambots. You need JavaScript enabled to view it.)
I.J. GNIP, Candidate of Sciences (Engineering)

Vilnius Gediminas Technical University (Scientific Institute «Insulation») (28, Linkmyanu Street, Vilnius, 08217, Lithuania)

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