The Variety of the Stress-strain Response of Silicone Foam after Aging.

The mechanical properties of silicone foam will degrade when exposed to environmental loads such as temperature and pressure for a long time. In recent years, the variation law of the stress-strain response of silicone foam during the aging process has received more and more attention, but there are few works that quantitatively analyze the variation of the stress-strain response. In this work, we quantitatively analyzed the variation law of the stress-strain response of silicone foam during aging by the constitutive model. Firstly, the accelerated aging test of silicone rubber foam under long-term compressive strain was carried out, and its compression set, stress relaxation and strain stress curves of different aging degrees were obtained. Further, degenerate trajectory equations for the compression set and stress-relaxation were obtained. In addition, the hyper-foam constitutive model was obtained by fitting stress-strain curves, and the changes in the model parameters after aging were studied. The results show that the compressed set and stress-relaxation are exponential functions of time, while different to existing research findings, we found that the stress-strain curves do not change monotonically with increasing time, which first softens, then hardens, and finally softens. Additionally, to better understand the changing trend of the stress-strain response, the correlation between the stress-strain curve and the compression set and stress-relaxation was discussed qualitatively. Finally, in the stage of monotonic change of the stress-strain curve, the exponential function of the model parameters with the increase of aging time was obtained.