FATIGUE STRENGTH OF FOAMED POLYMERS

Abstract

Statement of the problem. The durability of structures largely depends on the ability of heat-insulating products, including those based on foamed plastics, to withstand the action of alternating loads for a long time. Creep deformations can be formed in foam plastics as a result of prolonged vibrations, which leads to violation of the integrity of the insulating shell and affects the reliability of enclosing structures. The development and implementation of a methodology for assessing the fatigue strength of foamed polymers is an urgent task. The aim of the study is to test the developed methodology and experimentally determine the change in vibrational creep deformations of rigid foam plastics over time. Results. It has been established that the influence of temperature fluctuations in combination with mechanical influences leads to cyclic stresses in the insulating layer and also affects the strength and elastic modulus of the polymer matrix. An assessment of the nature of the influence of temperature on the fatigue strength of rigid foam plastics showed that the limits of the fatigue strength of materials have extrema at a temperature of 20 °C. Decreasing the temperature to minus 40 °C or its gradual increase to 80 °C leads to a decrease in fatigue strength. The most significant reduction occurs in polyurethane foams and carbamide foams. Conclusions. Rigid gas-filled plastics have a number of promising properties, such as strength and reduced flammability. The results obtained are in full agreement with modern ideas about the mechanism of structural relationships of the structure and their influence on the properties of foamed polymers. The practical significance of the research lies both in obtaining data on the resistance of rigid foams and in the possibility of using the developed methodology for other foams.