Experimental determination of critical stresses in sandwich cylinders under non-elastic conditions

In the present paper both the theoretical analysis of the compression process acting upon cylinders filled with the polyurethanes and the results of experiments have been presented. The experimental tests were performed under substantial plastic strains until the cylinder totally collapsed. Depending on the test bar slenderness ratio different strain patterns have been obtained. It is noteworthy that the critical compressive stresses curve obtained for the mean slenderness ratios neither coincides with the Tetmajer-Jasiński straight line nor with the Johnson-Ostenfeld parabola. A relatively simple function approximating the experimental results has been presented.