Figure 8.

Mechanical compression tests of CNF foams produced by the stirred freezing process and a CNF concentration equal to 0.69 wt%. (a) Compression stress as function of compression strain including 9 cycles at increasing maximum compression strain up to 50%. The number beside each curve denote the cycle number. (b) Residual strain as function of the maximum compression strain as extracted from the data in (a). The limit for the elastic behavior, corresponding to zero residual stress, is found for a maximum compression strain of ~8%. The fitting line is a polynomial curve, while the dashed gray line is the quadrant bisector.