Abstract: The replacement of synthetic foam materials using natural biological ones is of great significance for saving energy/resources and reducing environmental pollutions. Here we characterized the microstructure and mechanical properties of natural cornstalk pith, which has a large annual output yet lacks an effective exploitation, and evaluated its feasibility for applications as a substitute for synthetic foam materials. The cornstalk pith was revealed to be a cellular material composed of closed cells elongated along the growth direction of corn plant and reinforced by well-aligned vascular bundles penetrating the foam matrix. The compressive behavior is featured by a stable stress plateau which is favorable for energy absorption with its mechanical properties largely dependent on the hydration state and loading configuration. In particular, the initial dimension and mechanical properties of cornstalk pith can be effectively recovered after deformation simply by hydration treatment owing to swelling effect caused by the turgor pressure from osmosis. The cornstalk pith demonstrates an outstanding combination of low density and high energy absorption efficiency among various foam materials, specifically with its plateau stress and energy absorption comparable or even superior to those of some typical synthetic foam materials. These along with the huge resources and good biodegradability make it a promising natural energy absorbing cellular material for replacing synthetic counterparts.

Key words: cornstalk pith, energy absorption, foam, hydration, self-recovery