Influence of geometry and density on the compressive behavior of cellulose based foam

Abstract

Foam materials have become integral in various industries in recent decades due to their lightweight nature and unique mechanical properties. Despite their versatility, challenges persist especially in their shift from being a fossil-fuel-based to bio-based material, particularly in mechanical behavior such as shape recovery capacity. This thesis aims to advance the understanding and optimization of compression properties of bio-based foam materials developed by Woamy Oy, crucial for sustainability and broader application potential. The experimental approach taken in this study revolves around exploiting various foam orientation, density, shapes, and Origami patterns in a compression loading scenario with the goal of identifying the most promising configuration for future development and to provide a more quantitative understanding of the material.

It is established that increasing the density by introducing permanent compressive damage to foam sheets in a zero-degree orientation stacking scenario could result in higher specific compressive stress at various strain values with a 42.2 percent increase at peak values as a results of efforts in this work. In addition, optical microscopy technique is used to investigate the effect of pre-compression on the microstructure of the material before and after compressing the samples to 70 percent of their original height. The results show that the microstructure of the samples with higher density are packed with microfibers more than it is in the ones with lower density. Deformation is also observed in the cells of the samples with higher density as a result of pre-compression. Cells and voids in the microstructure of the material show recovery of shape even after testing, with more recovery in the samples with lower density.