Modeling wood as a polymeric foam: an application to wood-based composite manufacture

The mechanical properties of cellular materials in compression are highly non-linear resulting from the collapse of the cellular structure. The amount and type of cellular collapse may be important in the resulting mechanical and physical properties of wood-based composites that are densified during hot-pressing. A strict analysis of the consolidation process during hot-pressing must examine the viscoelastic behavior of wood in transverse compression, which is highly stress non-linear. The work presented here examines the modeling of structural collapse using theories of cellular materials. The parameters studied include specimen geometry, moisture content, temperature, and orientation. The model uses wood density and cell modulus to predict macroscopic stress-strain relationships. Cell wall modulus is calculated from experimental results using the theories presented. The goal is to use this information as a form of non-linearizing function in a viscoelasticity analysis.