Viscoelasticity of Wood Composite Mats During Consolidation

Chunping Dai

Abstract


To improve our understanding of the wood composite hot-pressing process, viscoelastic consolidation of wood flake mats was investigated in terms of constituent flake properties and mat formation. A fundamental model of mat stress relaxation was developed based on the compressive stress relaxation of wood flakes and Poisson distribution of flake overlaps formed in the mat. Both stress relaxation and creep of wood flakes and flake mats at ambient condition were experimentally tested and analyzed. The results showed that the stress relaxation of wood flakes at different levels of compression follows linear double logarithmic relationships with varying slopes or rates of stress relaxation. The mat stress relaxation model was validated by comparing the model predictions with the experimental data. Like stress relaxation, creep of flakes also varies with the level of compression. Due to porosity difference, creep of flake mats is not quantitatively comparable to creep of flakes in terms of relative creep strain. Instead, relative creep compaction ratio of mats is comparable to that of wood flakes.

Keywords


Wood composites;modeling;mat consolidation;viscoelasticity;pressing

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