FEM simulation of the hygro-thermal behaviour of wood under surface densification at high temperature

Surface densification of solid wood increases the density on the surface, when compressed by single side heated press. A recent experimental study has pointed out the influence of the process parameters on the development of the density profiles in the modified samples. Numerical modelling can help to optimize the experimental work which is often time consuming and laborious due to the large amount of experiments required to check the influence of the pressing parameters. In the present work, a FEM simulation of the hygro-thermal behaviour of wood under surface densification is proposed by using a three-dimensional hygro-thermal model based on earlier literature approaches. The model is implemented in a user subroutine of the FEM code Abaqus starting from the definition of a weak form of the governing hygro-thermal equations of the problem. The numerical profiles of moisture content and temperature during the wood densification process are simulated for some wood specimens tested in a previous study. Conclusions are given on the relationship between these profiles and the experimental density profiles due to different process parameters.