Thermo-hyrgo-mechanical processes for the densification and forming of wood: Continuum-mechanical material formulation and structural simulations

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Wood has been used as solid wood for the construction of building structures since centuries. Recently, increased ecological as well as technical requirements lead to a demand for improved properties of building materials. The Institut of Steel and Timber Construction of TU Dresden (ISH) develops the technology of wood forming based on the thermo-hygro-mechanical properties of the raw material wood.The numerical simulation of the wood forming process and the behavior of structural components made from formed wood using the finite element method require a realistic constitutive model in order to describe the thermo-hygro-mechanical material behavior of wood at finite deformations.Main aim of the renewal proposal at hand is the preparation of numerical tools and methods for the simulation and design of optimal industrial products made from formed wood. The numerical simulation provides the means to achieve a deep insight into the multi-physical effects and phenomena within the structures during application of the forming technology.The basis for modelling wood densification as well as wood forming is achieved during the first funding period. In order to further develop and to validate the thermo-hygroscopic anisotropic material modelling of wood at large deformations, a comparison of simulation results with experimental data provided by ISH is carried out.Further developments are made by modelling the current density of wood under consideration of its raw material and its bound water. To this purpose, a modification of the mass balance mass of moisture and of displacement dependent continuum mechanical processes are carried out with respect to the simulation of the manufacturing of formed wood.Furthermore, a thermo-hygroscopic finite surface element is formulated as well as related constitutive laws, in order to model the moisture in- and out flow and thermal convective phenomena.Additionally, parameter studies are carried out with respect to the identification of significantly influencing values, since only few qualitative and empirical preliminary work regarding this technology is existing.Finally, realistic and industry-related numerical simulations of structural components made from formed wood are carried out and analyzed, in order to demonstrate the practical applicability of the forming technology and its numerical modelling.