Textile reinforcement of multidimensional formable wood

Abstract

The thermo-mechanical densification of wood leads to new material characteristics with a plasticity of more than 50 %. The compression process can be influenced by different material and process parameters. By subsequent thermo-hydro-mechanical forming, production of three-dimensional structures is viable. Additional textile reinforcement can increase the formability of partly densified wood structures transverse to the fibre direction. At the same time, the strain will be limited in order to avert premature local failure in the densified wood cell structure. Forming tests confirm the significant increase in drapability by jute and glass fibre reinforcement. Swelling pressure tests were carried out on three densified wood species to determine the internal stresses of the glue line. Thereby, lower compression stresses in poplar (Populus nigra L.) than in lime (Tilia cordata Mill.) or pine (Pinus silvestris L.) were measured. Compression stresses correlate with the density and will increase at higher densification. Furthermore, the determination of local deformation caused by densification and moulding was to be evaluated. The tests were performed by measurement of recovery during water storage using grid strain analysis. Specimens with lower process temperature (75 °C) and high degree of densification (50 %) were less homogenously deformed than samples at high temperatures (125 °C). In summary, moulding optimised, biaxially densified end grain boards with textile reinforcement (jute) should be preferably used for technical applications such as interior fitting or the use in automotive engineering.