Analysis of drying stresses in green-glued plywood of Bete (Mansonia Altissima) specie

Abstract

The wood veneer dried artificially before gluing for the manufacture of plywood generally suffers several damages (cracks, deformations), decreasing the competitiveness of the process and limiting the use of nervous species of wood. The proposed solution is to glue them at the green state. However, during the drying process, superficial and internal cracks are observed. These cracks appear when stresses due to the anisotropic shrinkage of the plywood exceed the mechanical strength of the wood material. In the present study, the response of a 3-ply plywood of Bete (Mansonia altissima) glued at the green state is simulated in order to evaluate these stresses and deformations during drying using a finite element method program. The numerical results and associated experimental data make it possible to better analyze and understand the mechanical behavior of the plywood during drying in order to look for reliable plywood through new process.

Drying of green veneer hollow tubes monitored using stereo digital images correlation

“…Therefore, a suitable drying schedule or drying technique may help to limit cracking. For the fabrication of circular hollow tubes, however, vacuum drying with humidification cycle seems to have more potential (Makomra et al 2020). lowest RMSE variation.…”

“…Plasticisation due to high moisture content (MC) and high temperature for fabrication of green veneer also makes it possible to bend and form various shapes without damaging their integrity as it induces a plasticization process that softens the bond between hemicelluloses and lignin (Kollmann 1955;Bader and Nemeth 2019). Recent studies on Mansonia altissima and Pinus pinaster show that it is possible to manufacture plywood from green veneers using polyurethane (PUR) (Lavalette et al 2016;Makomra et al 2020). This material forming method could be used to fabricate curved panels for automotive parts or to mold directly boat structures.…”

“…Vacuum drying with cycles of drying and humidification has been proposed as one of the solutions to minimize crack formation. These cycles activate the viscoelastic and hygroelastic relaxation phenomena so that the stresses due to wood shrinkage do not cause damage (Makomra et al 2020).…”

Mechanical Qualification of Green Glued Laminated Timbers From the Congo Basin Towards Preservation of Forest Species Diversity

“…Nevertheless, investigations were not conducted at the scale of the product. At the industrial level, the green gluing technique may allow some energy saving and reduce the degradation of material integrity (Makomra et al 2020). On the other hand, green wood machining is easier to process than dried wood.…”