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Moisture driven failure monitoring in wood material: numerical analysis based on viscoelastic crack growth approach

S E Hamdi
  • Fonction : Auteur
Rostand Moutou Pitti
Omar Saifouni
  • Fonction : Auteur

Résumé

Wood is considered as an orthotropic hydro-mechanical material whose mechanical behavior strongly depends on the moisture content and the temperature. Taking into account humidity and temperature variation, the mechanical behavior assessment becomes more complex due to the coupling effect between the mechanical stress and the hydric state (Thermo-Hydro-Mechanical behavior or THM) [1]. The viscoelastic behavior of wood under variable humidity, known as the mechanosorptive behavior, induces different responses in the drying and in the humidification phase. However, in presence of climatic variations, the long terms load and especially the crack initiations, the mechanical behavior of wooden structures is found highly modified. The effects of moisture changes on the propagation of cracks are not yet clearly identified. Therefore, it appears necessary to investigate the influence of the variable environment and crack growth process on the mechanical properties of wood structures. This work completes the numerical results presented during the EUROMECH Colloquium 556 [2] about the effect of temperature variation on viscoelastic orthotropic material like wood. In this work, the temperature is supposed constant in order to investigate the effect of moisture content (MC) on fracture mechanics parameters. The new non-dependent integral A [3] is applied so as so to introducing the both opening and shear mode coupled with (MC) in crack growth process configuration. It is shown that for a stable crack propagation (the energy release rate G is a decreasing function of crack length), crack growth resistance is not constant, but changes with crack propagation (figure 1). The (MC) appears to be responsible for the changes, and leads to the formation of the so-called process zone [4]. The aim of this paper is to investigate the effect of temperature (T) and moisture content (MC) changes on wood fracture properties, focusing on crack driving forces, such as G or stress intensity factor (K). In the coming works, the effects of drying will be investigated in order to simulate the cracks observed experimentally during this phase. Figure 1: Effect of moisture content (MC) variation on G vs. crack length during heating process: ΔT = 10° C (a), ΔT = 30° C (b).
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Dates et versions

hal-01616965 , version 1 (17-10-2017)

Identifiants

  • HAL Id : hal-01616965 , version 1

Citer

S E Hamdi, Rostand Moutou Pitti, Omar Saifouni. Moisture driven failure monitoring in wood material: numerical analysis based on viscoelastic crack growth approach. CompWood 2017 – ECCOMAS Thematic Conference on Computational Methods in Wood Mechanics – from Material Properties to Timber, Sep 2017, Vienna, Austria. pp.187 - 198. ⟨hal-01616965⟩
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