Impact of mechano-sorptive loading on crack propagation of notched beams of White fir and Okume

The paper presents the experimental results of the crack process induced by viscoelastic effect and mechanical loadings. The notched specimens are White fir and Okume with dimensions equal to 160x12x60mm and notch length of 20mm. These specimens were tested in 3-point bending for 5 days under an initial stress of 80% of the rupture stress. At the end of these 5 days, we applied a second stress corresponding to 100% of the rupture stress. These tests were carried out under a sorption cycle of 45-75% relative humidity and at a constant temperature of 20°C. Monitoring of the crack propagation was performed by using an USB microscope. The results show that the crack propagation is accentuated by the drying effects on the one hand and by the effects of the applied stress on the other hand. The results show that crack propagation is influenced by viscoelastic effects, and by mechano-sorptive effects as shown in Figure 1. The crack propagation is more important when mechano-sorptive effects occur, especially during the drying.