Mechano-sorptive behaviour on crack propagation of notched beams of Okume
Résumé
The paper presents the experimental results of the mechano-sorptive induced cracking process on notched beams of Padouk and Okume. The beams tested have dimensions equal to 160x12x60mm and a notch length of 20mm. The tests were carried out in a temperature and humidity-controlled room. These specimens were tested in 3-point bending for 7 days under an initial stress deduced from a strain rate of 0.30%. At the end of the 7 days, further small stress increments were added to the previous one to accelerate the cracking process. The tests were carried out under a sorption cycle of 45-75% relative humidity and at constant temperature of 20°C. Monitoring of cracking parameters, including crack propagation and crack opening, was carried out using a USB microscope. The moisture content of the specimens was monitored by mass monitoring of control specimens of the same size as those tested. The results show that crack propagation is influenced by viscoelastic and mechano-sorptive effects on the one hand and by mechanical loading effects on the other hand. Crack propagation is greater when mechano-sorptive effects occur, especially during the drying process. It was also observed that crack openings tend to increase during drying and close during wetting. Of the two species tested, it was found that Padouk was the species on which cracking was more significant.