Mechano-sorptive behaviour on crack propagation of notched beams of Okume

The paper presents the experimental results of the mechano-sorptive induced cracking process on notched beams of 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 rate of 80% of the failure stress. 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 degrees 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.