13th International Conference on Fracture June 16–21, 2013, Beijing, China -8- 4. Mechanical tests under variable climate The mechanical test under variable climate conditions is based on a creep loading accompanied by relative humidity changes. This test allows the introduction, in the fracture behavior, effects of the viscoelasticity, the shrinkage or swelling and mechano-sorptive process. In this paper, we focus our investigation of drying process. 4.1. Loading history The association of the mechanical loading with the decrease of the relative humidity requests to introduce the time as synchronization variable. In your case, we choose to load the specimen conditioned in a wet environment (20°C, 85%HR). The loading value is chosen according to a static displacement of 1mm with a displacement speed of 0,5mm/min. At this time, the force is fixed as constant during 10 minutes in order to observe creep response in constant wet climate. The next step is characterized by a drying phase by changing climate conditions at a dry state (20°C, 30%HR). The experimenters expect now the complete collapse of the sample. The Figure 8 summarizes the hygro-mechanical loading. Figure 9. Hygro-mechanic loading history 4.2. Experimental results The force-displacement curve vs time is posted in Figure 10. The graph can be separated in four displacement 1mm force 2min creep state at constant force relative humidity 85%RH 30%RH constant wet climate ? time time time 10min
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