13th International Conference on Fracture June 16–21, 2013, Beijing, China -2- 2. Experimental setup 2.1. Material and methods Experimental tests are based on the use of a double cantilever beam in Douglas fire submitted at a displacement control loading. Two sample groups are conditioned in dry and wet environments, respectively. In the other hand, for initial moistened specimens, a ramp of drying is imposed. All tests are filmed by CCD camera in order to record the crack tip advance. The Douglas fire specimen is a Double Cantilever Beam. Dimensions are fixed in Figure 1. The initial crack is oriented in the longitudinal axis with an initial length of 50mm. Its thickness is 20mm. The loading axes have a diameter of 10mm. The crack propagation is assumed to be in the Radial Longitudinal plane. Figure 1. Double Cantilever Beam geometry Two families of four specimens are placed in a dry (20°C, 40%HR) and wet (20°C, 85%HR) climate corresponding to moisture contents of approximately 9% and 19%, respectively. These specimens are acclimated during several weeks in order to obtain a moisture content homogeneity. The testing machine is a Zwick electromechanic incorporating an environmental chamber allowing the time synchronization between force-displacement and temperature/humidity histories, Figure 2. Figure 2. Zwick electromechanic machine and CCD camera
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