236 N. Angellier et al. test in variable humidity environment are presented. The last section shows results for two species used in Europe (Douglas and White Fir). Then, these results are discussed: in terms of force-displacement curve for static tests and of crack advance for creep tests. 29.2 Experimental Setup In this section, we briefly describe wood samples and the experimental devices used to characterize the failure process in Douglas and White Fir under several mechanical and hydric loadings. 29.2.1 Sample Preparation The experimental protocols are based on using a Double Cantilever Beam (DCB) with variable inertia beam specimen. The chosen species are Douglas and White Fir. Several samples of each species have been machined in a Radial-Longitudinal (RL) configuration. Samples are conditioned in climatic chambers in which temperature and relative humidity are regulated at 25ıC and 40 % RH or 90 % RH, respectively, corresponding to average moisture content levels around 9 and 17 %. After conditioning, a pre-crack with an initial length equal to 50 mm, is performed along the grain direction with a band saw (3 mm thick). The geometry and loading symmetry allow assuming an open mode configuration according to a particular choice of grain alignment with the crack, Fig. 29.1. Fig. 29.1 Double cantilever beam with variable inertia specimen
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