PSI- Issue 9

Amal Saoud et al. / Procedia Structural Integrity 9 (2018) 235–242 Amal Saous/ Structural Integrity Procedia 00 (2018) 000–000

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2. Materials and methods The experimental work consisted in subjecting thin, notched flat specimens with different cut lengths to Mode II tensile tests. All specimens and the gripping device were specially designed and produced for this research. 2.1. Test material The material used is Moroccan Thuja "Tectracanalis Articulata" and Eucalyptus Grandis. The first species comes from the Middle Atlas plateau (Khemissat region). This tree can develop a magnifying glass which is an excrescence that is located at the neck of the tree and developing in poorly known conditions whose presence is not systematic. In Morocco, Ellatifi (2012) concluded in his thesis work entitled: The economics of forestry and forest products in Morocco: a review and perspectives that Thuja occupies a total area of about 680 000 ha (equivalent to 11.7% of the total area covered by the Moroccan forest) and plays an important socio-economic role in the context of the satisfaction of local needs of riparian populations in terms of rangeland, firewood and miscellaneous service wood. The second species is Eucalyptus Grandis, from Sidi Yahia Gharb, this tree is different from the previous one since it is a broadleaf tree, unlike Thuja, which is a coniferous tree. These trees have no defects or rots. By respecting the various dimensions according to the specifics of the test, the test pieces were made from ridges 25 mm thick; to better approach the material, we performed physical and mechanical characterization tests:  Physical measurements The moisture, the densities and the shrinkage along the three axes are determined on cubic specimens (20 mm × 20 mm ×20 mm) respectively according to standards NF B 51-004, NF B 51-005 and NF B 51-006.  Mechanical measurements The longitudinal elastic modulus E l and the static flexural strength σ fs were determined by 4-point bending tests using prismatic specimens of (20 mm × 20 mm × 360 mm) cut aligned to the three symmetry directions of the wood in compliance with standard NF B51-008and finally Compression tests were carried out to determine the stress at break σ a according to the NF B51-007 standard. Table 1: Main physical and mechanical c characteristics of Thuja and Eucalyptus Grandis. d H g/cm³ db g/cm³ Rv(%) R T (%) R R (%) A E l (MPa) σ a (MPa) σ fs (MPa) Average Thuya 0.68 0.6 4.98 2.9 1.83 0.64 7437 35 82.22 Standard deviation 0.03 0.02 0.46 0.45 0.06 0.11 148.1 0.38 25.93 Average Eucalyptus Grandis 0.58 0.5 15.54 8.95 5.90 0.67 1680 49.03 1215 Standard deviation 0.11 0.11 2.61 1.53 1.34 0.14 267 0.50 30 2.2. Prototype of test specimen used for Mode II study The specimens used were made from Thuya tree and Eucalyptus Grandis logs. These specimens are intended for a mode II failure test. To do this we based on the previous work of the phenomenon as well as experimental devices developed within our laboratory, we ended up developing the test specimen prototype after several attempts and inspired by various devices on chose the geometry shown in Fig 1 whose dimensional characteristics are presented in Table 2