STUDYING THE FRACTURE OF TROPICAL WOOD SPECIES WITH THE GRID METHOD

Abstract : The present study consists in studying the initiation and propagation of cracks at room temperature of three tropical species: Okume (Aucoumea Klaineana), Iroko (Pterocarpus Soyauxii) and Padouk (Malicia Excelsa). A short review of the literature shows that only few studies dealing with the fracture mechanics properties of this type of wood species are available. Similar studies are however routinely performed on temperate wood species such as Beech and Douglas, using mixed-mode crack growth (MMCG) specimens for instance [1, 2]. In this paper, tropical wood specimens are studied using the grid method [3] and such MMCG specimens, but made of the three aforementioned tropical species. This paper describes the wood specimens, which are subjected to an opening mode, the experimental device and the background of the grid technique used for tracking the location of the crack tip during the test. The origin and characteristics of the tropical wood species studied here are also given. The experimental results are given and compared in terms of force-displacement curves, but also in terms of energy release rate-crack length curves. Typical MMCG specimens made of each of the three different species are shown in Figure 1. The main difference between the three species is their density: Okume (density = 0.44) is less dense than Iroko (density = 0.64) and Padouk (density = 0.79). For all the specimens, the initial crack length is the same: a=20 mm. It is located at mid-height and oriented along the fiber direction, which is horizontal here. The initial crack is completed by a notch (length: 2 mm) made with a cutter in order to initiate correctly crack propagation. A grid, with a regular pitch of 200 microns, was transferred on one face of the specimens, see Figure 1 (d). The technique presented in [4] is used for this purpose. Figure 1. Wooden specimens: Okume (a), Iroko (b), Padouk (c) and the specimen Iroko equipped grid (d). The experimental device is shown in Figure 2. A 200 kN Zwick / Roel testing machine was used for the tests. A camera was fixed on a tripod at a distance of 67.5 cm from the specimens in order to take images of the grid during the tests.
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Soumis le : jeudi 7 décembre 2017 - 09:34:07
Dernière modification le : jeudi 11 janvier 2018 - 06:28:14

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B Odounga, R Pitti, Evelyne Toussaint, M Grédiac. STUDYING THE FRACTURE OF TROPICAL WOOD SPECIES WITH THE GRID METHOD. SEM (Society for Experimental Mechanics) Annual Conference, Jun 2017, Indianapolis, United States. 〈hal-01657721〉

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