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Experimental Fracture Analysis of Tropical Species Using the Grid Method

Bernard Odounga
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Rostand Moutou Pitti
Michel Grediac
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The fracture processes of three tropical species: Aucoumea klaineana, Malicia excelsa and Pterocarpus soyauxii, 6 are investigated with the grid method. These species are widely used in many subtropical countries, in timber building 7 construction, as well as in semi-finished products and paper fabrication. However their fracture behaviour must still be 8 investigated, data being scarcely available on this subject. Modified Mixed Mode Crack Growth specimens are used in order 9 to obtain a stable crack growth evolution in opening, shear and mixed mode ratios. The images of the grid are analysed to 10 provide the crack opening displacement and the crack tip location. The stress intensity factors and the critical energy release 11 rates for each species are then obtained by using the compliance method in imposed displacement. The semi-experimental 12 energetic method is also applied in order to show the efficiency of the proposed technique to characterize the fracture 13 properties of the tropical species under study. 14 Keywords Mixed mode crack growth • Tropical wood species • Compliance method • Grid method 15 2.1 Introduction 16 Today, wood is one of the solutions that sustainably limits global warming of our planet AU1. In Central Africa and particularly in 17 equatorial regions, the forest plays a key role in this regulation. In the case of Gabon, the recent decision of stopping the 18 exportation of tropical species has opened the way to their local extension and to their more widespread use in local 19 individual and industrial buildings. However, the mechanical behavior of local species largely depends on temperature and 20 humidity variations, which can impair their structural efficiency, and thus lead to sudden failure during their service life. 21 Studying failure of tropical wood is crucial to know their behavior and guide local people in their choice of building 22 materials other than concrete and steel. This would also contribute to the sustainable development discussed during the 23 COP21 meeting in Paris last year [1]. 24 This paper is focused on the study of the initiation and the crack propagation at room temperature of the following tropical 25 species: Iroko (Pterocarpus soyauxii), Padouk (Malicia excelsa) and Okume (Aucoumea klaineana). A short review of the 26 literature shows that few studies and data related to failure of this type of wood material are available. Similar studies 27 deal with temperate species as Douglas, Maritime pine and Abies Alba mills, using Compact Tension Shear (CTS) 28 specimens [2–4], Double Cantilever Beam (DCB) specimens [5], Mixed Mode Crack Growth (MMCG) [6] specimens 29 and TDCB specimens [7]. In the present work, tropical wood specimens are investigated with the grid method [8–11].
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hal-01616933 , version 1 (15-10-2017)



Bernard Odounga, Rostand Moutou Pitti, Evelyne Toussaint, Michel Grediac. Experimental Fracture Analysis of Tropical Species Using the Grid Method . Fracture, Fatigue, Failure and Damage Evolution, Proceedings of the 2016 Annual Conference on Experimental and Applied Mechanics, 8, pp 9-14, 2016, ⟨10.1007/978-3-319-42195-7_2⟩. ⟨hal-01616933⟩
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