Mode I fracture of tropical woods using grid method

Abstract

The cracking properties in opening mode of three tropicals species from the Gabonese forest, namely Iroko (Milicia Excelsa), Okume (Aucoumea klaineana Pierre), and Padouk (Pterocarpus soyauxii), were investigated in this study. Various tests were performed at room temperature and for two different thicknesses. A full-field measurement technique, namely the grid method, was used in order to obtain the displacement and strain maps near the crack during the tests. The mechanical parameters, the specificities of the wood species, the Arcan system and the grid transfer method are first described. For all the specimens, the initial crack length was oriented along the fiber direction (RL). The instantaneous failure tests were performed using two types of specimens: the modified Compact Tension Shear (CTS) and the Mixed Mode Crack Growth (MMCG) specimens. The images of the grid were recorded and analyzed to obtain the displacement maps. The crack opening, the location of the crack tip as well as the strain fields on the surface of the specimens were deduced from these displacement maps. The experimental critical energy release rate Gc was evaluated by the compliance method in imposed displacement. In the case of instantaneous crack with CTS specimens, the comparison of the initial value of Gc for all the samples show that this quantity strongly depends on the thickness and density of the species under study. Crack propagation was observed for a thickness equal to 20 mm only. The results of the crack propagation with the MMCG specimens show the same dependence, and confirm the quasi-brittle fracture behavior of Iroko. The experimental results are scattered, but clear trends can be observed concerning the fracture parameters of the in previous studies described in the literature on wood species with wood species under study. The results are finally compared with those given densities similar to those studied here.

Measuring the Cohesive Law in Mode I Loading of Eucalyptus globulus

“…Fracture characterization of wood is of essential importance, especially in the design of timber elements and connections in engineering structures [5,6]. Connections are most particularly some of the most critical parts, as they may lead to a dangerous situation in cases of brittle splitting failure produced by tension perpendicular to the grain.…”

Comparative studies of three tropical wood species under compressive cyclic loading and moisture content changes

“…This M oi is considered as the own dried weight of the specimen. Five specimens of each group of species were selected, for a total of 15 specimens and put in an oven set to be dried at a temperature of 103 ° C (Odounga et al 2018). Before they were dried by the oven, the starting weight of each sample was determined at time t = 0.…”

Mixed mode fracture of some tropical species with the grid method

“…It is worth mentioning that these species are widely used in various types of applications, in building construction, furniture or paper. However, apart from [17,14], there is no paper available in the literature in which the mechanical properties of such species is discussed.…”

“…The Arcan test device described in Ref. [14] was used in this study. The geometry of the Arcan system is such that the test can be performed with different values of α.…”

“…As such, it can be considered as a follow-up of Ref. [14], where only the opening mode was studied. MMCG test specimens made of iroko, okume and padouk are considered here.…”