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journal of materials research and technology 2021;14:1630 e 1643
liquids in microcracks formed by chemical and thermal shrinkage, as well as by the effects of warping and interface debonding [24,26]. For solid wood and its derivatives exposed to variations in humidity and temperature, dimensional var- iations with consequent formation of residual stresses are quite common. In pieces where the fibers are unidirectionally aligned, such as solid wood or glued-laminated timber, re- sidual stresses are lower than in products whose fibers are crossed from one layer to another, such as OSB, cross- laminated timber, and plywood [27]. Given many materials applied in engineering and that can be used as constituents of the matrix and reinforcement phases, the mechanical behavior of the composite results from several factors, such as the nature of the components, fiber dimension, manufacturing, curing process, and applica- tion and exposure. In a wide universe of responses, computer models have been an effective and accurate option for esti- mating residual stresses and strains [28]. As finite element method (FEM) applications [29], used the modeling to validate the analytical models formulated to estimate the distribution of residual stresses in prestressed composites. Concerning the analysis of process-induced deformations and residual stresses, composites with curved parts were modeled by [25] and, despite relevant results shown with the adopted model, the need for new studies with more complex implementations was highlighted. Computational modeling is essential to better represent and evaluate the most complex behaviors of OSB panels since it allows concatenating the various factors associated with the workability and efficiency of this wood-based product. The FEM allows considering the particularities of each layer, with their specific properties, such as density, fiber direction, and void percentage, which also significantly influence the modulus of elasticity [30 e 32]. The relationships between properties of a material are commonly assumed for the implementation and adjustment of the numerical model for structural behavior. Based on this proposition, in the evaluation of the stress distribution along the OSB panel thickness [18], adopted the value of modulus of elasticity for each layer of the strands as a variable of the panel density profile. For a more accurate representation of the flexural behavior of wood elements [33 e 36], as wood ex- hibits elastic behavior in tension and elastic e plastic in compression, the models must not neglect the non-linearity of the material due to the crushing of compressed fibers, with consequent yielding. Concerning the wood-based prod- ucts, the non-linearity of the material is treated, and its ap- plications are reported, in several studies [37 e 39]. The use of simplified models, such as linear behavior, can lead to sig- nificant differences between modeling and experimental re- sults. With the FEM to simulate an OSB sandwich panel [40], obtained a value of 6.5% higher for flexural rigidity than that determined experimentally. Because of these considerations, the establishing of a method that makes it possible to obtain the equivalent moduli of elasticity of each strand layer, that is derived from the flexural rigidity obtained by standardized bending tests for longitudinal and transverse directions of an OSB panel, will contribute to the provision of this very essential property for modeling with a multi-layer finite element. The main
1.
Introduction
The development of wood-based products has been pointed to as essential to the sustainability of civil construction charac- terized using renewable resources, and such developments also impact the increase of agribusiness activities due to the cultivation of forests of fast-growing species. Simultaneously, solutions for the use of waste from the wood processing in- dustry are provided, being regarded as a constant trend for new investments and ecological appreciation [1 e 3]. Theme- chanical behavior of products, such as glued-laminated tim- ber, cross-laminated timber, plywood, and oriented strand board (OSB) is strongly influenced by the wood ' s non- homogeneous properties, as well as the adhesive used in the composite production. In the case of the reconstituted wood panel, as particleboards and OSB panels, advances in the study concerning the properties and sustainability of this composite material have shown promise due to a possible composition including the use of waste wood and adhesives free of phenolic components, such as castor oil polyurethane resin [4,5]. OSB panels are commonly produced with three layers of thin wood strands, and the geometry, orientation of these elements, and thickness of each layer of strands reflect the stiffness and strength of the panel [6 e 9]. A wide range of applications for OSB is found in the furniture industry and in civil construction, such as wall panels, roofs, I-joist web, reinforcement of wood truss, and slabs composed of a light- timber frame and OSB [10 e 13]. According to [14,15], OSB panels are manufactured under pressure and heat, with the outer layers generally arranged with longer strands aligned in the long dimension of the panel and, in the core layer the strands are arranged in the perpendicular direction. The densification effect is due to the pressing and high temperature applied in the panel manufacturing process, in which the OSB product is denser than the solid wood that originated the strands and the effectiveness of internal adhesion is greater for hardwoods than softwood species [16]. Additionally, the variation in the matrix density, both in the thickness and panel area, affects the properties of this composite, characterizing it as a mate- rial with complex behavior [17]. OSB is a composite treated as orthotropic [18,19], and, in general, the models for represent- ing its elastic properties consider it in its full panel thickness, and not each layer with respective properties which can be quite different from one layer to another [20]. Therefore, as described by [9], for the determination of the moduli of elas- ticity from the specimens in tests, isotropy is assumed through the thickness of the plate. The characterization of the bending behavior, represented by the moduli of elasticity and rupture, is made by testing two groups of specimens extracted with their long dimensions parallel and perpendicular to the long dimension of the panel [21]. In the manufacturing process of laminated composites, the formation of residual stresses is inherently attributed to fac- tors such as micro and macro-level, coupon-level, and component-level [22], which can cause a reduction in the mechanical performance of the composite produced [23 e 25]. Residual stresses lead to a reduction in the composite ' sservice life, which can be explained by the action of penetrating
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