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journal of materials research and technology 2021;14:1630 e 1643
panel, should be evaluated as accurately as possible for any position of the panel ' s layer.
4.
Conclusions
In this study, exploring results of static bending tests of OSB panel specimens manufactured with balsa wood waste and organic adhesive (Pu-castor oil resin), a method has been established to obtain the equivalent moduli of elasticity to each panel layer. The method was consolidated by a system of equations derived from geometric and elastic parameters. To adjust and validate the model, the FEM was used to evaluate the deflections and shown excellent results, including in predicting the deflections of OSB panels manufactured with another material composition (wood species and phenolic resin). Because of the non-linearity of the material, the main dif- ferences found between the computational modeling results and the deflection experimental results were better treated with multi-linear function adjustments for the stress e strain relationship. It is suggested that the elastic-linear behavior is allowed up to the values close to 60% of the ultimate stress. In the models adjusted for layered simulation, with the initial yield point and total yielding stress modified by the ratio of the moduli of elasticity equivalent and experimental, the differ- ences in the normal bending stress were stronger from the elastic e plastic phase. This makes it possible to consider that the adjustment of the behavior of non-linearity can be improved by other parameters of the material not addressed in this stage of the research. In this sense, it is suggested that further research be developed with approaches and treat- ments for models that can also assess the effects of residual stresses, with the features of this material. The computational modeling with the application of layer properties benefited the obtaining the results for the stress analysis, with details for any position within the thickness of the panel. It is a required application in designs to evaluate the agreement of mechanical performance standards for this type of material. The method established for calculating the equivalent moduli of elasticity, based on the results of the static bending test and with the applied adjustment to the non-linearity, evidenced a good agreement to assign these properties to OSB panel layers.
Fig. 16 e Normal bending stress versus load e ST specimen, with single-layer and layered models.
remarkably similar to what happened for the longitudinal direction. For direction Z (Fig. 14(c-d)), the maximum tension and compression stress obtained was 1.6 MPa. In the ST specimen modeled with Mult_layer (Fig. 15), the maximum stress occurred on the faces of the core layer. This understanding of the stress distribution, especially on the transition surfaces, can be useful for the analysis of the failure in the interface of the layer. In this region, with an equivalent modulus of elasticity ratio of 0.2% ( E TL / E LL ), and for the maximum bending load, from the core to the outer layer, the stress varied abruptly by 204% (24.13 e 7.93 MPa) and 269% (5.02 e 1.36 MPa), in directions X and Z, respectively. The effects of the non-linear model applied for the dis- cretized layers impacted the normal bending stress obtained for each step load (Fig. 16), being significant for the more advanced step loads. For the maximum bending load, the reduction in the normal stress was 24.9% (direction X) and 13.4% (direction Z). For both specimens, the greatest differences between the single-layer and layered models were registered for load in- tensity closer to the maximum value, being affected by the model adopted for non-linearity. This suggests that other considerations and adjustments may be implemented in future studies. The values of the maximum normal stress calculated from the results of bending tests, 32.9 MPa (SL) and 12.7 MPa (ST), as well as the stress estimated by the computational models, 27.3 MPa (SL) and 10.6 MPa (ST), showed that the panel man- ufactured with balsa wood waste with Pu-castor resin (the content of 13%) meets the minimum requirements standard- ized by [47] for OSB/1 panels (for general uses in dry envi- ronments, including use as furniture). For this type of OSB panel, the minimum moduli of elasticity of 20 and 10 MPa are established, in the respective longitudinal and transverse di- rections to the panel. Additionally, the equivalent moduli of elasticity method should also be investigated in future studies to evaluate the efforts in panels manufactured with densities and types of adhesives, different from one layer to another. To specimens cut from the layers of panels thus constituted and tested by tension [20], was obtained maximum stress to the outer layers 2.43 times greater than that of the inner layer. This difference, which can be decisive in checking the maximum load of the
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors thank FAPESP (ordinance 2017/18076-4). Coor- denac¸ ~ ao de Aperfeic¸oamento de Pessoal de N´ıvel Superior e - Brazil (CAPES) e finance code 001. CNPq (ordinance 372
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