Properties relationship evaluation and plasticity analytical model approach for Brazilian tropical species

In anisotropic materials such as wood, different responses to bending induced stresses could be expected. This study evaluated the behavior of properties of modulus of rupture (MOR) in bending, the tension strength parallel to grain and the compression strength parallel to grain of Brazilian tropical hardwood species in accordance with Brazilian, European and International Standards, and an analytical equation considering plasticity in the compressed region. Experimental data were obtained using clear wood specimens and tests on ten species. An analysis of the mechanical behavior was conduced for three strength relationships: bending to compression, bending to tension and tension to compression. Linear regression models were determined using the 5th percentile and compared to the ones found by the standards cited. The experimental results were also evaluated to an analytical equation modified from the moment equilibrium of a cross-section. Of the equations evaluated in this study, the ones suggested by the European and International standards for tension strength from bending strength were the ones which best estimated the 5th percentile on experimental data. Other relationships did not show a good agreement with the equations. The analytical equation used had a mean model error 37.4% higher than the experimental values for the prediction of the ratio of tension to bending strength.