Proposal of a model for estimating the tensile strength of hardwoods depending on fiber orientation angle

Abstract

Due to the anatomical complexity and intrinsic variability of properties found in the same species, wood is treated as an isotropic material by various normative codes, where the strength and stiffness values are determined by the strength of materials. The lack of experimental information combined with the lack of knowledge on using strength criteria for anisotropic materials increases the uncertainties in the analysis of structures failures with regards to estimating strength and stiffness properties depending on fiber orientation.  To address this issue, empirical models have been developed and incorporated in several Brazilian and international normative documents. Those models are adjusted according to an exponent (n) that provides the best fit, however, even in the case of the same model, there are still differences regarding the use of this exponent. Hence, the aim of this study is to propose a model to estimate the characteristic off-axis tensile strength value (f_tθ,k), as well as to compare it with empirical models from the literature (with the optimal adjustments of exponent n), making it possible to highlight the best fit. The results showed that the model developed in the research study was the most accurate.