Optimized identification of earlywood and latewood stiffnesses in loblolly pine in simulated experiments

Knowledge of local mechanical behaviour of wood is especially important as silvicultural practices are modified to allow wood to compete as a relevant material in high technology applications. Challenges associated with identification of local mechanical behaviour have resulted in simplified test geometries designed to determine one or two constitutive parameters. The objective of this work was to design and simulate an entire experiment developed to simultaneously identify the earlywood and latewood orthotropic stiffnesses in loblolly pine in a single specimen and load geometry. The virtual experiment was capable of evaluating optimal orthotropy orientation for reduced identification errors and indicating most favourable choices for data smoothing filters and identification methodology. Additionally, certain ring spacing and latewood percentages were shown to produce large errors, but those combinations are unlikely to occur naturally. The simulation was able to identify Q11,Q22$$ {Q}_{11},{Q}_{22} $$, and Q66$$ {Q}_{66} $$ with approximately +/- 10%$$ \pm 10\% $$ error; the Q12$$ {Q}_{12} $$ error was larger with more scatter. The methodology presented here contributes to the best practices available for heterogeneous stiffness identification.

Automated summary

This study designed a virtual experiment to simultaneously determine the orthotropic stiffness of earlywood and latewood in loblolly pine, and evaluated the optimal orthotropy orientation for reduced identification errors and choices for data smoothing filters and identification methodology. The results showed that certain ring spacing and latewood percentages could produce large errors, but these combinations are unlikely to occur naturally.