Development of a hybrid elasto–plastic-damage material model for the analysis of adhesive-free lapped scarf timber joints

This study develops a nonlinear elasto–plastic–damage material model to simulate the mechanical response of adhesive-free lapped scarf timber joints with inclined faces and hardwood dowels. The formulation integrates plasticity and continuum damage to capture progressive stiffness degradation and irreversible deformation in anisotropic wood. A three-dimensional finite element model was implemented in Abaqus through a user-defined UMAT subroutine, employing the Hoffman yield criterion to describe the onset of plastic flow and a damage evolution law to govern stiffness reduction under tensile and compressive loading. The joint configuration, consisting of English oak dowels connecting Norway spruce beams, was analyzed as a representative hybrid arrangement. Calibration and validation against experimental bending tests demonstrate that the model accurately predicts the nonlinear load–displacement response and reproduces key failure mechanisms. The results confirm the effectiveness of the proposed framework in providing reliable numerical analysis for adhesive-free timber joints.