METHODOLOGY FOR MICROMECHANICAL ANALYSIS OF WOOD ADHESIVE BONDS USING X-RAY COMPUTED TOMOGRAPHY AND NUMERICAL MODELING

Structural performance of wood adhesive bonds depends on their ability to transfer stress across an interface of dissimilar materials, namely cell wall substance and cured polymeric adhesive. The interphase region of the bond consists of cell wall substance, voids, and voids filled with adhesive. In this study, an integrated method to numerically model micromechanical behavior of this system is described. The method includes micro-X-ray computed tomography (XCT) to define the three-dimensional (3D) structure of the bond on a micron scale. Tomography data were used as direct input to a micromechanics model. The model provided a 3D representation of equivalent strain and stress of the adhesive bond under load and, furthermore, integrated the microstructure of the interphase region into the solution. The model was validated using lap-shear test results from the same specimens that were scanned for XCT. Optical measurement and digital image correlation techniques provided full-field displacement data of the lapshear specimen surfaces under load. Model simulation results compared favorably with measured surface displacements with spatial resolution in the micron range. The main advantage of the methodology is the accurate representation of the 3D microstructure of wood and the penetrating adhesive system in the numerical model.