Numerical and Experimental Assessment of CFRP-Timber Interface Debonding Using Cohesive Zone Modeling and Full-Field Strain Measurements
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This work presents a numerical and experimental approach for the analysis of debonding mechanisms in CFRP-to-timber bonded interfaces, with emphasis on finite element modeling and full-field validation. Externally bonded CFRP laminates applied to poplar timber elements are studied using a modified single shear test that reproduces combined axial and bending effects representative of real structural behavior. A three-dimensional finite element model is developed using an implicit formulation, where the CFRP and timber substrates are discretized with solid elements and the bond interface is modeled through a cohesive zone model. Damage initiation and propagation are governed by a traction-separation law, allowing simulation of progressive interfacial debonding. The cohesive parameters are calibrated using full-field strain measurements obtained from digital image correlation (DIC) in frontal and lateral views of the specimens. The numerical results show a good agreement with the experimental strain fields, shear stress distributions, and slip evolution for different bond lengths. The simulations accurately capture debonding initiation at the free end of the bonded region and its subsequent rapid propagation, highlighting the influence of bending-induced stresses on interface activation. The proposed methodology demonstrates the predictive capability of cohesive modeling calibrated with full-field experimental data and provides a robust tool for the numerical analysis of CFRP-reinforced timber structural elements.