Assessing critical fracture energy in mode I for bonded composite joints: A numerical-experimental approach with uncertainty analysis

The manufacturing process of composite structural components involves the assembly of composite parts using adhesives, which introduces variations in the geometrical and mechanical properties of bonded joints. The fracture energy under mode-I loading (G I c ) is a parameter used to predict crack propagation and evaluate the residual strength of the joint. This work proposes a numerical-experimental procedure to determine G I c in mode I, while considering the uncertainties inherent in the manufacturing process of bonded joints. The proposed procedure employs a three-dimensional finite element model to simulate a double cantilever beam test, using finite element commercial software. The cohesive zone model is applied to simulate the mechanical behavior of the adhesive, and experimental data are used to feed the computational model. A Plackett-Burman design is performed to reduce the number of experiments and evaluate the effect of the main influence parameters. Force-displacement curves are obtained, the compliance-based beam method is applied to determine G I c in mode I, employing both trapezoidal and triangular traction-separation laws. The results are thoroughly examined, taking into account the potential strengths and limitations of the proposed procedure, particularly in its application to predicting the behavior of bonded composite joints under mode I loading conditions. The proposed approach can help to understand the uncertainties effect related to the manufacturing process of bonded joints on G I c values, and improve the reliability of predicting crack propagation and residual strength assessment in bonded joints.