A 3D failure criterion for damage assessment in composite T-joints under complex multiaxial stress status

Composite T-joint application as a stiffener is a conjoint aspect in many thin-shell aero-structures; however, these structures are often prone to low-velocity impacts that can drastically reduce their load-carrying capacity. This article implements a new effective approach to determine damage sensitivity and progression. The first part includes a detailed assessment of the three-dimensional (3D) stress status and the result shows that the shear stresses substantially influence the deltoid matrix failure and skin-stiffener debonding. In the second part, a high-fidelity 3D damage model, with a modified damage initiation failure criterion based on Hashin and Puck is implemented via ABAQUS/EXPLICIT VUMAT user-subroutine. The intralaminar damage model considers 3D stress states and continuous stiffness degradation theory while for interlaminar failure, the cohesive-zone method based on bi-linear traction separation law is used. The mechanical response, as well as the intralaminar and interlaminar damage predicted by the model, shows a good correlation with the experimental findings. The results model shows a maximum error of 8% in the case of load versus time and a maximum error of 2.5% in the case of energy absorbed with the experimental results. Overall, the impact behavior of integrated composite structures can be effectively predicted using the recommended method.