Modeling matrix crack/delamination interaction in a double edge notch tension specimen via a divisible cohesive element with damage state mapping

This work investigates the simulated kinematics of matrix crack/delamination interaction in predictions of damage progression of a double edge notch tension specimen. Based on previous work, a divisible cohesive element (Div-CE) is implemented in a three-dimensional finite-element (FE) framework with the Floating Node Method (FNM). Unlike conventional cohesive elements (CEs), the Div-CE captures the correct kinematics when matrix cracks and delaminations interact.

First, the Div-CE implementation is generalized to prevent artificial healing, which can occur under non-monotonic loading conditions. When elements are split to represent cracks with the FNM, the proposed Div-CE scheme handles the complex partitioning and integration of the resulting cohesive-zone sub-elements. Furthermore, as additional cracks interact and partitions are updated, damage state variables are also updated and mapped to new partitions, which prevents artificial healing, yielding a general formulation. The proposed element formulation is verified using single-element models demonstrating its generality and accuracy.

Second, the approach is applied to the modeling of a double edge notch tension specimen. The results obtained with Div-CEs at the ply interface are compared to those obtained with only conventional CEs, and both are compared to the experiments. Overall, the simulated mechanical response and damage morphology, which exhibited extensive matrix crack/delamination interaction, agreed closely to that which was observed experimentally. Notably, the simulations using Div-CEs produced consistently correct damage morphologies with meshes three times coarser than those performed with conventional CEs. Furthermore, contrary to previous studies, the results obtained suggest that the correct failure morphology can be captured without including shear-nonlinearity.