A computational micromechanics approach to model interlaminar damage migration in composite materials

Since interlaminar damage (delamination) represents a critical failure mode of composite materials, its resistance in multidirectional composite laminates needs to be well understood. Under certain conditions, delamination migration may occur, leading to its relocation from an interlaminar region to another through an intralaminar matrix crack. Computational micromechanics has been emerging as a powerful tool to study the behaviour of heterogeneous materials, providing enough detail to accurately capture certain features that are impossible to do so using higher scale models. Therefore, this project presents a micromechanical finite element (FE) model to study interlaminar damage propagation and migration in composite materials, making use of the FE commercial software Abaqus. Different features that characterise this failure mechanism are successfully modelled and compared with previously conducted experimental observations. It is thus concluded that this computational framework generated in Abaqus is able to simulate interlaminar damage migration, providing a sound tool to better understand the conditions behind interlaminar fracture. Different in-built capabilities of Abaqus/Explicit were used and explored to model these FE micromechanical models, such as:

• Tie Constraints.
• General contact considering cohesive behaviour.
• Damping associated with volumetric straining - Bulk Viscosity.
• Variable Mass Scaling.
• Free tet meshing and advancing front sweep meshing algorithms.
• Enhanced Hourglass Control and element deletion.

The images show the fracture surfaces originated in different multidirectional laminates by using a user defined FORTRAN subroutine (VUMAT) that describes the mechanical behaviour of an epoxy resin, and are compared with Computed Tomography (CT) experimental observations. This work has been published this year (2019) in an international composites journal: https://www.sciencedirect.com/science/article/pii/S0263822318343605