A cohesive network approach for modelling fibre and matrix damage in composite laminates

Abstract

In the current study a high fidelity analysis approach is used to predict failure in notched composite structures. Discrete cracking is explicitly modelled by incorporating cohesive interface elements along potential failure paths. These elements form an interconnected network that allows for interaction between interlaminar and intralaminar failure modes. Finite element models of these configurations were created in the commercial analysis software ABAQUS and a user defined material subroutine (UMAT) was used to describe the behaviour of the cohesive elements. The user material subroutine ensured that the model remained stable despite significant damage, which is a significant challenge for implicit damage simulations. Two analysis approaches were adopted using both the as-measured and in-situ ply strengths. Both approaches were capable of closely predicting the mean ultimate strength for a range of hole diameters, however, the measured ply properties resulted in extensive matrix cracking in the surface ply which resulted in a deviation from the experimentally measured surface strain. The results demonstrate that high fidelity physically based modelling approaches have the ability to compliment experimental programs focussed on the design and certification of composite structures.

An Auto-Generated Geometry-Based Discrete Finite Element Model for Damage Evolution in Composite Laminates with Arbitrary Stacking Sequence

“…[33,43,50], Iarve et al [35,51,52] and Van Der Meer et al [34,[53][54][55], are among the early few groups to approach discrete damage modeling in composite laminates. Indeed, Yang is one of the contributors in Augmented Finite Element Method (A-FEM) mentioned above [33,43], which is a essential fundamental of the first type of method (element partitioning), Yang also contributed in the second type of method (element embedding) referred here as work by Joosten et al [47]. Besides the discrete modeling approach with real fracture surfaces, many CDM-based and XFEM-based methods have been intensively modified and developed in-house, thus showing excellent capability and computational efficiency in various applications.…”

“…In another work, Joosten et al [47] applied preprocessing tools to embed zero-thickness elements among structured standard elements to anticipate all three types of failure modes. The embedded elements are not physically created, but instead, are defined and numerically formed by the nodes of priorly-generated ply elements.…”

“…However, since fiber fracture surfaces are orthogonal to transverse matrix cracks, while each ply must have a fiber-aligned mesh determined by its layup angle, this method will inevitably result in small or skewed elements with poor mesh qualities, which consequently results in the inability to generate elements in laminates with arbitrary layup. A possible way to avoid undesirably skewed meshes is to use surface-based contact relations between structured elements of different plies, but as pointed out by the authors themselves [47], displacement jumps may not be represented properly between intra and inter-ply cracks because of the involved master/slave pairing mechanism in the surface-based contact formulations. Actually, the surface-based contact behavior in FEM is based on the interpolation of nodes on the involved surfaces, one of the two is usually defined as a 'slave surface', such that its DOFs follow the other 'master surface'.…”

A Numerical Study on the Influence of Strain Rate in Finite-Discrete Element Simulation of the Perforation Behaviour of Woven Composites

“…Discrete damage modelling using cohesive zone models (CZM) has been used to simulate connections and separations at predefined interfaces to develop models capable of considering stress concentration around crack tips [ 24 , 25 , 26 , 27 , 28 ]. This way, additional degrees of freedom are added to the model by inserting 2D cohesive elements or spring elements at potential crack paths in between solid 3D elements.…”

“…This way, additional degrees of freedom are added to the model by inserting 2D cohesive elements or spring elements at potential crack paths in between solid 3D elements. The solid elements dominate the global response of the model and the cohesive elements are used to assess the initiation and propagation of damage [ 24 ]. Joosten et al [ 24 ] simulated notched composite specimens using a hybrid finite-discrete element model with a combination of solid and cohesive elements to consider discrete cracking.…”