Abstract
Delamination is one of the most prominent damage modes leading to the final failure of laminated composite structures subjected to quasi-static or fatigue loading. Recent trends in high-performance industries call for innovative damage-tolerant designs which allow damage to occur to a certain extent. Such damage-tolerant designs require accurate modelling and simulation tools that are efficient enough to be used on a large scale. Cohesive Zone Models are currently the most used choice for accurate delamination onset and propagation prediction but require a fine discretisation that makes them too computationally demanding for application into large structures.
This thesis presents innovative solutions to the fine mesh burden of Cohesive Zone Models through the use of the Floating Node Method to efficiently and adaptively refine the model, thus lowering the computational requirements of the simulations. The developed formulations can be applied to structures loaded under quasi-static and fatigue conditions. In addition, damage tolerant designs are proposed and studied using the tools developed during the PhD study.
The thesis is organised as a compilation of papers. The first part of the thesis is an introduction to the most important topics of the project. This includes a brief description of laminated composite structures and their progressive damage process, the modelling of delamination using cohesive zone models, the Floating Node Method, and the Matlab Finite Element Analysis code developed for the project. The second part of the thesis is composed of three journal papers.
Paper A presents an adaptive refinement strategy and Floating Node Method based element to refine the mesh depending on the analysis needs. The results show that the presented formulation is more efficient than standard cohesive zone model implementations with the same degree of accuracy. Paper B further develops said formulation to include fatigue loading capabilities, featuring a fatigue Cohesive Zone Model and adaptive formulation capable of modelling several delamination cracks propagating in different directions. Paper C uses the adaptive Floating Node-based formulation with minor modifications to explore novel structural toughening strategies against delamination. Namely, the possibility of using patches of interface toughening or weakening materials to initiate multiple delaminations is explored. By having multiple delaminations, new crack surfaces are created, which means that more energy is dissipated at the same loading level.
This thesis presents innovative solutions to the fine mesh burden of Cohesive Zone Models through the use of the Floating Node Method to efficiently and adaptively refine the model, thus lowering the computational requirements of the simulations. The developed formulations can be applied to structures loaded under quasi-static and fatigue conditions. In addition, damage tolerant designs are proposed and studied using the tools developed during the PhD study.
The thesis is organised as a compilation of papers. The first part of the thesis is an introduction to the most important topics of the project. This includes a brief description of laminated composite structures and their progressive damage process, the modelling of delamination using cohesive zone models, the Floating Node Method, and the Matlab Finite Element Analysis code developed for the project. The second part of the thesis is composed of three journal papers.
Paper A presents an adaptive refinement strategy and Floating Node Method based element to refine the mesh depending on the analysis needs. The results show that the presented formulation is more efficient than standard cohesive zone model implementations with the same degree of accuracy. Paper B further develops said formulation to include fatigue loading capabilities, featuring a fatigue Cohesive Zone Model and adaptive formulation capable of modelling several delamination cracks propagating in different directions. Paper C uses the adaptive Floating Node-based formulation with minor modifications to explore novel structural toughening strategies against delamination. Namely, the possibility of using patches of interface toughening or weakening materials to initiate multiple delaminations is explored. By having multiple delaminations, new crack surfaces are created, which means that more energy is dissipated at the same loading level.
| Originalsprog | Engelsk |
|---|---|
| Vejledere |
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| Status | Udgivet - 2022 |