A strategy for efficient modelling of composite delamination in large structures

ENG- Delamination, the separation of composite laminate layers, is a major issue in industries using fibre-reinforced polymers, such as airliners, automobiles and wind turbines. While existing numerical models can accurately simulate delamination, their high computational cost limits large-scale applications. Traditional modelling uses a layerwise approach with fine refinements, increasing computational demand. This research presents a more efficient strategy using an adaptive framework. The model starts with a single element for the laminate’s thickness, adding refinements only where delamination occurs. This approach reduces unnecessary computational effort. A key challenge is detecting the onset of delamination in unrefined models. To address this, a new method reconstructs out-of-plane stresses across the laminate thickness, which is initially modelled with a single element. Once a crack is introduced adaptively, its growth must be modelled using large elements (e.g. 5 mm). An energy-based criterion (Virtual Crack Closure Technique) is coupled to a novel cohesive law modelling the crack advancement while dissipating the fracture energy. A new algorithm extends the energy-based growth criterion to distorted meshes and enables the modelling of complex delamination fronts. Used separately in industry, the stress reconstruction method helps identify high-stress regions in large structures for more detailed analysis, while the energy-based cohesive model enables fast damage tolerance assessments. When combined, these innovations form a novel modelling strategy tailored for large structures. A proof-of-concept test demonstrates that the computational cost is drastically reduced while maintaining accuracy. This research benefits industries relying on composite structures. In aerospace, faster delamination modelling reduces development costs. In automotive applications, it supports the adoption of lightweight composites, improving the energy efficiency of the vehicles. For these reasons, this thesis contributes to the energy transition towards lower greenhouse gas emissions