Albert Turon

Global/local analyses are formulated within a framework that incorporates responsesensitivity computations. Sensitivity information is exchanged between the globaland local models to recover the first-order response of the corresponding monolithicformulation. To this end, a loosely coupled partitioned strategy is integrated intoa direct differentiation solution scheme. The main contribution of this work is aconsistent procedure for transferring sensitivities across the global/local interfacewhile preserving first-order coupling between the two models. The resultingalgorithm is assessed through representative structural applications involvingdifferent sources of nonlinearity. The numerical results demonstrate that, providedan appropriate time-increment strategy is adopted, local nonlinearities can beisolated and solved within a partitioned framework without compromising the consistency of the linearized response with respect to the parameters of interest.

A design-differentiable global/local framework with adaptive remeshing is proposedfor the analysis of composite structures exhibiting localized nonlinearities. The methodology combines a partitioned solution strategy with an evolving local model, allowing high-fidelity resolution to be introduced only in regions where damage develops, while retaining a low-fidelity global representation elsewhere. The adaptive strategy is driven by the growth of the damaged region. A reference refined mesh is employed to efficiently extract new local elements, while consistent coupling between global and local models is ensured. The extension of the Direct Differentiation Method to the proposed framework is implemented, enabling the efficient computation of sensitivities within an adaptive framework. To address the limitations of standard linearization near limit points, a restart strategy is introduced, improving the accuracy of sensitivity predictions for finite perturbations under strong nonlinearities. The proposed methodology is assessed through several numerical examples involving damage initiation and propagation in composite specimens. The results demonstrate good agreement with full high-fidelity simulations while significantly reducing the number of degrees of freedom. Accurate sensitivity predictions are obtained when compared to finite difference solutions. The framework shows robustness across different structural configurations, highlighting promising applications to large-scale simulations of damage in composite structures.

Global/local analyses are formulated within a framework that incorporates responsesensitivity computations. Sensitivity information is exchanged between the globaland local models to recover the first-order response of the corresponding monolithicformulation. To this end, a loosely coupled partitioned strategy is integrated intoa direct differentiation solution scheme. The main contribution of this work is aconsistent procedure for transferring sensitivities across the global/local interfacewhile preserving first-order coupling between the two models. The resultingalgorithm is assessed through representative structural applications involvingdifferent sources of nonlinearity. The numerical results demonstrate that, providedan appropriate time-increment strategy is adopted, local nonlinearities can beisolated and solved within a partitioned framework without compromising the consistency of the linearized response with respect to the parameters of interest.

As the world moves toward low-carbon aviation, hydrogen has emerged as a leading candidate to replace conventional fossil fuels, offering the promise of zero-emission flight. However, one of the challenges preventing its widespread adoption is its storage. As it is the smallest and most elusive molecule, it easily permeates materials, particularly composites, where damage can create microscopic pathways for leakage. This study introduces a modelling strategy to simulate hydrogen permeability in composite laminates, considering the role of microscale defects and inter-fibre cracks. The method integrates a coupled mechanical-permeability simulation framework that combines Fickian diffusion and Darcy-type flow. Continuum Damage Mechanics is correlated with the permeability and diffusion coefficients, establishing a novel link between crack opening displacements and permeability, a concept not previously extended to gas leakage modelling. The study incorporates the analysis of the influence of ply thickness and crack density. The results indicate that thin plies function as a barrier to leakage by delaying its onset. Experimental permeability data for helium available in the literature provide support for the validity of the proposed methodology.