The work carried out involved 1) Manufacturing 2) Material characterisation 3) Development of simulation tools 4) Development of measurement tools.
Several materials were considered for testing and analysis under extreme loadings. Both commercial and new composite material samples were manufactured. A new resin system with a more favourable absorbing energy behaviour compared to a standard aeronautical resin was designed. The use of basalt-fiber composite material to enhance the impact resistance of A/C structures was proposed. Samples and large scale structures were manufactured, successfully tested under extreme dynamic loads.
To characterise these materials, it was necessary to optimize the existing and develop new dynamic material characterisation methods for composite materials. To support the design of future aerospace structures under extreme dynamic loading, significant effort was put in developing material models that can capture how the material breaks, influence of damage on material symmetries, shock wave formation and propagation. For this, rigorous development of a physically based damage model allowing modelling of progressive damage in 3D including damage mode differentiation was performed. Also, meso-scale finite-element based models capable of predicting the failure of composite materials were developed. These models can take into account: non-linear, rate dependent behaviour of the constituents (matrix, fibers/yarns), failure of both the interface between the constituents and the constituents themselves. Composite materials that can be modelled are: unidirectional composites, 2D, 2.5D and 3D woven or braided composites with different fibre architectures. Dedicated algorithms were developed to handle large deformation, complicated failure modes in the following solver Digimat-FE embedded solver, and LS-Dyna. The algorithms for damage evolution within the constituents were fine tuned to optimize the computational time. A number of advances were made in the spatial discretisation development of a novel method for reduction of mesh dependency and treatment of localisation of damage, development of coupled FE-SPH code for modelling impact problems, where a part of the structure is modelled with finite elements and part of the model with the SPH.
To capture extreme dynamic events and understand how the material and structures behave during the impact and associated post-impact damage, several NDT and SHM techniques were developed to detect large extreme loading and post loading caused damages.
