This article describes a structural system identification approach for the characterization of a novel retrofitting textile, the “Composite Seismic Wallpaper.” This polymeric textile was developed within the EU co‐funded project Polytect as a full coverage method for increasing the seismic resistance of masonry structures. Recently, the wallpaper has been full‐scale tested, on a two storey building, at the Eucentre (Pavia) as part of the Seismic Engineering Research Infrastructures for European Synergies (SERIES) program. In this article, an advanced multistage identification methodology is proposed for the successful simulation of this novel material based on the results of the extensive experimental campaign. The identification is essentially formulated as an inverse problem that combines a Genetic Algorithm (GA) as the optimizer and a finite element (FE) model as the physical model of the structure. The aim is material characterization and modeling of the dynamic response of the structure; an issue which is nontrivial due to the intrinsic complexities associated with both masonry and polymers. The process outlined herein is successful in yielding a calibrated model that can more accurately capture the experimentally observed behavior of this three‐dimensional full‐scale test case.

The performance of aluminium welds in rail vehicles under high dynamic loading conditions has been investigated. Aluminium alloy welded joints subjected to dynamic loading can fail by a mechanism of unstable crack growth along the heat affected zone/weld metal interface, a phenomenon commonly known as 'weld unzipping'. Modelling of weld unzipping in large rail structures is a challenging task since it requires knowledge of material tearing instability and material fracture parameters, as well as addressing the problem of mesh resolution, which together pose severe challenges to computability. The proposed methodology for the prediction of weld failure is based on the validation of the numerical models through correlation with laboratory scale tearing tests. The tearing tests were conducted on samples taken from real rail extrusions with the purpose of obtaining the failure parameters under dynamic loading and understanding the effect of weld material composition on joint behaviour. The validated material models were used to construct a finite-element analysis simulation of the collision of an aluminium rail car and investigate the effect of joint geometry on the failure mechanism. Comparisons of the model with the failure observed in an aluminium rail vehicle that was involved in a high-speed collision have shown that it is possible to model the phenomenon of weld unzipping with good accuracy. The numerical models have also been used as a tool for the optimization of joint design to improve crashworthiness. A proposed thickening of the aluminium sheet at the weld region is shown to eliminate the weld unzipping failure mode with the impact energy absorbed by controlled buckling of the structure.

The objective of the study was to characterise the energy absorption of composite panels with tied cores, subjected to a drop weight impact test. Numerical simulations based on explicit finite element analysis have successfully modelled low velocity impact tests carried out on sandwich panels with web-core structure and plastic foam. The numerical model has been validated in terms of the failure behaviour of the panel and the variation of the contact force after the initial peak load corresponding to flexural failure. The numerical model is used for a better interpretation of the test results and of the failure mechanisms within the structure. The contribution to the overall energy absorption of the different parts composing the panels has been studied, with the aim of evaluating the feasibility of using low density foam in combination with web-core reinforcement in structural applications.

The failure behaviour of fibreglass sandwich panels with structured internal cores (z-cored panels) was studied in bending. A finite element model was developed for the simulation of three point bending tests and this has been validated against experimental results. The model was able to predict both the elastic response and, more importantly, the failure behaviour of the structure. It is therefore suitable for use in the optimising the design of z-core sandwich panels for transport applications. The same modelling approach was also applied to the structural behaviour of a larger sandwich panel with a metallic insert which was employed in the design of a semitrailer as part of a demonstration of the viability of the technology.

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