On the effectiveness of double-double design on crashworthiness of fuselage barrel

The increasing use of composite materials in the aviation industry for the manufacture of higher performance components required the introduction of efficient optimisation methods for the design of composite laminates. Metal-replacement with composites provided the first step in the design of higher performance aviation structures. Nowadays, the additional step is to optimise these structures to make them even more performing and lighter. Mass reduction drives the optimization with number and orientation of plies as main parameters. In this perspective, the Double-Double (DD) laminates approach provided an effective method to optimise composite structures for weight reduction and strength purposes, without restrictions on symmetry and orientation angles. Especially for optimized components, crashworthiness remains a key aspect in evaluating the performance of composite aircraft structures, such as for fuselages. In this work, the crashworthiness features and the dynamic response of a regional fuselage barrel section in a vertical drop test has been numerically investigated performing a comparison between a configuration with conventional composite skin and a configuration with optimized and lightened skin through the Double-Double (DD) approach. The comparison proved that the configuration with the optimised skin has been characterised by adequate performance in terms of crashworthiness and passive safety for passengers, when compared to the conventional configuration. The effectiveness of Double-Double method in designing crashworthy composite components has been demonstrated, while simultaneously reducing the structure's total mass and enabling compliance with restrictive fuel consumption and emission regulations. The employment of optimized skin resulted in a total mass reduction for the whole structure up to 34%, due to mass reduction of the skin of 69.8% with respect to conventional configuration.