Passive Safety Improvements in Aircrafts by Innovative Energy Absorbing Devices Designed for Additive Manufacturing

The continuous development of lightweight aircraft’s structures and the need to continuously improve the passive safety for passengers, raise the need of innovative structural solutions and devices for impact energy absorption to protect the occupants [1]. Despite the use of advanced control and active safety systems, aircraft accidents can never be completely avoided. In this perspective, the term crashworthiness encloses the ability of an aircraft's structure and of all its internal components to maximize the passengers protection, reduce possible injuries and experienced loads to survivable levels during the impact events [2]. The concept of passive safety is aimed at identifying how to mitigate the risk of injury or death for passengers through the use of devices and systems with energy absorption characteristics placed in key location of the structure. Since lightness is a key requirement for the aircraft structures, the adoption of lightweight and highly energy-absorbing devices is essential to meet the demands of safety and low weight in such kind of structures. Under such demands, hybrid sandwich structures made using Additive Manufacturing techniques can be effectively introduced in key points of the structure, such as below the passenger seats, as devices with passive safety purposes. Such kind of devices make it possible to combine compactness and lightness with the capability of absorbing high amount of impact energy by triggering plastic deformation and failure mechanisms. In this work, the crashworthiness performances of a composite fuselage barrel section from a regional aircraft have been investigated with the main aim of proposing and analysing the introduction of new passive safety components. In detail, sandwich structures with lattice cores have been added below the seats as devices to improve the passive safety in case of a crash and reduce the loads transmitted to the passengers. The vertical drop test is typically preferred as the main method for investigating the crashworthiness features of the aircraft structures since it represents the most critical situation in terms of damage to the structure and loads perceived by passengers. Accordingly, in this work, a detailed numerical model of the fuselage barrel section structure and of the energy absorbing devices have been developed in the finite element software Ls-Dyna to numerically simulate the drop test phenomenon. A numerical Anthropomorphic Tesh Device has been considered inside the structure and placed on the seat to analyse the accelerations and loads suffered during the impact phenomenon. The data recorded by the dummy during the numerical drop test of the fuselage without the devices have been analysed and compared with the data recorded during the numerical drop test of the structure with the passive safety devices with the aim to prove the effectiveness of the proposed structural solutions for improving aircraft passengers safety.