Nowadays, the railway industry moves to eco-sustainable solutions to reduce excessive CO2 emissions and energy consumption [
1‐
3]. Innovative solutions were proposed to act directly on the vehicle structure, power train system or control system. Harrison et al. [
4] presented the development of a detailed MATLAB/Simulink model to control a bimodal train. It combined adaptive speed limit control with selective engine shutdown, reducing the carbon dioxide emissions. Great interest is growing in hydrogen power train systems, widely described from many points of views in Reference [
5,
6]. On the other hand, mass reduction of the vehicle structure, through lightweight design approaches [
7], could be an important solution to reduce the required power during running operation conditions. It allows the increasing of the payload, reducing at the same time the rail and the wheel wear so that the damage produced on the track by the train [
8]. Innovative materials and structural optimization processes represent effective tools for achieving this goal. The car body shell is generally made up of metallic components held together by welds and/or bolts and covered using metallic sheets. In some cases, the structure is made up of aluminium extruded components, which are welded together to create the car body cross section. Grasso et al. [
9] proposed three different types of composite panels, tested for innovating a rail vehicle component and carried out an extensive mechanical characterization to assess the mechanical data of lamina. An end car box of a railway vehicle was redesigned introducing carbon fibre composite material [
10]. Compared with traditional metallic materials, the weight of the innovated component was about 72% of the weight of aluminium alloy box, maintaining acceptable tensile, fatigue and impact resistance. Pultrusion manufacturing process were investigated for the fabrication of medium-speed railway vehicle mobile panels for the substitution of steel panels, using glass fibre-reinforced polymers (GFRP) [
11]. The GFRP fabric pultrusion panel design was successful according to the EN12663-1:2015 and the project requirements, achieving a weight reduction of 35.5% respect to the original design. Yang et al. [
12] carried out an experimental and numerical approach for the evaluation of projectile impact behaviour of curved GFRP composites for rail vehicles. Moreover, optimization processes were combined with sandwich structures to improve several different characteristics. With the aim of finding the optimal configuration for composite sandwich structures used in rail vehicle floor panels, in terms of mass and cost, a multiple objective approach was tested [
13]. Various requirements, such as stiffness, strength, buckling and thickness were studied to evaluate their influence in the choice of load carrying sandwich panels for high-speed rail vehicles. Then, they were optimized using a finite element (FE) software achieving a mass saving of 30% [
14]. The composite body shell of a light rail vehicle was optimized combining shape and size optimization, including 96 constraint functions to select for the single panel, supporting a labour-intensive multi-level approach [
15]. Crashworthiness performances of a composite energy-absorbing structure for railway vehicles were optimized by Xie et al. [
16]. Finally, optimization process can be applied singularly on car body metallic structures. Topology, shape and size optimization were combined to innovate the ribs of a railway car body shell [
17], with the aim of reducing mass. Fatigue life prediction was included in a multidisciplinary design optimization method for lightweight car body [
18].
During the present activity, the roof assembly of a light rail vehicle car body has been redesigned for introducing an aluminium honeycomb sandwich panel, using a bonded joint as fastening system. Then, the innovated structure was optimized to reduce the global mass. At this stage of work, the main focus was on the changing in static and dynamic behaviour of the complete redesigned car body, passing from a weld roof structure to a bonded one. Reference European standards for rail vehicle performance evaluation were adopted for testing the car body.
This paper is organized in five sections. In sect.
1, a brief introduction about the application of optimization processes on railway vehicles and some eco-sustainable solutions for car body are included. The proposed methodology is described in sect.
2. The vehicle used as benchmark and the innovation process that involved it are reported in sect.
3. FE structural analysis and application of the optimization approach are explained within sect.
4, where each step has been discussed, including results. Section
5 reports conclusions and future developments of the present activity.