Explore the vast range of titles available.

The sustainability evaluation of engineering processes and structures is a multifaceted challenge requiring the integration of diverse and often conflicting criteria. To address this challenge, Multi-Criteria Decision-Making (MCDM) methods have emerged as effective tools. However, the selection of the most suitable MCDM approach for problems involving multiple criteria is critical to ensuring robust, reliable, and actionable outcomes. Equally significant is the choice of a proper normalization technique, which plays a pivotal role in determining the robustness and reliability of the results. This study investigates the impact of common MCDM tools on the decision-making process concerning diverse aspects of sustainability. It also examines how different normalization methods influence the final outcomes. Sustainability in this context is understood as a trade-off among five key dimensions: performance, environmental impact, economic impact, social impact, and circularity. The outcome of the MCDM process is represented by an aggregated metric, referred to as the Sustainability Index (SI). This index offers a comprehensive and robust framework for evaluating sustainability and facilitating decision-making when conflicting criteria are present. To assess the effects of implementing different MCDM and normalization choices on the sustainability assessment, a dataset from the aviation sector is employed. Specifically, a typical aircraft component is analyzed as a case study for holistic sustainability assessment, utilizing data that represent the various dimensions of sustainability mentioned above, for this component. Additionally, the study investigates the influence of initial data variations and weight variations within the MCDM process on the results. The results indicate that, overall, the different MCDM and normalization methods lead to similar outcomes when applied to the design alternatives. However, a deeper dive into the results reveals that the weighted sum method, when paired with min-max normalization, appears to be more appropriate, based on the use case involved for the present investigation, due to its robustness regarding small variations in the initial data and its sensitivity to large ones. This research underscores the critical importance of selecting appropriate MCDM tools and normalization methods to enhance transparency, robustness, reliability, and consistency of sustainability assessments within a holistic framework.

Climate change and global warming pose great sustainability challenges to the aviation industry. Alternatives to petroleum-based fuels (hydrogen, natural gas, etc.) have emerged as promising aviation fuels for future aircraft. The present study aimed to contribute to the understanding of the impact of material selection on aviation sustainability, accounting for the type of fuel implemented and circular economy aspects. In this context, a decision support tool was introduced to aid decision-makers and relevant stakeholders to identify and select the best-performing materials that meet their defined needs and preferences, expressed through a finite set of conflicting criteria associated with ecological, economic, and circularity aspects. The proposed tool integrates life-cycle-based metrics extending to both ecological and economical dimensions and a proposed circular economy indicator (CEI) focused on the material/component level and linked to its quality characteristics, which also accounts for the quality degradation of materials which have undergone one or more recycling loops. The tool is coupled with a multi-criteria decision analysis (MCDA) methodology in order to reduce subjectivity when determining the importance of each of the considered criteria.

Sustainability represents a key issue for the future of the aviation industry. The current work aims to assess and compare aircraft, under the prism of sustainable aviation. In the proposed approach, sustainability is understood as a trade-off between technological sustainability, economic competitiveness/costs, and ecological sustainability, with the latter also including circular economy aspects. To handle the trade-offs and lead to an effective decision, a multi-criteria decision-making (MCDM) methodology is applied, combining the analytic hierarchy process (AHP) and an appropriate weighted addition model. To demonstrate the proposed approach, a set of commercial aircraft incorporating novel fuel/propulsion technologies are compared and ranked with regards to their sustainability, using the metric of sustainability introduced. The dependency of the obtained ranking on the significance attributed to each of the sustainability aspects considered was also performed and discussed. To verify the reliability of the proposed approach, the obtained results are also compared with those obtained from a popular ranking tool from the literature.

When it comes to achieving sustainability and circular economy objectives, multi-criteria decision-making (MCDM) tools can be of aid in supporting decision-makers to reach a satisfying solution, especially when conflicting criteria are present. In a previous work of the authors, a hybrid MCDM tool was introduced to support the selection of sustainable materials in aviation. The reliability of an MCDM tool depends decisively on its robustness. Hence, in the present work, the robustness of the aforementioned tool has been assessed by conducting an extensive sensitivity analysis. To this end, the extent to which the results are affected by the normalization method involved in the proposed MCDM tool is examined. In addition, the sensitivity of the final output to the weights’ variation as well as to the data values variation has been investigated towards monitoring the stability of the tool in terms of the final ranking obtained. In order to carry out the analysis, a case study from the aviation industry has been considered. In the current study, carbon fiber reinforced plastics (CFRP) components, both virgin and recycled, are assessed and compared with regard to their sustainability by accounting for metrics linked to their whole lifecycle. The latter assessment also accounts for the impact of the fuel type utilized during the use phase of the components. The results show that the proposed tool provides an effective and robust method for the evaluation of the sustainability of aircraft components. Moreover, the present work can provide answers to questions raised concerning the adequacy of the CFRP recycled parts performance and their expected contribution towards sustainability and circular economy goals in aviation.

Eco-design is an innovative design methodology that focuses on minimizing the environmental footprint of industries, including aviation, right from the conceptual and development stages. However, rising industrial demand calls for a more comprehensive strategy wherein, beyond environmental considerations, competitiveness becomes a critical factor, supported by additional pillars of sustainability such as economic viability, circularity, and social impact. By incorporating sustainability as a primary design driver at the initial design stages, this study suggests a shift from eco-driven to sustainability-driven design approaches for aircraft components. This expanded strategy considers performance and safety goals, environmental impact, costs, social factors, and circular economy considerations. To provide the most sustainable design that balances all objectives, these aspects are rigorously quantified and optimized during the design process. To efficiently prioritize different variables, methods such as multi-criteria decision-making (MCDM) are employed, and a sustainability index is developed in this framework to assess the overall sustainability of each design alternative. The most sustainable design configurations are then identified through an optimization process. A typical aircraft component, namely a hat-stiffened panel, is selected to demonstrate the proposed approach. The study highlights how effectively sustainability considerations can be integrated from the early stages of the design process by exploring diverse material combinations and geometric configurations. The findings indicate that the type of fuel used, and the importance given to the sustainability pillars—which are ultimately determined by the particular requirements and goals of the user—have a significant impact on the sustainability outcome. When equal prioritization is given across the diverse dimensions of sustainability, the most sustainable option appears to be the full thermoplastic component when kerosene is used. Conversely, when hydrogen is considered, the full aluminum component emerges as the most sustainable choice. This trend also holds when environmental impact is prioritized over the other aspects of sustainability. However, when costs are prioritized, the full thermoplastic component is the most sustainable option, whether hydrogen or kerosene is used as the fuel in the use phase. This innovative approach enhances the overall sustainability of aircraft components, emphasizing the importance and benefits of incorporating a broader range of sustainability factors at the conceptual and initial design phases.

The current prevailing trend in design across key sectors prioritizes eco-design, emphasizing considerations of environmental aspects in the design process. The present work aims to take a significant leap forward by proposing a design process where sustainability serves as the primary driving force. In this context, sustainability is positioned as a fundamental component to be integrated into the initial stages of design, introducing innovative multidisciplinary criteria that redefine the design paradigm. Within this framework, sustainability is characterized using a comprehensive and quantifiable index encompassing technological, environmental, economic, and circular economy dimensions. To demonstrate the practical application of sustainability as the primary criterion in designing mechanical components, a parametrized finite element model of a composite plate is utilized, integrating both pristine and recycled fibers. Subsequently, a demonstrator derived from the aviation industry—specifically, a hat stiffener—is employed as a validation platform for the proposed methodology, ensuring alignment with the demonstrator’s specific requirements. Various representative trade-off scenarios are implemented to guide engineers’ decision-making during the conceptual design phase. Additionally, the robustness of the aforementioned methodology is thoroughly assessed concerning changes in the priority assigned to each sustainability criterion and its sensitivity to variations in the initial data. The significance of the proposed design methodology lies in its effectiveness in addressing the complex challenges presented by conflicting sustainability objectives. Furthermore, its adaptability positions it for potential application across various sectors, offering a transformative approach to sustainable engineering practices.

This paper proposes a new multifunctional flame retardant carbon nanofiber/glycidyl polyhedral oligomeric silsesquioxane (GPOSS) epoxy formulation specially designed for lightweight composite materials capable of fulfilling the ever-changing demands of the future aerospace industry. The multifunctional resin was designed to satisfy structural and functional requirements. In particular, this paper explores the advantages deriving from the combined use of GPOSS and CNFs (short carbon nanofibers) to obtain multifunctional resins. The multifunctional material was prepared by incorporating in the epoxy matrix heat-treated carbon nanofibers (CNFs) at the percentage of 0.5 wt% and GPOSS compound at 5 wt% in order to increase the mechanical performance, electrical conductivity, thermal stability and flame resistance property of the resulting nanocomposite. Dynamic mechanical analysis (DMA) shows that the values of the Storage Modulus (S.M.) of the resin alone and the resin containing solubilized GPOSS nanocages are almost similar in a wide range of temperatures (from 30 °C to 165 °C). The presence of CNFs, in the percentage of 0.5 wt%, determines an enhancement in the S.M. of 700 MPa from −30 °C to 180 °C with respect to the resin matrix and the resin/GPOSS systems. Hence, a value higher than 2700 MPa is detected from 30 °C to 110 °C. Furthermore, the electrical conductivity of the sample containing both GPOSS and CNFs reaches the value of 1.35 × 10−1 S/m, which is a very satisfying value to contrast the electrical insulating property of the epoxy systems. For the first time, TUNA tests have been performed on the formulation where the advantages of GPOSS and CNFs are combined. TUNA investigation highlights an electrically conductive network well distributed in the sample. The ignition time of the multifunctional nanocomposite is higher than that of the sample containing GPOSS alone of about 35%.

Decarbonizing aviation, particularly for long-range operations, is critical for meeting international climate targets, yet it remains technically and operationally challenging. Experimental aircraft (EA) serve to enable flying research infrastructures that provide realistic flight environments for validating emerging technologies and bridging the gap between research and future operational aircraft. While motivated by long-range aviation decarbonization, the study analyses experimental aircraft across multiple scales and missions, focusing on governance structures, funding mechanisms, and business models rather than technical performance metrics. Beyond their technical role, the success and sustainability of EA programs depend strongly on how they are governed, financed, and operated—dimensions that remain comparatively underexplored in the literature, which has primarily emphasized technical performance and flight-test results. To address this gap, this study adopts a structured, multi-method qualitative research approach combining desk-based investigation, a systematic literature review, and comparative case study analysis. The paper reviews and classifies 74 experimental aircraft programs worldwide, with a primary analytical focus on Europe and the United States, examining governance models, funding structures, and business models alongside contextual factors such as platform scale, sectoral orientation, and stakeholder involvement. The results show that most experimental aircraft function as technology demonstration and strategic innovation platforms, supported predominantly by public and public–private funding due to the high-risk and long-term nature of flight research infrastructures. Governance arrangements vary with mission and scale, balancing public oversight, industrial leadership, and academic participation. These findings support the EXAELIA project and provide a reference framework for future experimental aircraft programs.

Designing long-range aircraft for 2050 is a complex, multi-disciplinary challenge requiring integration of technical performance with sustainability objectives, including environmental responsibility, economic viability, circularity, and social acceptance. Existing studies on stakeholder needs in aviation are limited, focusing on specific groups, technical requirements, or individual aircraft concepts, resulting in a fragmented understanding of sustainability-driven needs. This study addresses this gap by systematically identifying stakeholders who influence long-range aircraft development and deriving 191 stakeholder needs, organized into coherent categories spanning manufacturers, operators, passengers, regulators, communities, and energy suppliers. Needs were classified across technical, environmental, economic, circular, and social dimensions, based on a comprehensive review of academic and grey literature, regulatory documents, and industry sources. The resulting framework provides a structured, reproducible approach to support conceptual aircraft design and requirement definition within the European EXAELIA project. By integrating multi-dimensional stakeholder expectations early in the design process, this approach facilitates aircraft development that is technically robust, environmentally sustainable, economically viable, circular, and socially inclusive, demonstrating the value of a stakeholder-driven method for sustainable systems engineering.