Green and lightweight structures produced by innovative technologies

The present PhD thesis investigates the potential of replacing conventional materials used in industrial applications with sustainable and lightweight alternatives, addressing the growing need to reduce environmental impact and improve resource efficiency. The research focuses on advanced materials and innovative technologies, including sandwich structures, bio-based materials, and additive manufacturing, with the aim of evaluating their applicability. Lightweight design and material sustainability are increasingly critical factors across various sectors, particularly in transport, aerospace, and energy. Composite sandwich structures are widely adopted due to their excellent combination of low density and high mechanical performance. However, end-of-life management remains challenging, as the separation of components and limited recyclability of synthetic matrices hinder sustainable disposal and recovery. To overcome these limitations, this thesis explores sustainable sandwich structures incorporating bio-based polymers or recyclable metal alloys, offering a balance between mechanical performance, reduced weight, and environmental compatibility. The first part of the research focuses on traditional and hybrid sandwich structures, exploring the use of metal and eco-friendly alternatives. An extensive experimental campaign was carried out to characterise their mechanical behaviour under various loading conditions, including quasi-static indentation and low-velocity impact. The effect of indenter geometry was investigated, and a predictive coefficient, the Dynamic Scaling Factor, was introduced to estimate the material’s response to dynamic loading based on simpler and more cost-effective static tests. Comparative analyses were also performed between all-metal aluminium honeycomb structures and conventional materials with equivalent flexural stiffness. Further investigations focused on hybrid sandwich structures, specifically Flax/AHS and Basalt/AHS configurations. The mechanical response of these structures was evaluated under different loading conditions, and failure mechanisms were systematically assessed using visual inspection, radiography, microscopy, and thermography. The second part of the research focuses on additive manufacturing techniques, with particular attention to biodegradable polymeric materials such as PLA and foamed PLA. The study investigates the influence of process parameters on foam morphology, bending and impact behaviour, and failure mechanisms. Foam additive manufacturing is highlighted as a promising approach for producing lightweight, recyclable, and environmentally friendly structures, forming a bridge between theoretical investigations and practical applications for sustainable industrial components. Overall, the results demonstrate that sustainable sandwich structures and PLA-based additive manufactured materials can effectively replace conventional solutions, integrating advanced design, green materials, and modern production technologies. By combining lightweight principles with high mechanical performance and improved end-of-life management, these approaches provide a promising strategy for enhancing industrial sustainability, reducing environmental impact, and supporting circular economy practices across multiple sectors.