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Recent research has been focused on developing high-performance sandwich structures using renewable resources. The adoption of bamboo rings as a core material and bio-based adhesives has emerged as a promising sustainable design solution for panel construction. It is therefore critical to conduct accelerated ageing tests on these materials to evaluate the impact of environmental humidity on their degradation and durability. This study assessed the effects of moisture ageing on the physic-mechanical properties of eco-friendly sandwich panels and their constituents (aluminium skins, bamboo ring core and castor oil bio-adhesive). Mechanical evaluations of sandwich panels with compacted and spaced bamboo ring cores were performed under varying humidity conditions. Bamboo rings exhibited variable bulk density due to swelling and loss of organic material over time. They also demonstrated increased compressive properties after 2 years of natural ageing but reduced performance after 30 days at 100 % relative humidity. The mechanical properties of the bio-based polymer were enhanced through water-ageing exposure. Sandwich panels constructed with compacted bamboo ring cores exhibited higher bending properties than those with spaced ring core architecture, with the latter showing failures characterised by a wrinkling effect on both skins followed by debonding.

Despite the extensive research on renewable resources (RR) and their potential applications in composite materials and sandwich structures, there remains a significant dearth of life cycle assessment (LCA) studies that comprehensively evaluate the efficacy of RR in mitigating environmental impacts (EI). To bridge this gap, the present study aims to investigate twelve different designs of sandwich panels, specifically referred to as Fibre Metal Laminates (FML). These FML combine aluminium skins (2024-T3 and 1200-H14), polymer matrices (Epoxy, Polyester, and Castor oil Bio-PU), natural fibres (Sisal, Coir, and Cynodon spp.), surface treatments for aluminium skins (sanding, NaOH, and Washprimer), and treatments for natural fibres (Ground, NaOH-treatment and untreated). A cradle-to-gate LCA is conducted, and the inventories are modelled using the OpenLCA 1.6.3 and ecoinvent 3.9 cut-off regionalized database. EI are evaluated in twelve categories, including climate change, fossil and nuclear energy use, freshwater (acidification, ecotoxicity and eutrophication), human toxicity (cancer and non-cancer), mineral resources use, ozone layer depletion, particulate matter formation, photochemical oxidant formation, and terrestrial acidification. Impact World+ method for Latin America version 1.251 is employed to calculate EI. Nine Eco-efficiency indicators and trade-off analyses are evaluated to gain insights into design decision outcomes. Among the various panels considered, FML12, manufactured with aluminium alloy 1200-H14 treated only with sanding, castor oil biopolymer and untreated coir fibres, present the most consistent eco-efficiency indicators. The reference scenario considers the average characteristics of FML (both environmental and mechanical) for trade-off analysis. Despite the fifty percent chance of better performance, FML12 is the only panel that shows higher mechanical performance and lower EI compared to the reference scenario. The importance of this article lies in the novel results obtained using the proposed eco-efficiency indicators, which can be expanded in further studies on the topic.