Moisture ageing effects on the mechanical performance of eco-friendly sandwich panels made of aluminium skins, bamboo ring core and bio-based adhesives

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.