Ultrasonically welded eco-friendly sandwich panels based on upcycled thermoplastic core: An eco-mechanical characterisation

A structure's sustainability depends not only on its components, but also on the manufacturing process. The adhesive layer mostly increases the structural weight, reducing weight-specific properties, beside hindering its disassembly and sorting at end-of-life. This study investigates an alternative joining method based on ultrasonic welding for upcycled honeycomb core sandwich panels. Thermoplastic composite skins, reinforced with flax or glass fibres, are connected to an upcycled polyethylene core made from disposed bottle caps and tested under quasi-static and dynamic loads. A life cycle assessment evaluates the environmental benefits of skin/core welding compared with adhesive bonding. Welded panels made from similar skins and cores presented similar to higher weight-specific flexural properties of adhesive-bonded structures (up to 45 % increase), while specific energy absorption under impact is increased by up to 23 % with welded joints. Skin/core welding reduces the panel environmental damage by up to 71 %, with an increment of up to 130 % in its eco-mechanical efficiency.