Second order hierarchical sandwich structure made of self-reinforced polymers by means of a continuous folding process

• An efficient manufacturing principle is developed to produce hierarchical structures from a fully recyclable material.
• The proposed manufacturing process can be used for materials that can suffer plastic deformations.
• Thermoplastic hierarchical structures show competitive mechanical performance.
• The investigated all-PET hierarchical structures have good recyclability.

One typical way to obtain higher stiffness and strength to weight ratios within structural applications is to use sandwich structures containing lightweight cellular cores. In this study a novel second order hierarchical sandwich structure and its manufacturing principle are described. The whole hierarchical structure is made of a fully recyclable material – different forms of poly-ethylene terephthalate (PET): PET matrix, reinforced with PET fibres (Self reinforced - SrPET) and PET foam resulting in a recyclable structure. The manufacturing path is developed such that it can be implemented within a continuous production line. Out-of-plane compression test are carried out in order to determine the stiffness and strength properties of the proposed structure. An analytical model is developed for evaluating the out-of-plane stiffness and strength properties and used for investigating the influence of the geometric parameters on the structural performance of the proposed hierarchical sandwich structure.

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