Concepts towards bio-inspired multilayered polymer-composites

Many materials found in nature show extraordinary mechanical properties, that combine high stiffness with toughness and flaw tolerance. The resilience against damage originates from intricate microstructures, which hinder crack growth. Within this contribution, strategies were explored to replicate the mechanisms found in a type of deep-sea sponge. Guidelines were deduced in order to transfer these concepts to engineering materials. In a first approach, the sponge structure was replicated using microlayer composites of a reinforced matrix and soft interlayers (ILs). Results showed, that matrix layers in this type of architecture needed to be smaller than he inherent defect size in order to maximize the toughness gain. However, despite large improvements in impact strength (factor 4.5), stiffness also suffered severe reductions of up to 90% due to the soft interlayers. Alternatively, fewer but larger layers can be used in multilayer composites. Such structures could achieve increased toughness by a factor of 2.81 while also preserving stiffness. Ultimately, the requirements regarding material composition and layer architecture for effective multilayer structures are summarized.