Investigation of nacre as a model for the development of bonded ceramic-polymer composite multilayer materials

Ceramic materials have through their brittle-elastic fracture behaviour today often disadvantages in terms of technical applicability. Inspired by nacre it is attempted to address this fundamental disadvantage and to push the development of ceramic-polymer layer composites. The objective is to provide a novel material with improved fracture toughness compared to previously known ceramic composite materials. Due to the task, this paper is divided into the part of an extensive characterization of nacre and into the section of the development of a ceramic-polymer layer composite. Nacre shows a regular structure of individual aragonite platelets, which are covered by an organic matrix. The different mechanical studies of the natural model show that the enormous increase in fracture toughness compared to the values of the individual components and the large ductility are affected by the intermediate polymer layers. By varying the temperature and humidity conditions of the organic matrix this result is further confirmed. The production of ceramic-polymer layer composites is done by gluing individual thin ceramic sheets with high performance characteristics. The properties of the used polymers plus the material and shape of the ceramic sheets are varied thereby. Tolerant fracture behaviour can be achieved with this new material by a suitable stiffness ratio between polymer and ceramic. The fracture mechanical investigations indicate a significant increase in fracture toughness compared to the single ceramic components. The material develops with increasing crack length even an increase of the crack resistance. With the combination of high hardness and strength of the engineering ceramic and the large elasticity of the adhesives it is possible to develop a ceramic-polymer layer composite, which exhibits improved fracture toughness and is therefore highly resistant to mechanical stress