Synergies of material and geometrical non-linearities allow for the tuning of damping properties of functionally graded composite materials

In this study, we present an alternative fabrication technique to obtain functionally graded polymer–metal composites. The aim is to obtain a composite material with a graded damping factor, which is provided by the presence of pseudoelastic nickel–titanium (NiTi) fibres within an epoxy resin matrix. A preliminary dynamic mechanical characterisation of the NiTi wire revealed a pre-strain dependency of its damping factor. By fabricating wires with curved geometries in the free state, we were able to obtain fibres with a graded level of pre-strain when straightened. This feature in turn imparts a graded damping response. When encapsulating the straightened fibres in an epoxy resin, the graded damping response is transferred to the composite.