Passive damping of composites with embedded shape memory alloy wires

Abstract

NiTi alloy wires were embedded during the infusion processing of woven carbon fibre reinforced plastic (CFRP) composite plates with the purpose to passively increase their damping. Two types of NiTi wires, having the same diameter of 203 μm, were considered, one superelastic at room temperature, the other one martensitic. For the first one, a martensitic transformation was induced by applying a pre-strain of 2.5% before embedding the wires. The coexistence of austenite and martensite should provide damping through the mobility of boundaries between the two phases. For the second type of wires, the enhancement of damping was based on the presence of martensite. The passive damping effect produced by the shape memory alloy (SMA) wires was evaluated from free vibration tests on composite plates, neat or with 5% of volume fraction of SMA wires. Resonance frequency and damping ratio were measured as a function of temperature. Improvement in damping was verified, at room temperature, for both types of SMA wires and was observed to be dependent on vibration amplitude. For small-amplitude free vibrations, pre-strained superelastic wires presented more interest as they provided a damping increase of around 87%. The effect however depends on temperature.