Passive damping of composites with embeddedshape memory alloy wires

摘要

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 samediameter of 203 μm, were considered, one superelastic at room temperature, the other one martensitic. For the first one, amartensitic transformation was induced by applying a pre-strain of 2.5% before embedding the wires. The coexistence ofaustenite and martensite should provide damping through the mobility of boundaries between the two phases. For thesecond 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 testson composite plates, neat or with 5% of volume fraction of SMA wires. Resonance frequency and damping ratio weremeasured as a function of temperature. Improvement in damping was verified, at room temperature, for both types ofSMA wires and was observed to be dependent on vibration amplitude. For small-amplitude free vibrations, pre-strainedsuperelastic wires presented more interest as they provided a damping increase of around 87%. The effect howeverdepends on temperature.