Thermal and damping behaviour of magnetic shape memory alloy composites

Susanne Glock, Véronique Michaud
2015
Journal paper

Single crystals of ferromagnetic shape memory alloys (MSMA) exhibit magnetic field and stress induced strains via energy dissipating twinning. Embedding single crystalline MSMA particles into a polymer matrix could thus produce composites with enhanced energy dissipation, suitable for damping applications. Composites of ferromagnetic, martensitic or austenitic Ni-Mn-Ga powders embedded in a standard epoxy matrix were produced by casting. The martensitic powder composites showed a crystal structure dependent damping behaviour that was more dissipative than that of austenitic powder or Cu-Ni reference powder composites and than that of the pure matrix. The loss ratio also increased with increasing strain amplitude and decreasing frequency, respectively. Furthermore, Ni-Mn-Ga powder composites exhibited an increased damping behaviour at the martensite/austenite transformation temperature of the Ni-Mn-Ga particles in addition to that at the glass transition temperature of the epoxy matrix, creating possible synergetic effects.

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Susanne Glock, Véronique Michaud
2015
Journal paper

Abstract

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https://infoscience.epfl.ch/record/212584?ln=en

About this result

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Composite material

A composite material (also called a composition material or shortened to composite, which is the common name) is a material which is produced from two or more constituent materials. These constituent

Single crystal

In materials science, a single crystal (or single-crystal solid or monocrystalline solid) is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of t

Shape-memory alloy

In metallurgy, a shape-memory alloy (SMA) is an alloy that can be deformed when cold but returns to its pre-deformed ("remembered") shape when heated. It is also known in other names such as memory

Effect of annealing and silylation on the strength of melt-spun Ni-Mn-Ga fibres and their adhesion to epoxy

Susanne Glock, Yves Leterrier, Véronique Michaud, Edgars Sparnins

Single crystals of ferromagnetic Ni-Mn-Ga shape memory alloys show magnetic-field and stress induced twinning, leading to shape memory. Adaptive composites can thus be produced by embedding single crystalline particles or bamboo-structured Ni-Mn-Ga fibres into a polymer matrix. To guarantee a durable performance of these composites, adhesion between reinforcement phase and matrix should be quantified and optimised. The influence of annealing and surface treatment with an aminosilane of melt-spun Ni-Mn-Ga fibres on their strength and adhesion to an epoxy matrix was investigated using single fibre tension and fragmentation tests. Annealing of the melt-spun Ni-Mn-Ga fibres changed the surface from a "pimpled" to a smooth microstructure. This resulted in a reduced adhesion of the annealed fibres in comparison to the as-spun fibres embedded in an epoxy matrix. As-spun fibres exhibited an interfacial shear strength (IFSS) comparable to the shear strength of the epoxy matrix so that the silylation did not change the adhesion significantly. For the annealed fibres, the silane treatment improved the IFSS by 67%. Furthermore, the silylation increased the fracture strength of the Ni-Mn-Ga fibres due to surface flaw healing or forming of a protective surface coating. (C) 2014 Elsevier Ltd. All rights reserved.

2014

Magneto-mechanical actuation of ferromagnetic shape memory alloy/epoxy composites

Luis Pablo Canal Casado, Susanne Glock, Véronique Michaud

Ferromagnetic shape memory alloys (MSMA) exhibit magnetic field- and stress-induced twinning when processed into single crystals, but are brittle and difficult to shape. Embedding slender single crystalline MSMA elements into a polymer matrix can thus provide composites with adjustable magnetic strain actuation behavior. Ni-Mn-Ga single crystalline rods were characterized for their magneto-mechanical behavior and embedded in two different types of epoxy matrices with different volumetric fractions. The magnetic actuation of the composites was measured and shown to depend on the Ni-Mn-Ga volumetric fraction and the matrix stiffness. This behavior was well predicted by finite element simulations of the composite using a simple material model for the strain of the MSMA as a function of the magnetic field and applied stresses. Guidelines for composite behavior prediction could thus be proposed. (C) 2015 Elsevier Ltd. All rights reserved.

2015

Structural, physical and damping properties of melt-spun Ni-Mn-Ga wire-epoxy composites

Susanne Glock, Véronique Michaud

Ni-Mn-Ga is a ferromagnetic shape memory alloy that exhibits large, magnetic-field- and stress-induced strains via energy dissipating twinning when processed into single crystals. Grain boundaries suppress twinning and render polycrystalline Ni-Mn-Ga brittle. Ni-Mn-Ga/polymer composites overcome the drawbacks of polycrystals and could thus provide a less expensive and easier to handle alternative to Ni-Mn-Ga single crystals for damping applications. Ni-Mn-Ga wires were produced by melt-spinning and were polycrystalline in the as-spun state. Annealed wires were ferromagnetic at room temperature with non-modulated martensite and a bamboo microstructure. The annealed wires displayed a hysteretic stress-strain behavior typical for twinning. Ni-Mn-Ga wire-epoxy matrix composites were fabricated with as-spun and annealed wires. The damping behavior of annealed Ni-Mn-Ga wire-epoxy matrix composites was higher than that of as-spun Ni-Mn-Ga wire-epoxy matrix composites and of pure epoxy. (C) 2014 Elsevier Ltd. All rights reserved.

2014