Abstract

CAMPO-CEBALLOS, Diego Andrés; LEVY-NETO, Flaminio  and  ROCHA-LIMA, Emanuelle Pacheco. THERMOMECHANICAL RESPONSE OF A VISCOELASTIC NI-TI - SHAPE MEMORY ALLOY COMPOSITE BEAM. Iteckne [online]. 2019, vol.16, n.2, pp.118-125. ISSN 1692-1798.  https://doi.org/10.15332/iteckne.v16i2.2355.

This investigation is concerned with the mechanical behavior of Shape Memory Alloy Hybrid Composite Beams (SMAHC), that consist of a circular bar of Ni- Ti alloy incorporated in a 500 mm long cylindrical pipe of polypropylene (PP), with external diameter 50 mm and nominal wall thickness 7 mm, wound with a nylon/epoxy layer. The Ni-Ti alloy was characterized using: scanning electron microscopy (SEM); X-ray diffraction (XRD) and Differential thermal analysis (DSC). The nominal chemical composition of the alloy is 50.05%Ni / 49.95%Ti, and the softer martensite is the predominant phase at room temperature. The approximate martensite (M) to Austenitic (A) phase transformation temperatures were Mstart = 32°C, Mfinal = 46°C, Astart = 38°C and Afinal = 60°C. For temperature T<Mfinal, Ni-Ti bar presents 100% martensitic phase, whereas for T>Afinal it is fully converted in the Austenitic phase; and its elasticity modulus increases by a factor up to three times. This significant change in stiffness of Ni-Ti, without changing its mass, has motivated the application of such alloy in machine vibration control. The SMAHC beams were subjected to static three-point bending tests, in the elastic regime. Experimental results showed that, in average, at 21°C, the PP pipes effective flexural elastic modulus increased 112%, from 757 MPa to 1609 MPa, when the Ni-Ti bar and the external layer of nylon/epoxy were incorporated to the PP pipe, creating a smart beam. These last results indicate that the SMAHC beam can work as an adaptative structure.

Keywords : Adaptative composite beams; vibration control; NITINOL.

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