Smart glass epoxy laminates with embedded ti-based memory alloy

IFOS, Ecole Centrale de Lyon, 36 avenue Guy de Collongue, 69131 Ecully Cedex, France E-mail: michelle.salvia@ec-lyon.fr

Abstract

Growing attention has been given in the last years to the development of smart materials and structures. Among them, composite materials play evidently a leading role. Actually, it is relatively easy, taking in account their processing techniques, to embed in the structural material itself some sensors, processors and actuators at a mesoscopic scale. Shape memory alloys (SMA) are particularly lilted as actuators because they can be easily drawn into thin wires and incorporated in polymeric and metallic matrices or in classical fibre epoxy laminate structure. To lest the influence of the materials and processing conditions on the actuation properties of adaptive hybrid composites, a model system based on a glass epoxy laminate with embedded wires of a shape memory Ti-Ni-Cu alloy was processed.

Using the Vicotex XE12 prepreg tapes, four sets of asymmetric composite systems have been realized, by prepreg lay up and vacuum bag moulding. The SMA wires in OWSME or TWSME conditions were incorporated as far as possible away from the neutral plan. These asymmetric hybrid laminate beams were tested in clamp-free conditions. With the actuators heated by Joule effect undergoing a reversible martensite to austenite transformation, reversible bending was induced due to the recovery strain in relation with the shape memory effect. The most important deflection of the host composite was obtained for the material, processed with embedded wires in TWSME conditions. Nevertheless, for samples just prestrained for the OWSME, a self-training effect occurred in relation to the reverse polarised austenite to martensite transformation, during cooling after actuation. In order to follow the phase transitions in the embedded SMA wires, resistance measurements have been realized during actuation. Modelling the macroscopic behaviour in the frame of the unidirectional approach de Liang and Rogers and using metallurgical parameters defined from a Clausius-Clapeyron diagram, a description of the temperature-deflection curves can be obtained. Nevertheless some parameters have to be mastered in order to process real structural parts