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Elaboration et caractérisation de composites intelligents NiTi/ époxyde : effets de la transformation martensitique sur le comportement mécanique et sur la décohésion interfaciale

Abstract : In this work a near equiatomic NiTi shape memory wire epoxy matrix composite is studied. The NiTi wire in as drawn condition was subjected to three heat treatments in order to prepare the wires with different transformation characteristics. Three metallic moulds were designed for different types of samples, namely pull-out, tensile and heterogeneous test specimens. The composite specimens were elaborated by casting followed by curing and post curing process. The tests were conducted at three temperatures (20, 80 and 90 °C) and at a constant cross-head speed. The single NiTi wire specimens with a long embedded length were subjected to the pull-out test in order to study the effect of martensitic transformation/reorientation on the debonding initiation and also on the debonding propagation. From in-situ observations, the debonding begins from wire entry point and proceeds to the embedded end. It was observed that when no phase transformation occurs in the wire, the debonding propagates rapidly whilst it is slow when there is wire phase transformation or martensitic reorientation. It was found that the debonding rate depends on the displacement rate as well as the length change during phase transformation. It has been experimentally found that, the interfacial shear strength increases when the martensitic transformation takes place. The mechanical behavior of the resin matrix and the effect of test temperature, wire volume fraction have been determined using standard tensile test. The tests have been conduced at three temperatures. It is found that the martensitic transformation occurring in the wire affect the mechanical behavior of the composite specimens. In this way, using the wire with larger transformation stress enhances the composite tensile strength. This is achieved either by increasing the test temperature or by using the wires heat treated at lower temperatures. The tensile strength increases also by increasing the volume fraction of wires. It is proposed that in the composite, the transformation occurs simultaneously at several points that result in intermittent debonded and bonded zones. In this work the samples with complex geometry were designed and fabricated in order to estimate the elastic properties of the composite material in two directions (perpendicular and parallel to the wire axis). The specimens with random speckle were then subjected to the simple loading. The heterogeneous displacement/strain fields generated due to the complex geometry of the composite samples were measured. An inverse method was established in this work and the material parameters were identified. The results were then compared to the results obtained by Mori-Tanaka method. Moreover, the numerical strain fields obtained using the identification parameters was compared to the experimental ones. A good correlation was found in both cases.
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Submitted on : Tuesday, February 8, 2011 - 5:14:50 PM
Last modification on : Friday, August 5, 2022 - 2:54:00 PM
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  • HAL Id : pastel-00564365, version 1


Yousef Payandeh. Elaboration et caractérisation de composites intelligents NiTi/ époxyde : effets de la transformation martensitique sur le comportement mécanique et sur la décohésion interfaciale. Mécanique des matériaux [physics.class-ph]. Arts et Métiers ParisTech, 2010. Français. ⟨NNT : 2010ENAM0032⟩. ⟨pastel-00564365⟩



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