ABSTRACT
This study presents a new ultra-high temperature composite fabricated by using zirconium diboride (ZrB2), silicon carbide (SiC), and tantalum carbide (TaC) with the volume ratios of 70%, 20%, and 10%, respectively. To attain this novel composite, an advanced processing technique of spark plasma sintering (SPS) was applied to produce ZrB2-SiC-TaC. The SPS manufacturing process was achieved under pressure of 30 MPa, at 2000 °C for 5 min. The micro/nanostructure and mechanical characteristics of the composite were clarified using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and nano-indentation. For further investigations of the product and its characteristics, X-ray fluorescence (XRF) analysis and X-ray photoelectron spectroscopy (XPS) were undertaken, and the main constituting components were provided. The composite was densified to obtain a fully-dense ternary; the oxide pollutions were wiped out. The mean values of 23,356; 403.5 GPa; and 3100 °C were obtained for the rigidity, elastic modulus, and thermal resistance of the ZrB2-SiC-TaC interface, respectively. To explore the practical application of the composite, the natural frequency of an aircraft wing considering three cases of materials: i) with a leading edge made of ZrB2-SiC-TaC; ii) the whole wing made of ZrB2-SiC-TaC; and iii) the whole wing made of aluminum 2024-T3 were investigated employing a numerical finite element model (FEM) tool ABAQUS and compared with that of a wing of traditional materials. The precision of the method was verified by performing static analysis to obtain the responses of the wing including total deformation, equivalent stress, and strain. A comparison study of the results of this study and published literature clarified the validity of the FEM analysis of the current research. The composite produced in this study significantly can improve the vibrational responses and structural behavior of the aircraft's wings.
ABSTRACT
This study investigated the pull-out resistance of superelastic shape memory alloy (SMA) short fibers in mortar with consideration of various end-anchorages that provide different anchoring actions. For the purpose, four types of SMA fibers were prepared using NiTi SMA wires with a diameter of 1.0 mm and the following four end shapes: straight (ST), L-shaped (LS), N-shaped (NS), and spearhead-shaped (SH). The straight-ended fiber was a reference with no working on the end, and the fiber with the spearhead-shaped end was crimped to make the end part flat. The fibers with L- and N-shaped ends were bent with single or double bending. The results showed that only the spearhead-shaped fibers showed self-centering behavior because of the superelasticity of the SMA after slip occurred. This paper discusses the reasons that the ST, LS, and NS fibers do not show self-centering behavior and proposes a concept to induce superelastic behavior in SMA fibers in mortar or concrete.
