This paper proposes a design of novel composite materials inspired by the Peano curve and manufactured using PolyJet 3D printing technology with Agilus30 (flexible phase) and VeroMagentaV (rigid ...phase) materials. Mechanical properties were evaluated through tensile and compression tests. The general rule of mixture (ROM) for composites was employed to approximate the tensile properties of the hybrid materials and compare them to the experimental results. The effect of reinforcement alignments and different hierarchies are discussed. The results indicated that the 5% inclusion of the Peano reinforcement in tensile samples contributed to the improvement in the elastic modulus by up to 6 MPa, but provided no obvious enhancement in ultimate tensile strength. Additionally, compressive strengths between 2 MPa and 6 MPa were observed for compression cubes with first-order reinforcement, while lower values around 2 MPa were found for samples with second-order reinforcement. That is to say, the first-order reinforcement has been demonstrated more effectively than the second-order reinforcement, given the same reinforcement volume fraction of 10% in compression cubes. Different second-order designs exhibited slightly different mechanical properties based on the ratio of reinforcement parallel to the loading direction.
Abstract
The paper proposes a class of tunable metamaterials that use inclined beams to achieve instability in a rigid system. Three different beam tilt angles, 25°, 45°, and 60°, are evaluated in ...the form of unit cells using quasi-static compression tests and numerical simulations. Snap-through behavirous are characterised by structural stiffness and buckling load. Periodic and gradient structures are assembled and analysed by arranging the unit cells in rows and columns. Size effect analyses and parametric studies are carried out on various unit-cell arrangements and different beam angles. The proposed metamaterials are manufactured through fused filament fabrication 3D printing technology with a composite material, onyx. The results from experiments, finite element analysis, and analytical models are compared and evaluated. The structural stiffness and buckling load are shown to be positively related to the inclination angle of the tilted beams. The number of rows of unit cells governs the nonlinear mechanical response (number of snap-throughs) of multiple-layered structures. By increasing the number of rows and columns of unit cells, which are less prone to manufacturing defects, the reliability and repeatability of the structural properties of periodic/gradient structures could be improved. A design plot is also provided to predict and tune the snap-through behaviour of multiple-layered structures via beam angles and unit-cell arrangements.
Cellular structures with tunable mechanical properties are promising lightweight structures for prefabricated construction. In this study, a 3D fractal structure named Menger-Sponge (MS) cube is ...analysed. Besides, six other alternative fractal-like structures are designed with respect to different shapes of their associated hollow sections. Finite element method (FEM) is employed to predict the structure's mechanical behaviours under a uniaxial compression load. The numerical model is validated by experimental results obtained from author's previous publication. Comparisons are made between triply periodic minimal surface (TPMS-Primitive) and the second-order MS cementitious structure, and also among other fractal structures with different hierarchies. Results indicate that the MS and Primitive blocks have similar mechanical responses. The fractal-square (FS) structures exhibit better structural performances, especially for the first and second fractal orders. Overall, this numerical investigation shows the effect of the shaped holes and thinnest cross-section area on the hierarchically porous structure.
Composites materials and structures are increasingly used to replace conventional materials in civilian and defence-related maritime transportation and infrastructure such as naval vessels, ...submarines, civilian ships, and oil platforms for its better performance-to-weight ratio and electro-magnetic signature control. However, when subjected to under water explosions (UNDEX), navel composite structures experience highly nonlinear deformations and damages. Such transient deformation phenomena of composites and associated multiscale damages have been a subject of research for many years. This review aims to provide historical and methodological overviews of significant research and contributions in this area over the last 20 years from experimental programs, modelling approaches, post-mortem analysis techniques, analytical approximation and recently emerging area of data-led predictive simulations. UNDEX event is often described by a series of events including (a) the formation of the arriving shock wave, (b) the attenuation of the initial shock wave, (c) development of cavitation due to the reflected tension wave from free surface or the structural obstacles, (d) fluid-structure interaction-induced deformation and associated (e) cavitation coalescence and collapse. Such interconnected dynamic events and their influences on the behaviours of composite structures are subjected to extensive research and therefore summarised in this review work to highlight state-of-the-art field and laboratory-scaled experimental programs including investigations on low temperature and cavitation’s influences. Furthermore, the ongoing increase in the computing power and the development of advanced numerical methods have made it possible for multiscale and multi-physics simulations capturing the complex fluid dynamics associated with UNDEX. Over ten different modelling approaches, hydrocodes and their hybrid combination are summarised and discussed for potential applications. Review on current computational approaches also reveals the shortcomings of predictive modelling due to unavoidable simplifications, empirical assumptions on limited experimental data. Therefore, this work also provides a brief discussion on how data-led modelling approach such as artificial neural networks or deep learning, which is based largely on experimental data, could provide powerful assistance to analytical and deterministic numerical analysis.
A novel 2D polyoxometalate framework is obtained from Zn2+-directed assembly of the new Zn3.2Bi0.8(B-a-ZnW9O34)215− building block. Electrochemical behavior of the compound (1) is studied by cyclic ...voltammetry (CV) in sodium acetate buffer solution. Moreover, compound (1) also can act as a catalyst in the oxidation of cyclohexanol with hydrogen peroxide.
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A new sandwiched polyoxometalate Na2Zn4H5Zn3.2Bi0.8(B-α-ZnW9O34)2·52H2O {Zn3.2Bi0.8} (1) was synthesized from one-pot transformations of the trilacunary Keggin-type B-α-BiW9O339− precursor via Bi/Zn exchange, followed by self-assembly of the sandwich-type polyanions. The {Zn3.2Bi0.8} polyanion was further self-assembled into 2D architecture by adjusting Zn2+ and Na+ cations. The compound (1) was characterized with a wide range of analytical methods, including single crystal and powder X-ray diffraction, thermogravimetric analysis and various spectroscopic techniques (FT-IR, Raman, UV–Vis). Electrochemical behavior of the compound (1) was also studied by cyclic voltammetry (CV) in sodium acetate buffer solution. Moreover, compound (1) also can act as a catalyst in the oxidation of cyclohexanol with hydrogen peroxide.
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