Papers by Keyword: Multiphase Material

Abstract: Several investigations regarding the mechanical behaviour of composites reinforced by natural fibers under impact have been realized recently, aiming at achieve a low-weight and resistant design. At the same time, progressively accurate results on numerical simulations have been reached powered by modern Finite Element Method (FEM) approaches for composites; however, demonstrating a faithful indentation pattern is still a challenge. The present work aims at building an impact numerical simulation that exhibits a fracture mechanism exactly like the one seen in experimental tests, also carried in this work, on a Basalt Reinforced Composite Polymer (BRFP) plate subjected to low-velocity falling weight impact (IFW). The FEM simulation describes a multiphase model considering each ply and their inter-layer interactions.

Abstract: This study focuses on the modeling of damage in concrete subject to sulfate attack. The concrete is described as a multiphase material made of a solid skeleton, a fluid phase including water and air and an expanding phase, which exerts a pressure capable of damaging the concrete surrounding the reactive sites. The moisture content is computed through a simplified diffusion model, then a reactive-diffusion model allows for the computation of the expansive products of the reaction occurring between the aluminates of the cement paste and the incoming sulfate ions.

Abstract: A new hybrid FRP wrapped anchor is developed to solve the poor ductility of FRP anchor. The designability of functionally graded material (FGM) makes it possible to connect the high ductility metal to FRP material. Numerical and analytical methods are compared in solving plane stress FGM cantilever beam problem. The results show the analytical method's simplification in constraint makes it inaccurate in solving displacements. Consequently, the numerical method is employed to analyze the hybrid FRP wrapped anchor in the ideal condition. The results indicate the hybrid FRP wrapped anchor solved the current problem theoretically.

Abstract: The microstructure design satisfying the mass constraint can reduce the structure weight more directly and effectively in comparison with the volume constraint. This paper is devoted to the topology optimization of microstructures with multiphase materials under the mass upper limitation constraint for maximizing the equivalent elastic tensors and their combinations. Firstly, the strain energy method is applied to compute the effective elastic properties of microstructures. In order to make sure that the formulation of mass constraint is linear with separable design variables, DMO (Discrete Material Optimization) model is adopted for the element density interpolation. Therefore, this optimization problem can be solved efficiently by means of mathematical programming approaches, especially the convex programming methods. Besides, the filtering technique is adopted to avoid the checkerboard pattern. There are two categories of numerical examples. In the first category, the modulus and the stiffness ratio of the solid material phase 1 are smaller than the solid material phase 2. In the second category, the modulus of the solid material phase 1 is still smaller than the solid material phase 2, but its stiffness ratio is bigger than the solid material phase 2.

Abstract: The scope of this work is the determination of single-crystals elastic constants (SEC) from X-ray diffraction lattice strains measurements performed on multi-phase polycrystals submitted to mechanical load through a bending device. An explicit three scales inverse self-consistent model is developed in order to express the SEC of a cubic phase, embedded in a multi-phase polycrystal, as a function of its X-ray Elasticity Constants. Finally, it is applied to a two-phases (α+β) titanium based alloy (Ti-17), in order to estimate Ti-17 β-phase unknown SEC. The purpose of the present work is to account the proper microstructure of the material. In particular, the morphologic texture of Ti-17 a-phase, i.e. the relative disorientation of the needle-shaped grains constituting this phase, is considered owing to the so-called Generalized Self-Consistent model.

Abstract: The lattice fracture model is presented in this paper, which is intended to simulate the fracture processes in multiphase materials to obtain the mechanical behavior in terms of load-displacement diagram and the cracks propagation. The basic procedures of lattice fracture analysis is that imposing a prescribed displacement on a lattice structure, finding the critical lattice element with the highest stress/strength ratio, removing it from the system and repeating until the system fails globally. One of the challenges in computer implementation of 3D lattice fracture model is the huge demand for computer memory. Matrix free technique is adopted to solve this problem.

Abstract: The output quantity of iron tailings increases rapidly with the development of metallurgical industry and the growth of the requirement for minerals in the world, which could cause severe hazard to our environment. Therefore, it is very important to recover and reuse these tailings to protect the environment and use natural resources effectively. In this paper, the Fe-Si-Ti multiphase composite ceramic has been synthesized from the Iron ore tailings of Panzhihua region with the carbothermal reduction nitridation (CRN) method. The phases and microstructures of sintered body were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FSEM) and energy dispersive spectroscopy (EDS). The XRD pattern indicates that the main phases of the samples are Fe3Si and Ti(C0.3, N0.7). Meanwhile, FSEM and EDS show that Fe3Si is surrounded by Ti(C0.3, N0.7). Besides, the physical properties of the sample are tested, especially the wear resistance. The test results show that the synthesized Fe3Si-Ti(C0.3, N0.7) composite ceramic has good wear resistant property, high hardness and larger thermal expansion coefficient, which indicates it can be used as the abrasion-proof material or transition layer between the metal and inorganic coating. At last, based on FSEM and EDS, the microstructure and elements of the abraded surface of sample is analyzed.

Abstract: The main problems for multiphase materials are the even mixing and the bonding or reacting among two or more phases, as well as the states of their grain boundaries. The mixing of two phases is usually effective by using liquid medium. The technology of second phase coating for the original particles or so call nucleo-shell structure is a well approach for the even mixing. For ceramic matrix multiphase materials low sintering temperature is the effective way to avoid the occurring of reaction between different phases. The design of grain boundary and its stress is important for their bonding states. The thinking for above problems would be described briefly in this paper. The purpose of multiphase materials design is expected that every phase will be playing its role, combining together and then given out a comprehensive performances. So it is necessary to consider the following problems. 1. Even mixing Even mixing between each other material is important for multiphase materials. It’s the better when the processing is carrying on in the liquid state for the even mixing of two phase materials. Using physical or chemical method could be formed the fine solid particles with even dispersion of two or more phases materials. Usually it could be obtained nano-scale particles. The application of nano-technology is necessary. The nano-scale mixing of two phases materials would be greatly increased the contacting surface of each other particles without agglomeration. Of course, if one phase of material is fine solid particle which disperses in another phase of material solution, the even mixing of two phases is obtained similarly. Making a coating to other phase particle is a very good approach for the two phases even mixing. Coating process is attracting more and more attention in the preparation of composite materials mainly due to its predominance in the improvement of the uniformity for different phases [1]. The thickness of coating material determines the amount proportion of two phases which is able to be control. Two examples of so-called “nucleo-shell structure” will be introduced in the following parts. Cermet composites have been widely studied due to their potential for achieving higher toughness and reasonable strength compared with ceramic matrix. But except for numbered systems, such as Co/WC and Ni/TiN, few systems have reached the people’s expectation mainly for the poor wettability between metal and ceramic. Al/Al2O3 cermet is a low density and high strength material, and it has many potential and actual applications in military, industrial and consumer regions. To improve the dispersive uniformity of the two phases, coating aluminum with alumina may be a good candidate since such coatings not only stabilize aluminum dispersions but also make it possible to control inter-particle and particle-matrix interactions [2]. Figure1a-c shows the images