Papers by Keyword: Infiltration

Abstract: Closed mold injection processes such as resin transfer molding have an increasing importance for manufacturing high quality carbon fiber reinforced parts at high production rates. One major challenge during this process is to avoid resin rich corners, which are a result of a non-uniform compaction of the preform in the tool. The objective of this work is to predict compaction defects in the preform and their effects on the filling behavior. We use numerical compaction simulations to calculate the preform geometry after tool closing, which is subsequently transferred into the infiltration simulation to model the filling behavior. Additionally, the fiber volume content and the material orientations are transferred from the mechanical simulation. Areas in the tool, which are not filled by the reinforcement, are modelled as flow channels with high permeability. The achieved results prove the significant influence of the compaction state on the filling behavior. The novel method supports the design of RTM tools and helps to optimize the manufacturing process.

Abstract: Hybrid material structures allow different material properties to be combined in one single component and thus to meet high functional requirements. When manufacturing such hybrid components, particular attention must be paid to the transition zones between metallic composite partners. These transition zones need to show largely homogeneous and materially bonded structures in order to ensure ideal transmission of the material properties and to prevent component failure due to material defects. In this respect, this paper focuses on a newly developed process in which a powder metallurgical route is combined with semi-solid forming technology. Here, porous copper green bodies are inserted into a forming die and subsequently forged together with a semi-solid aluminium alloy. In this way, it was tried to combine both metal materials into a material locking or at least into a form locking manner in order to achieve ideal material properties in the final hybrid component. The aim of this paper is to find suitable process parameters to infiltrate the porous copper inlay with the semi-solid aluminium alloy during thixoforming. Therefore, different process parameters such as varying liquid fraction of the aluminium alloy and different densities of the green bodies were examined during the production of simply shaped hybrid Al-Cu-components. Afterwards the infiltration depth and produced microstructure of the components was analysed. In the future, this process allows for producing aluminium-copper hybrid heat sinks with improved heat transfer properties compared to conventional produced heat sinks.

Abstract: Gypseous soil disturbed in many regions in the world. Existence of this soil with high gypsum content caused many damages to the buildings and structures that built on it due to dissolve and leaching of the gypsum slates by the flow of water through the soil mass. Therefore, it is necessary to study the properties of such soil. The dissolve of gypsum depends on many factors such as (gypsum content, temperature and other factors). Another important factor which is the acidity of the dissolution liquid must be considered. This study observes the influence of Acetic acid (CH3COOH) on the gypseous soil. Laboratory models includes (270 mm diameter) and (500 mm height) thick steel cylinder container and 17.1 kN/m3 density gypseous soil compacted in three layers, with gypsum content about 58% . The relation between the soaking time and the shear strength parameters was investigated. Also, plastic square container dimensions (250 mm x 250 mm x 300mm) used with same conditions to observed the deformation of the soil. The aim of this study is to simulate the infiltration of Acid in Gypseous soil. Test results show that increase cohesion of soil for diluted acid while decrease cohesion values for concentrated acid. Angle of friction for soil was increase for diluted and concentrated acid.

Abstract: CMAS attack is known to occur owing to the deposition of volcanic ash onto thermal barrier coating (TBC) surface at a high-temperature environment. The serious problem is TBC spallation resulting from the infiltration of molten volcanic ash into the porous microstructure of TBC. The infiltration induces inner stress and phase transformation, which directly results in those serious problems. In this study, the diffusional equation for expressing the infiltrating process of the molten ash into the porous structure of TBC and the associated constitutive equation considered regarding phase transformation are formulated. The equations are installed into commercial finite element (FE) code (MARC) using the user subroutine. The numerical simulation results are compared with the cross-sectional SEM observation for the volcanic-ash-deposited TBC sample exposed at a high-temperature to confirm verification of the model proposed herein.

Abstract: The hydrogen is promising energy carrier due to its high energy density, convenient transportation, eternal sources in the earth and cleanness. Solid oxide fuel cells (SOFCs) have not been commercialized yet even though it has been studied for decades. The issues about solid oxide fuel cells are manufacturing process and electrochemical performance. Tape-casting process has an advantage of cost reduction for mass production. it is reported that infiltration improves electrochemical performance of SOFCs by enhancing the three phase boundary (TPB) and porosity. To fabricate the electrode with porous scaffold structure for infiltration, pore formers were added in the tape-casting slurry. In this study, four types of mixtures of several pore formers such as carbon black, graphite, poly methyl methacrylate and glassy carbon were estimated. Micro structure of each type is investigated through scanning electron microscope (SEM). The thickness of the unit cell manufactured by tape-casting is in the range of 200 - 250 μm. The fabricated unit cell with carbon black and glassy carbon shows the open circuit voltage 1.07 V at 800°C. As a result of the study, mixed ratio of pore formers was researched for Solid Oxide Fuel Cells manufacturing process applied by tape-casting and infiltration method.

Abstract: The airtightness performance of dilapidated dwellings is low. Infiltration occurs due to such low airtightness performance, causing the energy loss. Energy loss due to infiltration accounts for more than 30% of total energy loss in a building. Therefore, the airtightness performance should be considered by priority when retrofit of dilapidated dwelling is carried out. To improve the airtightness performance, numerous studies are underway. As a result, various products have been developed. The purpose of this study is to evaluate the performance of windbreak for improving the airtightness performance of dwelling and analyze the improvement level of airtightness performance of the room quantitatively after the windbreak is actually applied to dilapidated dwelling. In order to measure the airtightness performance of window where windbreak was applied, we measured the airtightness performance of window before and after windbreak was applied. Also, for the field performance evaluation, 27 dwellings were selected to measure the airtightness performance of the windbreak applied room. The measurement result showed that the infiltration rate of window where windbreak was applied decreased by approximately 48.66% in comparison to that before the windbreak was applied. And, The ACH₅₀ (Air Change per Hour at 50 pascals of pressure) of the room where the windbreak was applied decreased by approximately 31.61%, confirming that the airtightness performance of window was improved through the application of windbreak.

Abstract: The matrix graphite of fuel elements (FEs) with infiltration of 2LiF-BeF₂(FLiBe) at different pressures varying from 0.4 MPa to 1.0 MPa, has been studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and positron annihilation lifetime (PAL) measurement. The result of XRD reveals that diffraction patterns of FLiBe appear in matrix graphite infiltrated with FLiBe at a pressure of 0.8 MPa and 1.0 MPa. The surface morphology from SEM shows that FLiBe mainly distributes within macro-pores of matrix graphite. PAL measurement indicates that there are mainly two positron lifetime components in all specimens:τ₁~0.21 ns and τ_{2 ­}~0.47 ns, ascribed to annihilation of positrons in bulk and trapped-positrons at surface, respectively. The average positron lifetime decreases with infiltration pressure, due to the decrease in annihilation fraction of positrons with surface after infiltration of FLiBe into macro-pores.

Abstract: A series of advantages for resin matrix composites make it get extensive application in PCB Field. However, because the properties of composites depend on process crafts badly,unreasonable processing technology will lead forming difficult, and then redesign is needed. This affects production efficiency badly in PCB enterprise. According that composites forming process is huge and complicated, in order to evaluate whether it is rensonable on produce process. This paper try to discuss the technical method of improving the wettability of the composite material from the angle of the production process by increasing the infiltration area, gradually exhaust, increasing the total amount of the base material, pressure infiltration velocity difference and improve the shortcomings in the material production process review. This paper validates the methods useful and practical. It can get a better production effect of infiltration by increasing infiltration area, step by step exhaust, increasing the total matrix materials, speed difference infiltration, pressure type wait for infiltration. The rapid infiltration production technology not only improves the performance of composite materials, but also has important significance to improve the interfacial properties of the composites.

Abstract: The paper presents the problem of windwashing in partitions including air permeable thermal insulations. There are technical solutions, which deliberately accept the filtration of air in the insulating layer, guided by the necessity of possible drying of building materials. Some scientific papers even suggest that the air infiltration decrease the heat losses through ventilation. In result there occur heat losses in building heat balance which are underestimated and therefore difficult to take into account during calculations. Heat changes on the inner surface of the building partition occur with a delay to the initiation of the wind. However, even the short-term local wind speed loads on thermal insulations result in temperature decreasing and therefore possible condensation on the inner surface of the building partition. The article presents laboratory measurements of air permeability of loose mineral wool and laboratory investigation of the impact of air filtration on heat transfer in lightweight partitions filled with loose thermal insulation.

Abstract: This work developed a ceramic material for dental application, spinel-base (MgAl₂O₄), a ceramic material with recognized translucency. Spinel powders were uniaxially pressed at 100 MPa and pre-sintered in order to obtain porous ceramic blocks. The pre-sintered blocks were characterized and indicated 80% of relative density. X-ray diffraction (XRD) only showed MgAl₂O₄ phase. Samples with 15 x 15 x 1 mm were submitted to infiltration using glass rich in lanthanum (La). The products were characterized by scanning electron microscopy (SEM) and mechanical properties, as hardness and fracture toughness. Results were compared to the commercial product VITA-InCeram Spinell. Relative densities exceeding 92%, hardness around 900 HV and high toughness 2.5 MPa.m^1/2 were obtained for both examined systems.